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Sökning: L773:0039 9140 OR L773:1873 3573

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1.
  • Andersson, Helene, et al. (författare)
  • Self-assembled and self-sorted array of chemically active beads for analytical and biochemical screening
  • 2002
  • Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 56:2, s. 301-308
  • Tidskriftsartikel (refereegranskat)abstract
    • A technique for generating a general screening platform consisting of dots of immobilized beads on silicon has been developed via self-sorting and -assembly of different kinds of beads. The dots are defined by a teflon-like film, which due to its hydrophobic characteristics also prevents cross-contamination of liquid from different dots. To enable functionalization of individual dots with different target molecules simultaneously a new way of microcontact printing has been explored where different target solutions are printed in parallel using one stamp. In order to show that this platform can be designed for both biochemical assays and organic chemistry, streptavidin-, amino- and hydroxy-functionalized beads have been self-sorted and -assembled both on separate and common platforms. The self-sorting and -arrangement are based on surface chemistry only, which has not previously been reported. Beads of different sizes and material have successfully been immobilized in line patterns as narrow as 5 mum. Besides silicon, quartz and polyethylene have also been used as substrates.
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2.
  • Andersson, Marit, et al. (författare)
  • A modified standard addition method in X-ray fluorescence spectrometry
  • 1993
  • Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 40:5, s. 669-674
  • Tidskriftsartikel (refereegranskat)abstract
    • A modified standard addition method for single element determination by X-ray fluorescence spectrometry has been studied. The attenuation properties of the standard added samples are kept constant by adding decreasing amounts of an attenuation modifier along with increasing amounts of a standard. In this way the standard addition curve will be a straight line in cases where the ordinary standard addition curve is non-linear, and linear regression can be used to evaluate the concentration of the analyte. Standard additions of oxides of a number of elements, with and without modifier, have been made to cellulose powder or a mixture of aluminium oxide and polyethylene as matrices in order to test the method. The method has been applied to the determination of zinc in fly-ash from a steel work and of iron in cement. The fly-ash contained about 5% of zinc and the cement samples between 2 and 5% of Fe(2)O(3). The results were compared with those obtained by ICP-AES after decomposition of samples in lithium tetraborate or lithium metaborate and dissolution of the melt in 10%(v/v) nitric acid. The results agreed within 2%, relative, for fly-ash and within 3-6%, relative, for cement samples.
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3.
  • Andersson, Marit, et al. (författare)
  • Determination of bromine, chlorine, sulphur and phosphorus in peat by X-ray fluorescence spectrometry combined with single-element and multi-element standard addition
  • 1990
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 37:2, s. 185-191
  • Tidskriftsartikel (refereegranskat)abstract
    • Bromine (20-40 ppm), chlorine (200-500 ppm), sulphur (0.2-3%) and phosphorus (300-1000 ppm) in peat have been determined by X-ray fluorescence spectrometry (XRFS) combined with the standard-addition method. Chlorine, sulphur and phosphorus have also been determined by other methods and agreement between the results is good. Theoretical calculations based on the Sherman equation were made to validate the linearity of the standard-addition curves. A multi-element standard-addition technique has been tested with addition of all elements at the same time. The results for chlorine were high but after correction for the difference in attenuation coefficient between the sample and added compound the results agreed with those from single-element standard addition.
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4.
  • Andersson, Marit, et al. (författare)
  • Determination of lead in fly-ash from a garbage incinerator by atomic-absorption and x-ray fluorescence spectrometry
  • 1988
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 35:5, s. 337-41
  • Tidskriftsartikel (refereegranskat)abstract
    • The lead content in fly-ash collected by an electrostatic precipitator has been determined by atomic-absorption spectrometry (AAS) after decomposition by four different leaching/dissolution techniques, and also determined by X-ray fluorescence spectrometry (XRFS) by the standard-addition method. The XRFS data were evaluated by non-linear regression since the standard additions affected the attenuation coefficient of the sample. Good agreement was obtained between the results obtained with AAS and XRFS. It is concluded that lead is quantitatively extracted by hot 1M nitric acid or treatment with hydrofluoric acid/nitric acid. Direct measurement of briquetted samples by XRFS is suggested for rapid monitoring of the lead content in fly-ash from garbage incineration.
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5.
  • Andersson, Marit, et al. (författare)
  • Determination of lead in household refuse fly-ash by X-ray fluorescence spectrometry and a modified standard-addition technique
  • 1991
  • Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 38:4, s. 385-390
  • Tidskriftsartikel (refereegranskat)abstract
    • Lead in fly-ash from a garbage incinerator has been determined by X-ray fluorescence spectrometry (XRFS) and a modified standard-addition method. To keep the attenuation properties of the spiked samples constant, decreasing amounts of an attenuation modifier [mercury (II) acetate] were added together with increasing amounts of the standard (lead nitrate). Linearity between fluorescence intensity and amount of lead was thus obtained, so the amount of lead in the sample could be evaluated by linear regression. The amount of modifier needed could be calculated from a simple expression. The method was validated by comparison with the results obtained by applying atomic-absorption spectrometry (AAS) to solutions made by leaching the fly-ash with strong acid. For 8 fly-ash samples, containing between 0.8 and 1.35% lead, the largest absolute difference between the two sets of results was 0.03%. Theoretical calculations based on a simplified version of the Sherman equation were performed to confirm the linearity of the modified standard-addition curves.
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6.
  • Ericzon, Christina, et al. (författare)
  • Interference from iodide in the determination of trace level selenium
  • 1990
  • Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 37:7, s. 725-730
  • Tidskriftsartikel (refereegranskat)abstract
    • The rate of the reaction between iodide and selenium(IV) at trace levels to form selenium and iodine has been determined in 1–6M hydrochloric acid. The reaction rate increases rapidly with acidity. When hydrochloric acid is added to reduce selenate to selenite prior to the determination of total selenium, some selenium may be lost by reduction to the element if iodide is present. A table of half-lives of the selenite—iodide reaction under various conditions is presented. A method for removal of iodide is suggested.
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7.
  • Rodushkin, Ilya, et al. (författare)
  • Multielement analysis of coal by ICP techniques using solution nebulization and laser ablation
  • 2000
  • Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 51:4, s. 743-759
  • Tidskriftsartikel (refereegranskat)abstract
    • The combination of inductively coupled plasma atomic emission spectrometry and high resolution inductively coupled plasma mass spectrometry for the determination of 70 elements in coal were studied. Four microwave-assisted digestion procedures with different dissolution mixtures (nitric and hydrofluoric acids, aqua regia and hydrogen peroxide), lithium metaborate fusion with and without previous sample ashing as well as direct sampling by laser ablation (LA) have been tested. Examples of spectral interferences are given and different correction procedures are discussed. Detection limits in the low ng g-1 range were obtained for most of the elements investigated by using high-purity reagents and by taking special care to prevent sample contamination during preparation. The precision was assessed from replicate analysis (including sample preparation) of coal samples and was found to be, as average values far all elements, 4-5% RSD and 10-15% RSD for procedures including sample digestion and LA sampling, respectively. The accuracy of the overall analytical procedures was estimated by analysis of certified reference materials and of a coal sample obtained from the Interlab Trace round robin test. Among the dissolution mixtures tested, the combination of nitric and hydrofluoric acids with hydrogen peroxide provide the best agreement with certified, recommended, literature-compiled or consensus values, though fusion is necessary to obtain quantitative recoveries for Si, Cr, Hf, W, Zr, Y. In general, results obtained by LA fall within ±20% of those obtained after digestion.
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8.
  • Tóth, I., et al. (författare)
  • Application of a sulphide-selective electrode in the absence of a pH-buffer
  • 1988
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 35:10, s. 783-788
  • Tidskriftsartikel (refereegranskat)abstract
    • Calibration of a sulphide electrode in the pH-range 9-12 has been studied as an e.m.f. vs. (pH - p[HS-]) function by measuring e.m.f. and pH in parallel. Calibration can also be done in this pH range by using a differential amplifier with a three-electrode measuring cell (glass, sulphide-selective and reference electrodes). The effects of an antioxidant (ascorbic acid) and a complexing agent (DCTA) on the calibration of the glass-sulphide electrode cell at pH < 5 were studied. The applicability of this end-point indicator cell has been demonstrated for titrations of Ag+, Pb2+ and Bi3+ with Na2S.
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9.
  • Tóth, I., et al. (författare)
  • Extraction of gallium(III) and aluminium(III) with O,O-dialkyldithiophosphoric acids
  • 1990
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 37:12, s. 1175-1178
  • Tidskriftsartikel (refereegranskat)abstract
    • The extraction of Ga3+ and Al3+ with the liquid cation-exchangers di-n-butyldithiophosphoric acid (DBTPA) and di-(2-ethylhexyl)dithiophosphoric acid (DETPA) in kerosene, in the presence and absence of alcohols and tri-n-butyl phosphate (TBP) has been studied. Both Ga3+ and Al3+ can be extracted in the form of a neutral complex, MA3, but the distribution coefficient of Ga3+ is the higher by about two orders of magnitude, which can be the basis of the solvent extraction separation of gallium and aluminium. The differences can be explained by the interaction between the sulphur donor atoms of the extractants and the d10 electronic shell of Ga3+ as well as by the lower steric hindrance of ligands co-ordinated to Ga3+. 
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10.
  • Adeniyi, Omotayo, et al. (författare)
  • Reagentless impedimetric immunosensor for monitoring of methotrexate in human blood serum using multiwalled carbon nanotube@polypyrrole/polytyramine film electrode
  • 2024
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 268:Part 1
  • Tidskriftsartikel (refereegranskat)abstract
    • Ensuring effective monitoring of methotrexate (MTX) levels in the bloodstream of cancer patients undergoing high-dose methotrexate chemotherapy is crucial to prevent potentially harmful side effects. However, the absence of portable analytical devices suitable for point-of-care bedside monitoring has presented a significant obstacle to achieving real-time MTX monitoring. In this study, we developed an impedimetric immunosensor that doesn't require reagents for measuring MTX levels in undiluted human blood serum. This reagentless approach simplifies the assay process, enabling rapid and straightforward MTX quantification. The immunosensor transducer was fabricated by electrodepositing conductive network of porous multiwalled carbon nanotube@polypyrrole/polytyramine on screen-printed gold microchip electrode (SP–Au/MWCNT70@PPy-PTA). Polyclonal anti-MTX antibodies were immobilized on the film, acting as the immunorecognition element. Non-specific binding was prevented by blocking the transducer interface with denatured bovine serum albumin (dBSA) fibrils, resulting in SP-Au/MWCNT70@PPy-PTA/anti-MTXAb|dBSA film electrode. When MTX binds to the SP-Au/MWCNT70@PPy-PTA/anti-MTXAb|dBSA interface, the film conductance and electron transfer resistance changes. This conductivity attenuation allows for electrochemical impedimetric signal transduction without a redox-probe solution. The electrochemical impedance spectroscopy (EIS) results showed increased charge transfer resistance and phase angle as MTX concentrations increased. The SP-Au/MWCNT70@PPy-PTA/anti-MTXAb|dBSA demonstrated high sensitivity, with a linear response from 0.02 to 20.0 μM and a detection limit of 1.93 nM. The detection limit was 50 times lower than the intended safe level of MTX in human serum. The immunosensor exhibited minimal cross-reactivity with endogenous MTX analogs and serum proteins. The SP-Au/MWCNT70@PPy-PTA/anti-MTXAb|dBSA immunosensor presents a simple and rapid method for therapeutic drug monitoring compared to traditional immunoassay systems.
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11.
  • Akhdhar, Abdullah, et al. (författare)
  • The use of high resolution graphite furnace molecular absorption spectrometry (HR -MAS) for total fluorine determination in extractable organofluorines (EOF)
  • 2020
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 209
  • Tidskriftsartikel (refereegranskat)abstract
    • The determination of total fluorine content using high-resolution graphite furnace continuum source molecular absorption spectrometry (HR- MAS) has been employed in a variety of samples for over 10 years. However, most of the samples analysed by HR-MAS are rich in fluoride, with negligible levels of organic fluorinated species. With an increase in concern surrounding per- and polyfluoroalkyl substances (PFASs), new methods to measure total fluorine of organofluorine using different techniques have been developed. However, no studies focused on PFASs behaviour in HR-MAS have been performed. As these compounds encompass a wide range of different structures, boiling points, decomposition temperatures and matrix interactions, a loss of accuracy can occur when an aqueous external calibration is performed using only one compound. To overcome this issue, an investigation into permanent modifiers for the graphite furnace was performed. After optimisation similar sensitivity for different PFCA was achieved when 400 mu g of W was used as a permanent modifier together with an optimised temperature program. The relative deviation between the different PFCA standard slopes relative to the PFOA slope was lower than 15%. The instrumental limit of detection and quantification (LOD and LOQ, respectively) of total fluorine as total PFCA was 0.1 mg L-1 and 0.3 mg L-1, respectively, while the method LOD and LOQ (using solid phase extraction) was 0.3 mu g L-1 and 1.0 mu g L-1, respectively. The developed method gave satisfactory recoveries for the spiked PFCA into seawater, river water and effluent using PFOA calibration standards. The optimised method is useful for measuring extractable organofluorines (EOF) when only ionic PFASs such as PFCA are expected. When other organofluorines are expected, the results using HR GF-MAS should be taken with caution.
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12.
  • Ali Kamyabi, Mohammad, et al. (författare)
  • A high-performance glucose biosensor using covalently immobilised glucose oxidase on a poly(2,6-diaminopyridine)/carbon nanotube electrode
  • 2013
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 116, s. 801-808
  • Tidskriftsartikel (refereegranskat)abstract
    • A highly-sensitive glucose biosensor amenable to ultra-miniaturisation was fabricated by immobilisation of glucose oxidase (GOx), onto a poly(2,6-diaminopyridine)/multi-walled carbon nanotube/glassy carbon electrode (poly(2,6-DP)/MWNT/GCE). Cyclic voltammetry was used for both the electrochemical synthesis of poly-(2,6-DP) on the surface of a MWNT-modified GC electrode, and characterisation of the polymers deposited on the GC electrode. The synergistic effect of the high active surface area of both the conducting polymer, i.e., poly-(2,6-DP) and MWNT gave rise to a remarkable improvement in the electrocatalytic properties of the biosensor. The transfer coefficient (alpha), heterogeneous electron transfer rate constant and Michaelis-Menten constant were calculated to be 0.6, 4 s(-1) and 0.20 mM at pH 7.4, respectively. The GOx/poly(2,6-DP)/MWNT/GC bioelectrode exhibited two linear responses to glucose in the concentration ranging from 0.42 mu M to 8.0 mM with a correlation coefficient of 0.95, sensitivity of 52.0 mu AmM-1 cm(-2), repeatability of 1.6% and long-term stability, which could make it a promising bioelectrode for precise detection of glucose in the biological samples. (C) 2013 Elsevier B.V. All rights reserved.
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13.
  • Ali Kamyabi, Mohammad, et al. (författare)
  • Correction: A high-performance glucose biosensor using covalently immobilised glucose oxidase on a poly(2,6-diaminopyridine)/carbon nanotube electrode (vol 116, pg 801, 2013)
  • 2016
  • Ingår i: Talanta. - : ELSEVIER SCIENCE BV. - 0039-9140 .- 1873-3573. ; 153, s. 414-415
  • Tidskriftsartikel (refereegranskat)abstract
    • A highly-sensitive glucose biosensor amenable to ultraminiaturisation was fabricated by immobilization of glucose oxidase (wGOX), onto a poly(2,6-diaminopyridine)/multi-walled carbon nanotube/glassy carbon electrode (poly(2,6-DP)/MWCNT/GCE). Cyclic voltammetry was used for both the electrochemical synthesis of poly-(2,6-DP) on the surface of a MWCNT-modified GC electrode, and characterization of the polymers deposited on the GC electrode. The synergistic effect of the high active surface area of both the conducting-polymer, i.e., poly-(2,6-DP) and MWCNT gave rise to a remarkable improvement in the electrocatalytic properties of the biosensor. The transfer coefficient (alpha), heterogeneous electron transfer rate constant and Michaelis-Menten constant were calculated to be 0.6, 4 s-1 and 0.22 mM at pH 7.4, respectively. The GOx/poly(2,6-DP)/MWCNT/GC bioelectrode exhibited two linear responses to glucose in the concentration ranging from 0.42 mu M to 8.0 mM with a correlation coefficient of 0.95, sensitivity of 52.0 mu AmM-1 cm-2, repeatability of 1.6% and long-term stability, which could make it a promising bioelectrode for precise detection of glucose in the biological samples. (C) 2016 Elsevier B.V. All rights reserved.
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14.
  • An, Siwen, et al. (författare)
  • Signal-to-Noise Ratio Optimization in X-ray Fluorescence Spectrometry for Chromium Contamination Analysis
  • 2021
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 230
  • Tidskriftsartikel (refereegranskat)abstract
    • In most cases, direct X-ray fluorescence (XRF) analysis of solutions entails technical difficulties due to a high X-ray scattering background resulting in a spectrum with a poor signal-to-noise ratio (SNR). Key factors that determine the sensitivity of the method are the energy resolution of the detector and the amount of scattered radiation in the energy range of interest. Limiting the width of the primary spectrum by the use of secondary targets, or filters, can greatly improve the sensitivity for specific portions of the spectrum. This paper demonstrates a potential method for SNR optimization in direct XRF analysis of chromium (Cr) contamination. The suggested method requires minimal sample preparation and achieves higher sensitivity compared to existing direct XRF analysis. Two states of samples, fly ash and leachate from municipal solid waste incineration, were investigated. The effects of filter material, its absorption edge and filter thickness were analyzed using the combination of Monte Carlo N-Particle (MCNP) code and energy-dispersive XRF spectrometry. The applied filter removes primary photons with energies interfering with fluorescence photons from the element of interest, thus results in lower background scattering in the spectrum. The SNR of Cr peak increases with filter thickness and reaches a saturation value when further increased thickness only increases the measurement time. Measurements and simulations show that a Cu filter with a thickness between 100 μm and 140 μm is optimal for detecting Cr by taking into account both the SNR and the exposure time. With direct XRF analysis for solutions, the limit of quantitation (LOQ) of the achieved system was 0.32 mg/L for Cr, which is well below the allowed standard limitation for landfills in Sweden. This work shows that XRF can gain enough sensitivity for direct monitoring to certify that the Cr content in leachate is below environmental limits.
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15.
  • Arapitsas, Panagiotis, et al. (författare)
  • Pressurized solvent extraction and monolithic column-HPLC/DAD analysis of anthocyanins in red cabbage
  • 2008
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 74:5, s. 1218-1223
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this work was to develop a fast method for extraction and analysis of anthocyanins in red cabbage. Pressurized hot water containing 5% of ethanol was used as an extremely efficient extraction solvent. HPLC/DAD with a monolithic column was used to accomplish a fast analysis-24 anthocyanin peaks within 18 min. Statistical design was used to optimize the studied extraction parameters: temperature (80-120 degrees C); sample amount (1-3 g); extraction time (6-11 min); concentration of formic acid in the extraction solvent (0-5 vol.%). The best extraction conditions for a majority of the anthocyanin peaks were 2.5 g of sample, 99 degrees C (at 50 bar), 7 min of extraction and a solvent composition of water/ethanol/formic acid (94/5/1, v/v/v).
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16.
  • Araujo, Pedro, et al. (författare)
  • A novel strategy for discriminating marine oils by using the positional distribution (sn-1, sn-2, sn-3) of omega-3 polyunsaturated fatty acids in triacylglycerols
  • 2018
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 182, s. 32-37
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel strategy for discriminating genuine and adulterated marine oils is proposed. The strategy consists of i) determining the stereospecific distribution (sn-1, sn-2 and sn-3) of omega 3 polyunsaturated fatty acids (omega-3 PUFA) on the backbone of triacylglycerols by using liquid chromatography tandem mass spectrometry; ii) transforming the qualitative stereospecific information into quantitative data by means of a novel strategy; iii) analyzing the transformed data by principal component analysis. The proposed strategy was tested on pure oils (seal, salmon, cod liver, sandeel, blue whiting, herring), a mixture of blue whiting, herring, sandeel and Norway pout and some intentionally adulterated oils. In addition, some published krill oil data were analyzed to confirm the reliability of the new approach.
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17.
  • Avagyan, Rozanna, et al. (författare)
  • Target and suspect screening of OH-PAHs in air particulates using liquid chromatography-orbitrap high resolution mass spectrometry
  • 2017
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 165, s. 702-708
  • Tidskriftsartikel (refereegranskat)abstract
    • Up until now, the methods used for determination of hydroxylated polycyclic aromatic hydrocarbons in air particulate samples have been target methods, only determining compounds with available reference standards. In this present study, a combined target and suspect screening strategy for the analysis of hydroxylated polycyclic aromatic hydrocarbons was developed, utilizing liquid chromatography coupled to orbitrap high resolution mass spectrometry. The target screening included simultaneous determination of nine hydroxylated polycyclic aromatic hydrocarbons, while additional eight hydroxylated polycyclic aromatic hydrocarbon masses were screened for using the suspect screening. The target screening was validated with respect to linearity, limits of detection and quantification and matrix effects. The calibration curves ranged from 0.01 to 10 ng/mL, the method limits of detection and. quantification were in the rage of 0.001-0.018 pg/m(3) and 0.006-0.061 pg/m(3), respectively, while matrix effects ranged from 83% to 104%. For the suspect screening, a list with expected precursor ions created from suspect monoisotopic masses was used. The suspects were then identified by the accurate exact mass, with a mass accuracy threshold < 5 ppm, molecular formula, isotopic pattern, and mass spectra (fragments) and also semi-quantified in order to obtain information on their relative levels in different matrixes. The developed strategy was applied on five air particulate samples collected from an urban background and five samples from a car tunnel in Stockholm (Sweden). In total 20 hydroxylated polycyclic aromatic hydrocarbons were detected, of which nine compounds were determined using the target screening and 11 were tentatively identified and semi-quantified using the suspect screening strategy. The concentrations of the target compounds ranged from 20.7 to 96.9 pg/m(3), for most of the analytes the concentrations in particles from car tunnel were slightly higher than in urban air particles. The levels of most of the tentatively identified compounds were also slightly higher in particles from the car tunnel.
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18.
  • Berduque, Alfonso, et al. (författare)
  • Voltammetric characterisation of silicon-based microelectrode arrays and their application to mercury-free stripping voltammetry of copper ions
  • 2007
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 71:3, s. 1022-1030
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper describes the electrochemical characterisation of a range of gold and platinum microelectrode arrays (MEAs) fabricated by standardphotolithographic methods. The inter-electrode spacing, geometry, numbers and dimensions of the electrodes in the arrays were found to influencethe voltammetric behaviours obtained. Excellent correlation was found between experimental data and theoretical predictions employing publishedmodels of microelectrode behaviour. Gold MEAs were evaluated for their applicability to copper determination in a soil extract sample, whereagreement was found between the standard analytical method and a method based on underpotential deposition—anodic stripping voltammetry(UPD-ASV) at the MEAs, offering a mercury-free alternative for copper sensing.
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19.
  • Berlin, Emmanuel, et al. (författare)
  • Lipid organization and turnover in the plasma membrane of human differentiating neural progenitor cells revealed by time-of-flight secondary ion mass spectrometry imaging
  • 2024
  • Ingår i: TALANTA. - 0039-9140 .- 1873-3573. ; 272
  • Tidskriftsartikel (refereegranskat)abstract
    • Membrane lipids have been known to influence multiple signalling and cellular processes. Dysregulation of lipids at the neuronal membrane is connected to a significant alteration of the brain function and morphology, leading to brain diseases and neurodegeneration. Understanding the lipid composition and turnover of neuronal membrane will provide a significant insight into the molecular events underlying the regulatory effects of these biomolecules in a neuronal system. In this study, we aimed to characterize the composition and turnover of the plasma membrane lipids in human neural progenitor cells (NPCs) at an early differentiation stage into midbrain neurons using ToF-SIMS imaging. Lipid composition of the native plasma membrane was explored, followed by an examination of the lipid turnover using different isotopically labelled lipid precursors, including 13C-choline, 13C-lauric acid, 15N-linoleic, and 13C-stearic. Our results showed that differentiating NPCs contain a high abundance of ceramides, glycerophosphoserines, neutral glycosphingolipids, diradylglycerols, and glycerophosphocholines at the plasma membrane. In addition, different precursors were found to incorporate into different membrane lipids which are specific for the short- or long -carbon chains, and the unsaturation or saturation stage of the precursors. The lipid structure of neuronal membrane reflects the differentiation status of NPCs, and it can be altered significantly using a particular lipid precursor. Our study illustrates a potential of ToF-SIMS imaging to study native plasma membrane lipids and elucidate complex cellular processes by providing molecular -rich information at a cell level.
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20.
  • Bhand, Sunil, et al. (författare)
  • Immuno-arrays for multianalyte analysis of chlorotriazines
  • 2005
  • Ingår i: Talanta. - : Elsevier BV. - 1873-3573 .- 0039-9140. ; 65:2, s. 331-336
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, a novel strategy for multicomponent analysis of two classes of pesticides such as triazines (atrazine and simazine) and phenoxyalkanoic acids (2,4-dichlorophenoxy acetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 4-chlorophenoxyacetic acid (CPOAc), phenoxyacetic acid (POAc)) employing immuno-arrays is demonstrated. The approach is based on cross-reactive arrays of specific antibody pairs coupled to chemometric pattern recognition. The monoclonal antibody pairs employed in this work (atrazine–simazine and 2,4-D) are specific towards a set of analytes and preclude a particular set of others present in the sample matrix. Antibody pairs of atrazine, simazine, and 2,4-D are used to discriminate and quantify analyte of interest. Atrazine was quantified in presence of trace concentration of simazine and that of 2,4-D. The combinatorial cross-reactivity of antibody pairs towards simazine, atrazine and 2,4-D is used to distinguish among different classes of analytes and their influence on the signal suppression in immuno-techniques. These sensors exclude recognition by carbamates such as carbaryl and carbofuran.
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21.
  • Bianchi, F., et al. (författare)
  • Differentiation of the volatile profile of microbiologically contaminated canned tomatoes by dynamic headspace extraction followed by gas chromatography-mass spectrometry analysis
  • 2009
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 77:3, s. 962-970
  • Tidskriftsartikel (refereegranskat)abstract
    • The aromatic profile of microbiologically contaminated canned tomatoes was analyzed by the dynamic headspace extraction technique coupled with gas chromatography-mass spectrometry. Canned tomatoes contaminated with Escherichia coli, Saccharomyces cerevisiae and Aspergillus carbonarius were analyzed after 2 and 7 days. About 100 volatiles were detected, among which alcohols, aldehydes and ketones were the most abundant compounds. Gas chromatographic peak areas were used for statistical purposes. First, principal component analysis was carried out in order to visualize data trends and clusters. Then, linear discriminant analysis was performed in order to detect the set of volatile compounds ables to differentiate groups of analyzed samples. Five volatile compounds, i.e. ethanol, beta-myrcene,o-methyl styrene, 6-methyl-5-hepten-2-ol and 1-octanol, were found to be able to better discriminate between uncontaminated and contaminated samples. Prediction ability of the calculated model was estimated to be 100% by the "leave-one-out" cross-validation. An electronic nose device was then used to analyze the same contaminated and not contaminated canned tomato samples. Preliminary results were compared with those obtained by dynamic headspace gas chromatography-mass spectrometry, showing a good agreement.
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22.
  • Bianchi, F., et al. (författare)
  • Novel sample-substrates for the determination of new psychoactive substances in oral fluid by desorption electrospray ionization-high resolution mass spectrometry
  • 2019
  • Ingår i: Talanta. - : Elsevier B.V.. - 0039-9140 .- 1873-3573. ; 202, s. 136-144
  • Tidskriftsartikel (refereegranskat)abstract
    • A reliable screening and non invasive method based on the use of microextraction by packed sorbent coupled with desorption electrospray ionization-high resolution mass spectrometry was developed and validated for the detection of new psychoactive substances in oral fluid. The role of different sample substrates in enhancing signal intensity and stability was evaluated by testing the performances of two polylactide-based materials, i.e. non-functionalized and functionalized with carbon nanoparticles, and a silica-based material compared to commercially available polytetrafluorethylene supports. The best results were achieved by using the non-functionalized polylactide substrates to efficiently ionize compounds in positive ionization mode, whereas the silica coating proved to be the best choice for operating in negative ionization mode. LLOQs in the low μg/L, a good precision with CV% always lower than 16% and RR% in the 83(±4)-120(±2)% range, proved the suitability of the developed method for the determination of the analytes in oral fluid. Finally, the method was applied for screening oral fluid samples for the presence of psychoactive substances during private parties, revealing mephedrone in only one sample out of 40 submitted to analysis.
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23.
  • Bizkarguenaga, Ekhine, et al. (författare)
  • Enrichment of perfluorinated alkyl substances on polyethersulfone using 1-methylpyperidine as ion-pair reagent for the clean-up of carrot and amended soil extracts
  • 2015
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 143, s. 263-270
  • Tidskriftsartikel (refereegranskat)abstract
    • The development of a simple, cheap and environment friendly analytical method for the simultaneous determination of different perfluoroalkyl substances (PFASs) including seven perfluoroalkyl carboxylic acids, three perfluoroalkane sulfonic acids and perfluorooctanesulfonamide in carrot and amended soil was carried out in the present work. The method was based on focused ultrasound solid-liquid extraction followed by extract clean-up through enrichment of the target compounds on a polymeric material using an ion-pair reagent and detection by liquid chromatography-tandem mass spectrometry. The following variables affecting the clean-up step were evaluated: the nature of the polymeric material (polyethersulfone, PES, versus silicone rod), the amount of the polymeric material (from 1 to 9 mg), the ion-pair reagent (1-methylpyperidine, 1-MP, versus tetrabutylammonium salts), the concentration of the ion-pair reagent (from 5 to 50 mM) and the extraction time (from 15 min to 24 h). Optimum clean-up conditions were obtained using preconcentration on 9 mg of PES polymeric material combined with 5 mM 1-MP as ion-pair reagent for 3 h. The method was validated in terms of apparent recoveries in the range of 77-140% and 95-137% at the low concentration (50 ng g(-1)) and in the range of 70-136% and 79-132% at the high concentration (290 ng g(-1)) for amended soil and carrot, respectively, after correction with the corresponding labeled standards. Precision, as relative standard deviation, was within 2-23%, while method detection limits were 0.31-2.85 ng g(-1) for amended soil and 0.11-1.83 ng g(-1) for carrot. In the absence of a certified reference material for the target analytes in the matrices studied, inter-method comparison was carried out and the same samples were processed using two independent clean-up procedures, the one developed in the present work and a classical based on solid-phase extraction. Statistically comparable results were obtained according to the one-way analysis of variance for peel, core, leaves as well as amended soil (F-Calc= 2.59, 5.06, 5.82 and 2.34 < F-Crit= 7.71). Finally, the method was applied for the determination of PFASs in uptake experiments where carrots were cultivated in an amended soil polluted with perfluorooctane sulfonic acid (PFOS) at 500 ng g(-1) level. The highest concentration was measured in the carrot leaves (669 ng g(-1)), while the concentrations in peel and core were at the same level (72 ng g(-1) and 62 ng g(-1) respectively), concluding that translocation of PFOS from the soil to the leaves had occurred.
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24.
  • Bjorklund, Robert, et al. (författare)
  • Electrode specific information from voltammetric monitoring of biogas production
  • 2010
  • Ingår i: Talanta. - : Elsevier Science B.V., Amsterdam.. - 0039-9140 .- 1873-3573. ; 81:04-May, s. 1578-1584
  • Tidskriftsartikel (refereegranskat)abstract
    • A sensor employing pulse voltammetry monitored the liquid phase of a biogas reactor during 32 days of gas production An electrode allay consisting of stainless steel, platinum and rhodium electrodes generated current responses for a sequence of voltage pulses Plots of individual current responses against time indicated the electrochemical changes occurring in the broth from the perspective of each electrode. The responses from stainless steel had a pronounced diurnal oscillation which followed the daily introduction and consumption of substrate The current responses for platinum were in a narrow range whereas those for rhodium exhibited several minima A disturbance in the reactor caused by omission of substrate led to decreases in both gas production and current responses for all the electrodes Multivariate data evaluation of all the current responses by principal component analysis indicated the daily fluctuations for concentrations of ions and redox active compounds in the broth
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25.
  • Carlsson, Jenny, 1977-, et al. (författare)
  • Detection of global glycosylation changes of serum proteins in type 1 diabetes using a lectin panel and multivariate data analysis
  • 2008
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 76:2, s. 333-337
  • Tidskriftsartikel (refereegranskat)abstract
    • Global glycosylation changes of serum proteins in type 1 diabetic patients have in this paper been investigated based on the interaction of the saccharide moiety of serum proteins with different lectins. Lectins are proteins, which bind carbohydrates specifically and reversibly. Panels with lectins of various carbohydrate specificities were immobilized on gold surfaces. Sera from healthy individuals, newly diagnosed type 1 diabetes patients and type 1 diabetes patients having had the disease for 4–6 years, respectively, were applied to the lectin panel. The biorecognition was evaluated with null ellipsometry. Data obtained were related to an internal standard of lactoferrin. Multivariate data analysis (MVDA) techniques were used to analyze data. Principal component analysis showed that the lectin panel enabled discrimination between sera from the three different above-mentioned groups. Using an artificial neuronal net (ANN), it was possible to correctly categorize unknown serum samples into one of the three groups.  
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26.
  • Crespi, Miguel Coll, et al. (författare)
  • Agarose hydrogel containing immobilized pH buffer microemulsion without increasing permselectivity
  • 2018
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 177, s. 191-196
  • Tidskriftsartikel (refereegranskat)abstract
    • A heterogeneous pH buffer based on a colloidal emulsion containing ion-exchanger and lipophilic base is described that can be integrated into hydrogels without affecting their ion-exchange properties. Each sphere works on the basis of reversible ion-exchange of hydrogen ions with solution cations, acting as a pH buffer while staying removed from solution in the nonpolar core of the spheres. The ion-exchange mechanism is supported by titration experiments in aqueous emulsion, showing that the nature and concentration of the exchanging solution cations influences the buffer action, with increasing lipophilicity moving the equilibrium to lower pH values. Agarose gels with entrapped pH buffer emulsions and mounted in a transport cell are shown by zero current potentiometry to exhibit negligible permselective properties above an ionic strength of 1 mM, a behavior no different from unmodified agarose, with an observed ion-exchanger concentration of 7 mM in dry agarose. This suggests that such pH buffers do not give rise to substantial ion-exchange properties of the gel material. In a first attempt to control the pH in the vicinity of an electrode surface by this approach, the emulsion was entrapped in an agarose gel in direct contact with a pH electrode, demonstrating the ability to buffer such gel films.
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27.
  • De Brabandere, Heidi, et al. (författare)
  • Sediment extraction and clean-up for organic phosphorus analysis by electrospray ionization tandem mass spectrometry
  • 2008
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 74:5, s. 1175-1183
  • Tidskriftsartikel (refereegranskat)abstract
    • A method to prepare NaOH sediment extracts for organic P compound analysis with electrospray ionization tandem mass spectrometry (ESI-MS-MS) was developed on natural samples. Ion exchange, rotary evaporation and mass cut-off filtering proved to be suitable for sample preparation. Samples were analyzed with ESI-MS-MS, and reproducibility and repeatability of the method was calculated. In addition, 31P-nuclear magnetic resonance spectroscopy (31P NMR) was used to measure recovery of different P compound groups such as orthophosphate (Ortho-P), orthophosphate monoesters (Monoester-P), orthophosphate diesters (Diester-P) and pyrophosphates (Pyro-P). The developed sample preparation method resulted in an easy-to-spray liquid for the ESI-MS-MS instrumentation. The overall P recovery was 65% and 31P NMR showed that Diester-P, possibly in the form of DNA, was apparently lost through the filtering step most likely due to their size. Variances in the total intensities of the MS scans (relative standard deviation (R.S.D.) 35–54%) were for about 50% due to repeated MS runs. Covariances of the peaks in the MS spectra were calculated to be for about 30% due to the sample preparation procedure. Finally, with the ESI-MS-MS approach, 11 peaks in the mass spectra were found likely to represent phosphate containing compounds.
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28.
  • Degueldre, C., et al. (författare)
  • Uranium colloid analysis by single particle inductively coupled plasma-mass spectrometry
  • 2006
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 68:3, s. 623-628
  • Tidskriftsartikel (refereegranskat)abstract
    • Uranium single particle analysis has been performed by inductively coupled plasma-mass spectrometry (ICP-MS) and the performances are compared with that provided by scanning electron microsopy and single particle counting. The transient signal induced by the flash of ions due to the ionisation of all titanium Colloidal particle in the plasma torch can be detected and measured for selected uranium ion masses (U-238(+), U-235(+) or 254[(UO)-U-238-O-16](+)) by the mass spectrometer. The signals recorded via time scanning are analysed as a function of particle size or fraction of the studied element or isotope in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. The feasibility tests were performed on uranium dioxide particles. The study also describes the experimental conditions and the choice of mass to detect uranium colloids in a single particle analysis mode.
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29.
  • Dock, Eva, et al. (författare)
  • Multivariate data analysis of dynamic amperometric biosensor responses from binary analyte mixtures - application of sensitivity correction algorithms
  • 2005
  • Ingår i: Talanta. - : Elsevier BV. - 1873-3573 .- 0039-9140. ; 65:2, s. 298-305
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, it is demonstrated that a single-receptor biosensor can be used to quantitatively determine each analyte in binary Mixtures LIS in multivariate data analysis tools based on the dynamic responses received from flow injection peaks. Mixtures with different concentrations of two phenolic compounds, catechol and 4-chlorophenol, were measured with a graphite electrode modified with tyrosinase enzyme at an applied potential of -50 mV versus Ag/AgCl. A correction algorithm based on measurements of references in-between samples was applied to compensate for biosensor ageing as well as differences caused by deviations between biosensor preparations. After correction, the relative prediction errors with partial least squares regression (PLS-R) for catechol and 4-chlorophenol were 7.4 and 5.5%, respectively, using an analysis sequence measured on one biosensor. Additional validation mixtures of the two phenols were measured with a new biosensor, prepared with the same procedure but with a different batch of tyrosinase enzyme. Using the mixture responses for the first sensor as a calibration set in PLS-R. the relative prediction errors of the validation mixtures, after applying correction procedures. were 7.0% for catechol and 16.0% for 4-chlorophenol. These preliminary results indicate that by applying correction algorithms it could be possible to use less stable biosensors in continuous on-line measurements together with multivariate data analysis without time-consuming calibration procedures. (C) 2004 Elsevier B.V. All rights reserved.
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30.
  • Duarte, H., et al. (författare)
  • Sustainable extraction of polyphenols from vine shoots using deep eutectic solvents : Influence of the solvent, Vitis sp., and extraction technique
  • 2024
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 267
  • Tidskriftsartikel (refereegranskat)abstract
    • Vine shoots are the main by-products of grapevine pruning with no added value. In the present study, deep eutectic solvents (DESs) were used as alternatives to traditional chemical solvents, for the extraction of phytochemicals from grapevine shoots. Three levulinic acid-based DESs were tested for the first time, and their performance was compared to methanol (a standard chemical solvent) regarding the extraction of phenolic compounds from thirteen Vitis sp. shoots. Two extraction methods have been applied: ultrasound-assisted extraction and solid-liquid extraction. A total of eleven polyphenols which belongs to four families (proanthocyanins, stilbenes, hydroxycinnamic acids, and flavonols) have been identified and quantified in the extracts. The statistical analysis shows that the levulinic acid-based DES systems are novel and important alternatives to chemical solvents due to favourable eco-friendly properties and remarkable extraction performance of polyphenols. On the other hand, the ultrasound-assisted extraction technique has significantly increased the extraction rate in comparison to the solid-liquid extraction method with p-values lower than 0.05 for most compounds. The genetic factor has been shown to play an important role in the content of extracted polyphenols, being V. riparia pubescente the one that presented the highest concentrations of extracted polyphenols. Finally, the polyphenol-enriched extracts have proven important properties such as antioxidant activity and significant delay in bacteria growth against both gram-positive and gram-negative bacteria. It is important to note that, to the best of our knowledge, this is the first time that deep eutectic solvents have been used for the extraction of bioactive compounds from vine shoot residues.
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31.
  • Dursun, Ali D., et al. (författare)
  • Surface plasmon resonance aptasensor for Brucella detection in milk
  • 2022
  • Ingår i: Talanta. - Amsterdam, Netherlands : Elsevier. - 0039-9140 .- 1873-3573. ; 239
  • Tidskriftsartikel (refereegranskat)abstract
    • A Surface Plasmon Resonance (SPR) aptasensor was developed for the detection of Brucella melitensis (B. melitensis) in milk samples. Brucellosis is a bacterial zoonotic disease with global distribution caused mostly by contaminated milk or their products. Aptamers recognizing B. melitensis were selected following a whole bacteria-SELEX procedure. Two aptamers were chosen for high affinity and high specificity. The high affinity aptamer (B70 aptamer) was immobilized on the surface of magnetic silica core-shell nanoparticles for initial purification of the target bacteria cells from milk matrix. Another aptamer, highly specific for B. melitensis cells (B46 aptamer), was used to prepare SPR sensor chips for sensitive determination of Brucella in eluted samples from magnetic purification since direct injection of milk samples to SPR sensor chips is known for a high background unspecific signal. Thus, we integrated a quick and efficient magnetic isolation step for subsequent instant detection of B. melitensis contamination in one ml of milk sample by SPR with a LOD value as low as 27 ± 11 cells.
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32.
  • El-Wekil, Mohamed M., et al. (författare)
  • Enzyme-free and label-free strategy for electrochemical oxaliplatin aptasensing by using rGO/MWCNTs loaded with AuPd nanoparticles as signal probes and electro-catalytic enhancers
  • 2020
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 217
  • Tidskriftsartikel (refereegranskat)abstract
    • An innovative label free electrochemical aptasensor was developed for the analysis of oxaliplatin (OXAL) for the first time. The DNA oligonucleotide (aptamer) was successfully fabricated, by covalently attaching the amino terminus of the functional DNA on the glassy carbon electrode (GCE) surface modified with reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) loaded with AuPd nanoparticles (AuPd NPs@rGO/MWCNTs/GCE). The stepwise assembly process of aptasensor on AuPd NPs@rGO/MWCNTs/GCE was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The aptamer-OXAL complex formation led to inhibition the electron transfer of Fe(CN)63−/4- on the electrode interface, which was clearly observed by decreasing the peak current of the redox probe. Furthermore, we managed to quantitatively measure OXAL by adding different concentrations of OXAL, while monitoring the decrease of differential pulse voltammogram (DPV) responses of the redox probe. Under the optimized conditions, the electrochemical aptasensor exhibited a linear range of 0.1–170.0 nmol L−1 with LOD of 60.0 pmol L−1. Next, we successfully applied the aptasensor calibrated system to determine OXAL in pharmaceutical injection and human biological samples.
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33.
  • Farajzadeh, Mir Ali, et al. (författare)
  • Optimization of dispersive liquid-liquid microextraction of copper (II) by atomic absorption spectrometry as its oxinate chelate: Application to determination of copper in different water samples
  • 2008
  • Ingår i: Talanta. - : Elsevier BV. - 1873-3573 .- 0039-9140. ; 75:3, s. 832-840
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study a dispersive liquid-liquid microextraction (DLLME) method based on the dispersion of an extraction solvent into aqueous phase in the presence of a dispersive solvent was investigated for the preconcentration of Cu2+ ions. 8-Hydroxy quinoline was used as a chelating agent prior to extraction. Flame atomic absorption spectrometry using an acetylene-air flame was used for quantitation of the analyte after preconcentration. The effect of various experimental parameters on the extraction was investigated using two optimization methods, one variable at a time and central composite design. The experimental design was performed at five levels of the operating parameters. Nearly the same results for optimization were obtained using both methods: sample size 5 mL; volume of dispersive solvent 1.5 mL; dispersive solvent methanol; extracting solvent chloroform; extracting solvent volume 250 mu L; 8-hydroxy quinoline concentration and salt amount do not affect significantly the extraction. Under the optimum conditions the calibration graph was linear over the range 50-2000 mu g L-1. The relative standard deviation was 5.1% for six repeated determinations at a concentration of 500 mu g L-1. The limit of detection (S/N = 3) was 3 mu g L-1.
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34.
  • Geladi, Paul (författare)
  • Influence of grain topography on near infrared hyperspectral images
  • 2012
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 89, s. 223-230
  • Tidskriftsartikel (refereegranskat)abstract
    • Near infrared hyperspectral imaging (NIR-HSI) allows spatially resolved spectral information to be collected without sample destruction. Although NIR-HSI is suitable for a broad range of samples, sizes and shapes, topography of a sample affects the quality of near infrared (NIR) measurements. Single whole kernels of three cereals (barley, wheat and sorghum), with varying topographic complexity, were examined using NIR-HSI. The influence of topography (sample shape and texture) on spectral variation was examined using principal component analysis (PCA) and classification gradients. The greatest source of variation for all three grain types, despite spectral preprocessing with standard normal variate (SNV) transformation, was kernel curvature. Only 1.29% (PC5), 0.59% (PC6) and 1.36% (PC5) of the spectral variation within the respective barley, wheat and sorghum image datasets was explained within the principal component (PC) associated with the chemical change of interest (loss of kernel viability). The prior PCs explained an accumulated total of 91.18%, 89.43% and 84.39% of spectral variance, and all were influenced by kernel topography. Variation in sample shape and texture relative to the chemical change of interest is an important consideration prior to the analysis of NIR-HSI data for non-flat objects. (C) 2011 Elsevier B.V. All rights reserved.
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35.
  • Geng, Dawei, 1986-, et al. (författare)
  • Analysis of brominated flame retardants and their derivatives by atmospheric pressure chemical ionization using gas chromatography coupled to tandem quadrupole mass spectrometry
  • 2017
  • Ingår i: Talanta. - Amsterdam, Netherlands : Elsevier. - 0039-9140 .- 1873-3573. ; 162, s. 618-624
  • Tidskriftsartikel (refereegranskat)abstract
    • A validated method using an atmospheric pressure chemical ionization source for coupling gas chromatography (GC-APCI) to tandem quadrupole mass spectrometry (MS/MS) for the determination of brominated flame retardants (BFRs) is presented. Polybrominated diphenyl ethers (PBDEs), their methoxylated derivatives (MeO-PBDEs) and other emerging BFRs were included in this study. The method showed good linearity and repeatability. The relative standard deviation (RSD) of the relative response factors (RRFs) of all compounds was less than 16%. Repeatability for BFRs was tested on one or two concentration levels of calibration standardswith RSDs for RRFs below 16%. The lowest calibration standards (0.075 –0.1 pg/μL for emerging BFRs, BDE 209 and MeO-PBDEs mixtures, 0.625 –6.25 pg/μL for Br1-9 PBDEs mixtures) were used as instrument detection limits (IDL). The method was applied on biotic samples, including fish, osprey, and seal. In general, BDE209 and decabromodiphenyl ethane (DBDPE) were detected in 50% of the seal samples. A 100% detection rate was achieved for 6-MeO-BDE47 in all the samples (72 –580 pg/g ww in osprey samples, 24 000 –96 000 pg/g ww in seal samples and 78–99 pg/g ww in fish samples). AllBr3-6PBDEs (BDE28, 47, 99, 100, 153, 154) were detected in all the samples (ranging from 12 to 20 000 pg/g ww), while BDE183 was detected in 60% of the osprey eggs, 20% of the seal samples and below MDL in all fish samples. The results presented indicate the capability of the GC-APCI-MS/MS system for the detection and quantification of BFRs.
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36.
  • Ghasemi, J., et al. (författare)
  • A new algorithm for the determination of protolytic constants from spectrophotometric data in multiwavelength mode : Calculations of acidity constants of 4-(2-pyridylazo)resorcinol (PAR) in mixed nonaqueous-water solvents
  • 2006
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 68:4, s. 1201-1214
  • Tidskriftsartikel (refereegranskat)abstract
    • A new efficient, simple and versatile algorithm is presented for determination of the protolytic constants from spectrophotmetric data in multiwavelength mode based on the combining of hard and soft modeling. The algorithm was checked by determining the acidity constants of a triprotic acid from theoretical and real absorption-pH data. The real spectral data are obtained from photometric titration of different solutions of 4-(2-pyridylazo)resorcinol (PAR) by a standard base solution under an inert atmosphere. The algorithm starts the minimization process using an user supplied number of components and initial guesses of the unknown parameters and refined in a least squares manner. New algorithm is implemented in the new version of DATAN package (version 3.1). The validity of the obtained results was checked by some well known programs such as DATAN 2.1, SPECFIT/32, SQUAD, a modified version of difference spectra and a A-pH curve method. The comparison of the outputs of the DATAN 3.1 with the other programs reveals that there is a very good agreement between the obtained results and mentioned programs.
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37.
  • Ghorbanzad‘e, Mehdi, et al. (författare)
  • Quantitative and qualitative prediction of corneal permeability for drug-like compounds
  • 2011
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 85:5, s. 2686-2694
  • Tidskriftsartikel (refereegranskat)abstract
    • A set of 69 drug-like compounds with corneal permeability was studied using quantitative and qualitative modeling techniques. Multiple linear regression (MLR) and multilayer perceptron neural network (MLP-NN) were used to develop quantitative relationships between the corneal permeability and seven molecular descriptors selected by stepwise MLR and sensitivity analysis methods. In order to evaluate the models, a leave many out cross-validation test was performed, which produced the statistic Q2 = 0.584 and SPRESS = 0.378 for MLR and Q2 = 0.774 and SPRESS = 0.087 for MLP-NN. The obtained results revealed the suitability of MLP-NN for the prediction of corneal permeability. The contribution of each descriptor to MLP-NN model was evaluated. It indicated the importance of the molecular volume and weight. The pattern recognition methods principal component analysis (PCA) and hierarchical clustering analysis (HCA) have been employed in order to investigate the possible qualitative relationships between the molecular descriptors and the corneal permeability. The PCA and HCA results showed that, the data set contains two groups. Then, the same descriptors used in quantitative modeling were considered as inputs of counter propagation neural network (CPNN) to classify the compounds into low permeable (LP) and very low permeable (VLP) categories in supervised manner. The overall classification non error rate was 95.7% and 95.4% for the training and prediction test sets, respectively. The results revealed the ability of CPNN to correctly recognize the compounds belonging to the categories. The proposed models can be successfully used to predict the corneal permeability values and to classify the compounds into LP and VLP ones. Highlights ► Linear and nonlinear prediction of corneal permeability using molecular descriptors. ► MLP-NN model was found to be more successful than MLR equation. ► Molecular volume and molecular weight were identified as the most important descriptors. ► Categorizing drugs in two low permeable and very low permeable compounds groups. ► CPNN model can correctly recognize objects belonging to the groups.
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38.
  • Golovko, Oksana, et al. (författare)
  • New extraction method prior to screening of organic micropollutants in various biota matrices using liquid chromatography coupled to high-resolution time-of-flight mass spectrometry
  • 2020
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 219
  • Tidskriftsartikel (refereegranskat)abstract
    • A new extraction method with limited clean-up requirements prior to screening various matrices for organic micropollutants using liquid chromatography-high resolution mass spectrometry (LC-HRMS) for analysis was developed. First, the performance of three extraction methods (QuEChERS with SPE clean-up, ultrasonication with SPE clean-up, extraction without SPE clean-up) was tested, optimized, and compared using > 200 contaminants of emerging concern (CECs) together covering a wide range of physicochemical properties applicable for suspect and non-target screening in biota. White-tailed sea eagle (Haliaeetus albicilla) muscle tissue was used in method development and optimization. The method without SPE clean-up was then applied to European perch (Perca fluviatilis) muscle, heart, and liver tissues. The optimization and application of the method demonstrated a wide applicable domain of the novel extraction method regarding species, tissues, and chemicals. For future applications, the suitability of the method for suspect and non-target screening was tested. Overall, our extraction method appears to be sufficiently simple and broad (relatively non-discriminant) for use prior to analysis of CECs in various biota.
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39.
  • Grabic, Roman, et al. (författare)
  • Multi-residue method for trace level determination of pharmaceuticals in environmental samples using liquid chromatography coupled to triple quadrupole mass spectrometry
  • 2012
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 100, s. 183-195
  • Tidskriftsartikel (refereegranskat)abstract
    • A multi-residue method for the simultaneous determination of more than 90 pharmaceuticals in water samples was developed and validated. The developed method utilizes a single liquid chromatography–tandem mass spectrometry (LC–MS/MS) run after sample enrichment using solid-phase extraction (SPE). The pharmaceuticals included in this method were chosen based on their potency (effect/concentration ratio) and potential to bioaccumulate in fish. Because the selection was based on ecotoxicological criteria and not on ease of detection, the pharmaceuticals have a wide range of physico-chemical properties and represent twenty-seven distinct classes. No method for surface, waste water or similar matrices was previously described for 52 of the 100 target analytes. Four chromatographic columns were tested to optimize the separation prior to detection by mass spectrometry (MS). The resulting method utilizes a Hypersil Gold aQ column. Three different water matrices were tested during method validation: Milli-Q water, surface water (river water from the Umea River) and effluent from the Umea waste water treatment plant (WWTP). Four of the selected pharmaceuticals exhibited poor method efficiency in all matrices. Amiodarone, Dihydroergotamine, Perphenazine and Terbutalin were omitted from the final analytical method (). In addition, five compounds were excluded from the method for surface water (Atorvastatin, Chloropromazin, Dipyridamol, Furosemid and Ranitidin) and three other pharmaceuticals (Glibenclamid, Glimepirid and Meclozine) from waste water method respectively. Absolute recoveries were above 70% for Milli-Q water, surface water, and sewage effluent for most pharmaceuticals. The limits of quantification (LOQs) ranged from 0.05 to 50 ng L−1 (median 5 ng L−1). The use of matrix-matched standards led to the elimination of ionization enhancement or suppression. The recoveries of the method for real matrices were in the range of 23% to 134% for surface water (only three compounds were outside of the range of 40–130%) and in the range of 47% to 162% for waste water (five compounds were outside of the range of 40–130% at lower validated concentration).
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40.
  • Haberska, Karolina, et al. (författare)
  • Activity of lactoperoxidase when adsorbed on protein layers
  • 2008
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 76:5, s. 1159-1164
  • Tidskriftsartikel (refereegranskat)abstract
    • Lactoperoxidase (LPO) is an enzyme, which is used as an antimicrobial agent in a number of applications, e.g., food technology. In the majority of applications LPO is added to a homogeneous product phase or immobilised on product surface. In the latter case, however, the measurements of LPO activity are seldom reported. In this paper we have assessed LPO enzymatic activity on bare and protein modified gold surfaces by means of electrochemistry. It was found that LPO rapidly adsorbs to bare gold surfaces resulting in an amount of LPO adsorbed of 2.9 mg/m2. A lower amount of adsorbed LPO is obtained if the gold surface is exposed to bovine serum albumin, bovine or human mucin prior to LPO adsorption. The enzymatic activity of the adsorbed enzyme is in general preserved at the experimental conditions and varies only moderately when comparing bare gold and gold surface pretreated with the selected proteins. The measurement of LPO specific activity, however, indicate that it is about 1.5 times higher if LPO is adsorbed on gold surfaces containing a small amount of preadsorbed mucin in comparison to the LPO directly adsorbed on bare gold.
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41.
  • Haghighi, Behzad, et al. (författare)
  • Prussian blue modified glassy carbon electrodes - Study on operational stability and its application as a sucrose biosensor
  • 2004
  • Ingår i: Talanta. - : Elsevier BV. - 1873-3573 .- 0039-9140. ; 64:1, s. 3-12
  • Tidskriftsartikel (refereegranskat)abstract
    • Stabilisation of electrochemically deposited Prussian blue (PB) films on glassy carbon (GC) electrodes has been investigated and an enhancement in the stability of the PB films is reported if the electrodes are treated with tetrabutyl ammonium toluene-4-sulfonate (TTS) in the electrochemical activation step following the electrodeposition. A multi-enzyme PB based biosensor for sucrose detection was made in order to demonstrate that PB films can be coupled with an oxidase system. A tri-enzyme system, comprising glucose oxidase, mutarotase and invertase, was crosslinked with glutaraldehyde and bovine albumin serum on the PB modified glassy carbon electrode. The deposited PB operated as an electrocatalyst for electrochemical reduction of hydrogen peroxide, the final product of the enzyme reaction sequence. The electrochemical response was studied using flow injection analysis for the determination of sucrose, glucose and H2O2. The optimal concentrations of the immobilisation mixture was standardised as 8 U of glucose oxidase, 8 U of mutarotase, 16 U of invertase, 0.5% glutaraldchyde (0.025 mul) and 0.5 % BSA (0.025 mg) in a final volume of 5 mul applied at the electrode surface (0.066 cm(2)). The biosensor exhibited a linear response for sucrose (4-800 muM), glucose (2-800 muM) and H2O2 (1-800 muM) and the detection limit was 4.5, 1.5 and 0.5 muM for sucrose, glucose and H2O2, respectively. The sample throughput was ca. 60 samples h(-1). An increase in the operational and storage stability of the sucrose biosensor was also noted when the PB modified electrodes were conditioned in phosphate buffer containing 0.05 M TTS during the preparation of the PB films. (C) 2004 Elsevier B.V. All rights reserved.
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42.
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43.
  • Hansson, Helena, 1968-, et al. (författare)
  • Assessment of a dynamic hollow-fibre liquid phase microextraction system forhuman blood plasma samples
  • 2009
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 77:4, s. 1309-1314
  • Tidskriftsartikel (refereegranskat)abstract
    • A dynamic liquid phase microextraction (LPME) system, based on hollow-fibre supported liquid membrane(SLM) extraction, was developed for extracting ionisable xenobiotics from human plasma, andits performance was evaluated (in terms of extraction efficiency, reproducibility, durability and carryover)using nitrophenolic compounds as model analytes at concentrations of 0.1–0.5gmL−1 in aqueousstandards. The efficiency and repeatability were tested also on spiked human plasma. The system isnon-expensive, convenient, requires minimal manual handling and enables samples with volumes assmall as 0.2mL to be extracted. For plasma samples extraction efficiencies of between 30 and 58% wereachieved within 20 min, including washing steps. The limit of detection (LOD) values were in the range0.02–0.03gmL−1. The developed system can provide enrichment factors up to eight, based on theinjection-to-acceptor volume ratio (in this case 0.2–0.025 mL). The same hollow-fibre membrane wasused up to 8 days with no loss of efficiency. Carry-over was lower than detection limit.
  •  
44.
  • Hansson, Helena, et al. (författare)
  • Dynamic hollow-fibre liquid phase microextraction of dinitrophenols from human plasma: Optimization of an extraction flow system using experimental design methodology
  • 2009
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 79:3, s. 633-638
  • Tidskriftsartikel (refereegranskat)abstract
    • The utility of a dynamic hollow-fibre liquid phase microextraction method (optimized using a four-variable experimental design and response surface modelling) for extracting dinitrophenolic compounds from human plasma samples was evaluated. The investigated variables were donor phase salt concentration (10–400 mM), donor phase pH (2–6), acceptor phase pH (7–12), and donor/acceptor phase flow rates (30/7.5 to 70/17.5 μL min−1). Four dinitrophenol pesticides were used as model substances at concentrations of 0.1 μg mL−1 in spiked human plasma samples. Extraction efficiencies ranging from 42 to 77% with RSDs below 9 were achieved with the optimized method. The flow rate and acceptor pH were shown to strongly affect the extraction efficiency for all compounds, while the donor phase pH and salt concentration had minor effects. With a well-defined acceptor phase pH and flow rate the system exhibited high robustness. The limits of quantification for the investigated compounds, using the presented extraction method followed by liquid chromatography/electrospray ionization mass spectrometry in selected ion monitoring mode, ranged from 0.05 to 0.1 μg mL−1 plasma.
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45.
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46.
  • Huynh, Khoa, et al. (författare)
  • Quantification of total concentration of thiol functional groups in environmental samples by titration with monobromo(trimethylammonio) bimane and determination with tandem mass spectrometry
  • 2020
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 218
  • Tidskriftsartikel (refereegranskat)abstract
    • Thiol compounds (R–SH) have many important biological functions and are principal controls of the speciation of several toxic metals in the environment. However, determining the concentration of thiols associated with environmental matrices is challenging due to the compounds’ low abundance and interferences from non-thiol compounds for many available methods. Here a novel method has been developed and validated to quantify the total concentration of thiol functional groups in aqueous samples using derivatization with monobromo(trimethylammonio)bimane (qBBr) and quantification with tandem mass spectrometry. The thiol concentration was determined by titration of the sample with qBBr, which reacts selectively with thiols, and quantification of the residual qBBr. We systematically evaluated potential interferences from various organic compounds, inorganic ions (including sea water matrices), sulfide and mercury (Hg) species, and demonstrate that the method is highly sensitive, selective and robust. The limit of detection (LOD) for total thiols is in the nanomolar concentration range (~6 nM). The method performance was also demonstrated by determination of the total thiol concentration in different natural samples including boreal stream water (1.16 μM), wetland porewater (0.96 μM) and the Suwanee River natural organic matter (NOM) reference material SR101 N (7.9 μmol g−1). The developed method represents a combination of low LOD and high selectivity and robustness that is unsurpassed for total thiol concentration measurements.
  •  
47.
  • Hyder, Murtaza, et al. (författare)
  • Determination of polycyclic aromatic hydrocarbons (PAHs) from organic aerosols using hollow fiber micro - porous membrane liquid - liquid extraction (HF-MMLLE) followed by gas chromatography-mass spectrometry analysis.
  • 2011
  • Ingår i: Talanta. - : Elsevier BV. - 1873-3573 .- 0039-9140. ; 85:2, s. 919-926
  • Tidskriftsartikel (refereegranskat)abstract
    • A method for determination of polycyclic aromatic hydrocarbons (PAHs) from aerosols was developed. Instead of conventionally used non-polar or slightly polar phenylmethylpolysiloxane column a highly polar, highly substituted, cyanopropyl column (VF-23 MS) was used for separation of PAHs. Based on hollow fiber micro-porous membrane liquid-liquid extraction (HF-MMLLE) a method was developed for sample clean up and pretreatment. An enrichment factor of 617-1022 was obtained with extraction efficiency 10.2-18.9% for different PAHs analyzed in this study. The optimized method was successfully applied to aerosol samples and limits of detection between 1.2pgm(-3) and 180pgm(-3) was obtained. Almost all PAHs were found in most of the aerosol samples.
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48.
  • Höjer Holmgren, Karin, et al. (författare)
  • Part 1 : Tracing Russian VX to its synthetic routes by multivariate statistics of chemical attribution signatures
  • 2018
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 186, s. 586-596
  • Tidskriftsartikel (refereegranskat)abstract
    • Chemical attribution signatures (CAS) associated with different synthetic routes used for the production of Russian VX (VR) were identified. The goal of the study was to retrospectively determine the production method employed for an unknown VR sample. Six different production methods were evaluated, carefully chosen to include established synthetic routes used in the past for large scale production of the agent, routes involving general phosphorus-sulfur chemistry pathways leading to the agent, and routes whose main characteristic is their innate simplicity in execution. Two laboratories worked in parallel and synthesized a total of 37 batches of VR via the six synthetic routes following predefined synthesis protocols. The chemical composition of impurities and byproducts in each route was analyzed by GC/MS-EI and 49 potential CAS were recognized as important markers in distinguishing these routes using Principal Component Analysis (PCA). The 49 potential CAS included expected species based on knowledge of reaction conditions and pathways but also several novel compounds that were fully identified and characterized by a combined analysis that included MS-CI, MS-EI and HR-MS. The CAS profiles of the calibration set were then analyzed using partial least squares discriminant analysis (PLS-DA) and a cross validated model was constructed. The model allowed the correct classification of an external test set without any misclassifications, demonstrating the utility of this methodology for attributing VR samples to a particular production method. This work is part one of a three-part series in this Forensic VSI issue of a Sweden-United States collaborative effort towards the understanding of the CAS of VR in diverse batches and matrices. This part focuses on the CAS in synthesized batches of crude VR and in the following two parts of the series the influence of food matrices on the CAS profiles are investigated.
  •  
49.
  • Höjer Holmgren, Karin, et al. (författare)
  • Synthesis route attribution of sulfur mustard by multivariate data analysis of chemical signatures
  • 2018
  • Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 186, s. 615-621
  • Tidskriftsartikel (refereegranskat)abstract
    • A multivariate model was developed to attribute samples to a synthetic method used in the production of sulfur mustard (HD). Eleven synthetic methods were used to produce 66 samples for model construction. Three chemists working in both participating laboratories took part in the production, with the aim to introduce variability while reducing the influence of laboratory or chemist specific impurities in multivariate analysis. A gas chromatographic/mass spectrometric data set of peak areas for 103 compounds was subjected to orthogonal partial least squares - discriminant analysis to extract chemical attribution signature profiles and to construct multivariate models for classification of samples. For one- and two-step routes, model quality allowed the classification of an external test set (16/16 samples) according to synthesis conditions in the reaction yielding sulfur mustard. Classification of samples according to first-step methodology was considerably more difficult, given the high purity and uniform quality of the intermediate thiodiglycol produced in the study. Model performance in classification of aged samples was also investigated.
  •  
50.
  • Iqbal, Zafar, et al. (författare)
  • Colorimetric analysis of water and sand samples performed on a mobile phone
  • 2011
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 84:4, s. 1118-1123
  • Tidskriftsartikel (refereegranskat)abstract
    • Analysis of water and sand samples was done by reflectance measurements using a mobile phone. The phone’s screen served as light source and front view camera as detector. Reflected intensities for white, red, green and blue colors were used to do principal component analysis for classification of several compounds and their concentrations in the water. Classification of iron (III), chromium (VI) and sodium salt of humic acid was obtained using reflected intensities from blue and green light for concentrations 2-10 mg/l. Analysis of As(III) from 25-400 μg/l based on reflection of red light was performed utilizing the bleaching reaction of tincture of iodine containing starch. Enhanced sensitivity to low concentrations of arsenic was obtained by adding reflected intensities from white light to the analysis. Model colored sand samples representing discoloration caused by the presence of arsenic in groundwater were also analyzed.
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