| 1. |
- Bjarnason, Bjarni, et al.
(författare)
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Enzyme flow immunoassay using a Protein G column for the screening of triazine herbicides in surface and waste water
- 2001
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 426:2, s. 197-207
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Tidskriftsartikel (refereegranskat)abstract
- A method for screening of triazine herbicides in surface and waste water is presented. The method is based on an enzyme flow immunoassay (EFIA) for the detection of the free fraction of a horse radish peroxidase (HRP)-labelled antigen (tracer). This was accomplished by trapping the bound tracer fraction in a Protein G column, allowing the residual free tracer fraction to pass and be detected spectrophotometrically after incubation with an enzyme substrate. As compared with detecting the bound tracer fraction this reduces the regeneration requirements of the Protein G column used for capturing the bound fraction and, therefore, reduces assay time. A polyclonal antibody directed against simazine showed no reactivity towards tracers that were thiopropionic acid derivatives of atrazine, simazine and terbutylazine. It had good sensitivity towards tracers using derivatives of 2-chloro-4,6-(alkylamino)-s-triazines such as atrazine and simazine. The highest sensitivity was obtained with an Et/Cl/N-C5-HRP tracer because this tracer could be used in combination with the lowest concentration of antibody. The detection limit was 0.1 μgl-1 with a linear range between 0.1 and 10 μgl-1 and an assay throughput of 12 h-1. Natural water samples from various locations in Russia were analysed for triazines and the results were compared with a previously developed fluorescein flow immunoassay for triazines. The results were further verified by supported liquid membrane (SLM) extraction combined with HPLC. The results show that the two immunoassays behave differently and that the sample matrix influences their performance, however, no false negative results were obtained. The possible reasons for the different results between the two immunoassays are discussed. (C) 2001 Elsevier Science B.V.
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| 2. |
- Dzgoev, A., et al.
(författare)
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Optimization of a charge coupled device imaging enzyme linked immuno sorbent assay and supports for the simultaneous determination of multiple 2,4-D samples
- 1997
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 347:1-2, s. 87-93
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Tidskriftsartikel (refereegranskat)abstract
- A chemiluminescent microformat enzyme linked immune sorbent assay (ELISA) has been optimized for the simultaneous determination of multiple 2,4-dichlorophenoxyacetic acid (2,4-D) samples. The competitive immunoassay employed a 2,4-D-BSA conjugate, anti-2,4-D monoclonal antibodies and alkaline phosphatase (AP) labelled anti-mouse IgG. The bound AP conjugate was determined by quantitating the chemiluminescence emission from the enzymatic decomposition of the luminogenic substrate, CSPD, by AP using a cooled charge coupled device (CCD) camera. The detection limit for the simultaneous determination of multiple samples was 4.3x10-10 M corresponding to 96 pg ml-1 or 192 fg well with a coefficient of variation (CV, %) of 12.5%. The linear range of the assay was 4.5 x 10-7-4.5 x 10-10 M. The ability of gold coated silicon wafers and glass capillaries to serve as solid phase supports in the imaging ELISA was investigated. The highly reflective gold surfaces improved both the linear range and the sensitivity of the assay, as compared to thick-film patterned surfaces. The capillary supports, on the other hand, lead to a reduction in the linear range and the sensitivity of the assay, as compared to the thick-film patterned surfaces. Initial studies indicate that the capillaries guide the light and may provide a built-in mechanism for collecting the emitted light. Strategies for further development of support materials for imaging-based detectors will be discussed.
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| 3. |
- Gascón, Jordi, et al.
(författare)
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Performance of two immunoassays for the determination of atrazine in sea water samples as compared with on-line solid phase extraction-liquid chromatography-diode array detection
- 1996
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 330:1, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- Two immunoassay formats, magnetic particles-based assay (Atrazine RaPID assay and Atrazine High-Sensitivity RaPID assay) and microtiter plate based assay (Department of Entomology and Environmental Toxicology, University of California in Davis) were evaluated for the determination of atrazine in sea water samples. The results obtained were compared and validated with those obtained by using on-line solid phase extraction followed by liquid chromatography-diode array detection (on-line SPE-LC-DAD). The correlation between both techniques was good when analyzing levels of atrazine ranging from 0.01 to 5 μg/l in samples showing salt concentration values varying from 0 to 35 g/l and pH values from 2 to 10. One of these immunoassays (Atrazine High-Sensitivity RaPID assay) was employed to directly analyze atrazine in real estuarine and coastal water samples. The same samples were analyzed after filtration and C18 Empore disks extraction.
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| 4. |
- Hedenfalk, M., et al.
(författare)
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Modulation of the measuring range of a radioimmunoassay using an organic water two phase system
- 1997
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 341:2-3, s. 269-274
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Tidskriftsartikel (refereegranskat)abstract
- A commercially available radioimmunoassay (RIA) kit was used to study the effects of organic solvents on antigen-antibody interactions. The RIA analysis was carried out in aqueous-organic two phase systems. After exposure to hydrophobic organic solvents the antibodies retained full binding capacity, while less hydrophobic solvents caused partial inactivation of the antibodies. A practical analysis for digoxigenin in organic solvents was developed using the RIA kit with polyclonal antibodies against digoxin. The sensitivity was modulated four orders of magnitude by the choice of organic solvent. The main factor influencing the sensitivity was the partitioning of digoxigenin between the aqueous and the organic phases. The technique developed is promising for the analysis of a variety of antigens dissolved in organic solvents.
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| 5. |
- Mecklenburg, M., et al.
(författare)
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Differentiation of human serum samples by surface plasmon resonance monitoring of the integral glycoprotein interaction with a lectin panel
- 2002
-
Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 459:1, s. 25-31
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial infection and inflammation result in massive changes in serum glycoproteins. These changes were investigated by the interaction of the saccharide glycoprotein moiety with lectins. A panel of eight lectins (Canavalia ensiformis, Bandeiraea simplicifolia BS-I, Arachis hypogaea, Phytolacca americana, Phaseolus vulgaris, Artocarpus integrifolia, Triticum vulgaris and Pisum sativum) was used to differentiate human serum glycoproteins obtained from patients with various bacterial infections. Lectin functionalised sensing layers were created on gold-coated wafers and lectin-glycoprotein interactions were monitored by surface plasmon resonance. The interaction of the lectin panel with serum glycoproteins produces unique patterns. Principal component analysis (PCA) was used to analyse the patterns. The actual panel of eight lectins enabled discrimination between sera obtained from patients sick with bacterial infection and healthy patients. Extended lectin panels have the potential to distinguish between types of bacterial infection and identify specific disease state. © 2002 Elsevier Science B.V. All rights reserved.
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| 6. |
- Miyabayashi, Akiyoshi, et al.
(författare)
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A potentiometric enzyme electrode for monitoring in organic solvents
- 1989
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 219:C, s. 27-36
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Tidskriftsartikel (refereegranskat)abstract
- A potentiometric enzyme electrode is described for monitoring reactions in organic solvents. By use of an enzyme deposited on magnetic particles which are attracted to the tip of the electrode by means of a magnetic field, it is possible to produce an electrode in which the enzyme can easily be exchanged. As an example, studies of the chymotrypsin-catalyzed ester synthesis in diisopropyl ether and in toluene at varying water contents are reported. The results are consistent with those obtained from batch experiments. Operational behaviour and signal stability of the system makes this kind of potentiometric enzyme electrode attractive for monitoring bioorganic processes.
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| 7. |
- Momeni, Naghi, et al.
(författare)
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CCD-camera based capillary chemiluminescent detection of retinol binding protein
- 1999
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 387:1, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- A chemiluminescence (CL) assay for retinol-binding protein (RBP) was designed and optimized using a charge coupled device (CCD)-camera based detection system. A sandwich ELISA was designed based on the anti-RBP antibodies immobilized in glass capillaries pre-treated with silica sol. The immobilization was predominantly by physisorption of the protein on the silica surface. The RBP bound to the anti-RBP antibodies was detected by using an anti-RBP-horseradish peroxidase (HRP) conjugate. The reaction of the HRP with hydrogen peroxide and luminol and 4-iodophenol generated the CL. The CL emitted from the glass capillaries was detected by a cooled slow scan CCD camera at an optimized exposure time. The approximately linear range of RBP determination was between 11 pg ml−1 and 11 ng ml−1 with a coefficient of variation of 5–11% (n=6) over this range.
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| 8. |
- Tang, Xiao-Jing, et al.
(författare)
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Polyethyleneimine-coated reticulated vitreous carbon electrode with immobilized enzymes as a substrate detector
- 1998
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 374:2-3, s. 185-190
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Tidskriftsartikel (refereegranskat)abstract
- Polyethyleneimine (PEI) was covalently coupled to carbodiimide-activated reticulated vitreous carbon (RVC). The PEI-coated RVC was activated with glutaraldehyde, and glycerol dehydrogenase and diaphorase were then immobilized. The PEI-coated RVC with immobilized enzymes functioned both as an enzyme reactor and a working electrode in an amperometric detection system where NAD+/NADH was recycled by the immobilized enzymes. The coated RVC electrode showed good properties compared to uncoated RVC, such as a long lifetime and a constant response to a series of injections in a flow-injection system, resulting in a relative standard deviation of 1.4%. The calibration graph was linear from the detection limit 0.1μM to 2mM NADH in the absence of recycling.
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| 9. |
- Xie, Bin, et al.
(författare)
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Microbiosensor based on an integrated thermopile
- 1994
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 299:2, s. 165-170
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Tidskriftsartikel (refereegranskat)abstract
- A microbiosensor based on an integrated thermopile was designed and fabricated on a quartz chip. The thermopile, which was manufactured by doping boron in polysilicon together with aluminium, provided a potential output of ca. 2 mV K. A silicone rubber membrane was used to form and seal the microchannel. The total column volume was 20 μl. Glucose oxidase and catalase were co-immobilized on spherical CPG beads (controlled pore glass) and in turn charged into the microchannel. Using 1 μl sample volumes, a linear range of 2 to 25 mM glucose was obtained using a flow rate of 105 μl min. The relative standard deviation for 100 glucose samples (10 mM) was 5%.
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| 10. |
- Ye, Lei, et al.
(författare)
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Molecular imprinting on microgel spheres
- 2001
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 435:1, s. 187-196
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Tidskriftsartikel (refereegranskat)abstract
- Molecularly imprinted polymers have been prepared in various configurations including, for example, polymer beads, monoliths and membranes for different applications. The most common form of imprinted polymer is, however, still the irregularly shaped particle obtained by grinding the traditional, macroporous polymer monolith. We herein present a novel and efficient approach leading to imprinted microspheres, i.e. microgels bearing binding sites specific to target molecules. Imprinted microgels are proposed to be the basic components in previously reported, molecularly imprinted, cross-linked polymers, although the polymers themselves may exist in different forms depending on the preparation method utilised. Chemical modification of the molecularly imprinted microspheres introduces additional functionalities that may be used to couple sensing elements in various assay formats, or for the immobilisation of the imprinted microspheres on various transducers towards the development of biomimetic sensors.
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| 11. |
- Adbo, Karina, et al.
(författare)
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Study of the kinetics of enantioselective solid-phase extraction on Tröger’s base molecularly imprinted polymers
- 2001
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 435:1, s. 115-120
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Tidskriftsartikel (refereegranskat)abstract
- Molecularly imprinted polymers (MIPs) selective for Tröger’s base were designed and synthesised, and HPLC-chromatographic evaluation of polymer recognition characteristics was undertaken. Baseline separation of racemic Tröger’s base was readily achieved, and enantioseparation factors (α) of up to 4.8±0.2 were obtained. The high enantioselectivity demonstrated by these materials prompted their use to examine the kinetics and thermodynamics of individual enantiomers in a solid-phase extraction (SPE) process. Enantiomer-dependent differences in the rates and extent of adsorption were observed. Furthermore, the enantiomeric enrichment of racemates was demonstrated in batch studies.
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| 12. |
- Allender, Chris J., et al.
(författare)
-
Preface
- 2001
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 435:1, s. 1-2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 13. |
- Artursson, Tom, et al.
(författare)
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Variable reduction on electronic tongue data
- 2002
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 452:2, s. 255-264
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Tidskriftsartikel (refereegranskat)abstract
- Reduction of the number of variables in data from a so-called electronic tongue contributes to simpler model calculations and less storage requirements. In this study, we have developed a model for this purpose. This model describes the response from the electrodes in the electronic tongue with two exponential functions plus a constant term, i(t) = k + kf e-ta + kc e-tß, where t is the time. From the model, five parameters which describe the signal are extracted. These parameters can be used as inputs instead of the original signal to any multivariate algorithm. The results show that the variables obtained are at least as good as the original data to separate between different classes, even though the number of parameters has been reduced between 80 and 199 times. © 2002 Elsevier Science B.V. All rights reserved.
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| 14. |
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| 15. |
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| 16. |
- Dahlqvist, Ralf, et al.
(författare)
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Performance of the diffusive gradients in thin films technique for measuring Ca and Mg in freshwater
- 2002
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 460:2
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of the major cations Ca and Mg by the technique of diffusive gradients in thin films (DGTs) were systematically evaluated. The concentration in solution was calculated using Fick's first law of diffusion from the directly measured flux to the DGT device. A selective cation exchange resin (Bio-Rad Chelex®100), which has been used extensively with DGT for trace metals, such as Cd2+, Cu2+ and Ni2+, was used for this work. Elution of Ca and Mg from the resin with 1 M HNO3 was very reproducible. Measurements of Ca and Mg concentrations in synthetic solutions agreed well with the theoretical predictions. The negative response on uptake caused by lowered pH was investigated. Uptake was found to decline below pH 5. The capacity of the DGT device for Ca and Mg was also investigated to establish maximum deployment times for given concentrations. Experiments with filtered and modified lake water show that DGT can be used to measure Ca and Mg when trace metals are present in the solution. An in situ deployment of DGT combined with an ultrafiltration study suggest that the Mg concentration measured by DGT is similar to the concentration found in the fraction <1 kDa.
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| 17. |
- Danielsson, Rolf, et al.
(författare)
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Matched filtering with background suppression for improved quality of base peak chromatograms and mass spectra in liquid chromatography-mass spectrometry
- 2002
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 454:2, s. 167-184
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Tidskriftsartikel (refereegranskat)abstract
- A time domain filter that combines the properties of matched filtering and two-fold differentiation is presented. The filter coefficients are given by the second derivative of a Gaussian model peak, controlled by the setting of two parameters related to the chromatographic system. The fundamental characteristics of the filter were derived, and its applicability demonstrated for real liquid chromatography–mass spectrometry (LC–MS) data. The filter is primarily intended as a fast pre-processing step, for a mass chromatogram with 320 scans over 700 mass channels the computation time was 0.6 s on a standard PC. Base peak chromatograms with improved peak detection capability and mass spectra useful for compound identification were obtained with filtered data. The most significant effect of the described filter is background reduction due to the differentiation, which in combination with the matched filter can be performed with maintained or even improved signal-to-noise ratio.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Ivansson, D., et al.
(författare)
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Quantitation of intracellular recombinant human superoxide dismutase using surface plasmon resonance
- 2002
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 456:2, s. 193-200
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Tidskriftsartikel (refereegranskat)abstract
- An immunosensor assay for the quantitation of intracellular recombinant human superoxide dismutase (rhSOD) in Escherichia coli cultivations based on detection with surface plasmon resoance (SPR) is described. A monoclonal antibody for rhSOD was immobilized on a SPR dextran gold chip. Bacterial samples were sonicated and centrifugated prior to injection over the antibody chip for SPR detection. The assay time was 7min and allowed quantitation in the range of 1-64nM SOD in lysate samples with a precision of 1.1-3.4%. The assay was applied to monitor the concentration of rhSOD during E. coli bioreactor cultivations where the rhSOD production was induced by iso-propyl-b-D-thiogalactoside (IPTG). The assay allowed accurate monitoring of the production of rhSOD where the important phases in the product formation were possible to see. The report also discusses influence from sample preparation, SPR selectivity and sensitivity and quantitation limits. The assay proved to be fast, sensitive and accurate with low background effects from the dextran matrix of the SPR chip. ⌐ 2002 Published by Elsevier Science B.V.
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| 22. |
- Ivarsson, Patrik, et al.
(författare)
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Comparison of a voltammetric electronic tongue and a lipid membrane taste sensor
- 2001
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 449:1-2, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- An electronic tongue based on voltammetry and a multichannel lipid membrane taste sensor based on potentiometry are compared using two aqueous examples: detergents and teas. The electronic tongue consists of four electrodes of different metals, a reference electrode and a counter electrode. The measurement principle is based on pulse voltammetry in which current is measured during the change of the amplitude of the applied potential. The taste sensor is based on eight different lipid/polymer membranes. The voltage difference between the electrodes and an Ag/AgCl reference electrode is measured when the current is close to zero. The responses from the two sensors systems are treated separately with multivariate data analysis based on principal component analysis and then merged to examine if further information could be extracted. It is shown that although the two sensor systems are about equal in separation ability in the two cases, extra information can be gained by combination of the two sensor systems. © 2001 Elsevier Science B.V. All rights reserved.
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| 23. |
- Jonsson, Tobias, et al.
(författare)
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Heterocyclic compounds as catalysts in the peroxyoxalate chemiluminescence reaction of bis(2,4,6-trichlorophenyl)oxalate
- 1998
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Ingår i: Analytica Chimica Acta. - Amsterdam : Elsevier. - 0003-2670 .- 1873-4324. ; 361:3, s. 205-215
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Tidskriftsartikel (refereegranskat)abstract
- Substituted imidazoles and leaving groups known from other areas of chemistry have been tested for catalytic efficiency in the peroxyoxalate chemiluminescence (PO-CL) reaction, using bis(2,4,6-trichlorophenyl)oxalate (TCPO) as reagent. Catalytic activity was found for 1,2,4-triazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole and 4,5-dichloroimidazole, while 2-mercaptoimidazole, 2-nitroimidazole, 4-nitroimidazole, benzimidazole, benzotriazole, thiazole, o-benzoic sulfimide, phthalimide, succinimide, 2(1H)-pyridone and 1,2,3-benzotriazine-4(3H)-one yielded no detectable chemiluminescence under the conditions used. None of the tested compounds was more efficient than imidazole in catalyzing the PO-CL reaction. Spectrophotometric measurements of the catalytic breakdown of TCPO showed that an intermediate was formed with almost all catalysts, and that intermediates that were more stable or present at lower concentration led to a reduced catalytic efficiency in the PO-CL reaction of TCPO.
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| 24. |
- Jonsson, Tobias, et al.
(författare)
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Very fast peroxyoxalate chemiluminescence
- 1999
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Ingår i: Analytica Chimica Acta. - Amsterdam : Elsevier. - 0003-2670 .- 1873-4324. ; 400:1-3, s. 257-264
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Tidskriftsartikel (refereegranskat)abstract
- Peroxyoxalate chemiluminescence (PO-CL) detection offers an advantage in chromatographic detection, by the virtue of its multiple unique selectivities and high sensitivity. However, many of the analytical separation techniques available today require observation times in the millisecond range to preserve the band resolution, and as the reaction kinetics of the PO-CL reaction is considerably slower, extra flow elements are needed to observe the reaction in a time window at maximum emission intensity. Since these flow elements increase the complexity of the system and contribute to band-broadening, the rational way to adapt PO-CL detection to miniaturised separation systems is to speed up the reaction, so that it emits an initial burst of light within the acceptable detection time-frame. Although this may result in a lower overall quantum yield, the actual detection sensitivity could be equal to, or better than slower PO-CL systems. By making careful selections of oxalic reagent and catalyst(s) the reaction can be fine-tuned to maximise the intensity. In this work, the time-dependent light emission from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) was studied under the catalytic influence of imidazole, 1,2,4-triazole, 4-dimethylaminopyridine (DMAP), and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) in acetonitrile. Both DMAP and DBU accelerated the reaction substantially, but the best combination of reaction speed and intensity was found for a mixture of 0.5 mM DBU and 5 mM 1,2,4-triazole, which reached its maximum emission after only 40 ms and had an emission intensity comparable to that seen with 5 mM imidazole as catalyst.
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| 25. |
- Jungar, Christina, et al.
(författare)
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Neoglycoconjugates as affinity ligands in surface plasmon resonance analysis
- 2001
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 449:1-2, s. 51-58
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Tidskriftsartikel (refereegranskat)abstract
- Neoglycoconjugates, i.e. de novo synthesized conjugates of glycosides and carrier molecules such as proteins or polylipids, were used as affinity ligands in a surface plasmon resonance (SPR) biosensor assay. The affinity of the glycoconjugates, normally in the lower affinity range, was influenced by increasing the number of glycosides bound per carrier protein, the coupling chemistry, and the assay temperature. As a model system, albumin-conjugated A- and B-active blood group oligosaccharides with suitable linker molecules were chosen. Specific monoclonal antibodies were used as analytes to verify the interactive performance. Affinity kinetics of the systems were evaluated from the SPR biosensor data. The results demonstrate that neoglycoconjugates are a good alternative in presenting affinity ligands of small, specific molecules in SPR-based assays with retained specificity and bioavailability. ⌐ 2001 Elsevier Science B.V. All rights reserved.
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| 26. |
- Kalman, E.-L., et al.
(författare)
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Classification of complex gas mixtures from automotive leather using an electronic nose
- 2000
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 403:1-2, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- A semiconductor gas sensor array combined with a routine for pattern recognition - a so-called electronic nose - for the detection of gas emissions from the leather used in car compartments is described. The gas sensors are 10 metal oxide semiconductor field effect transistors (MOSFETs) with gates of thin, catalytic metals, and five semiconducting metal oxide sensors. The sensor array data are processed by multivariate means using principal component analysis (PCA) and are shown to give similar and add additional information compared to gas chromatography-mass spectrometry (GC- MS) and a human sensory panel. The total volatile organic compound concentration as measured by GC did not differ between good and bad samples and could therefore not be used as a quality control tool, whilst the electronic nose together with pattern recognition could readily discover the deviating samples with unusual emitting gases. This set-up could be useful in on-line quality monitoring systems to detect anomalies in incoming car interior trim materials.
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| 27. |
- Krantz-Rülcher, Christina, et al.
(författare)
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Electronic tongues for environmental monitoring based on sensor arrays and pattern recognition : A review
- 2001
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 426:2, s. 217-226
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of sensor arrays and pattern recognition applied to the obtained signal patterns for environmental monitoring are discussed in some detail. Different types of electronic tongues are described and evaluated for monitoring purposes. More specifically the performance of multielectrode arrays used for voltammetric analysis of aqueous samples is described. It is, e.g. shown how such an 'electronic tongue' can be used to monitor the quality of water in a production plant for drinking water. It is pointed out that the concepts of 'electronic noses' and 'electronic tongues' often predict a quality of a sample rather than giving exact information about concentrations of individual species. (C) 2001 Elsevier Science B.V.
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| 28. |
- Larsson, H, et al.
(författare)
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Liquid core waveguide-based optical spectrometry for field estimation of dissolved BTEX compounds in groundwater - A feasibility study
- 2003
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 485:2, s. 155-167
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Tidskriftsartikel (refereegranskat)abstract
- The utility of a liquid core waveguide (LCW) system for acting as a sentry monitor for compounds such as benzene, toluene, ethylbenzene, xylene (BTEX) in water was examined. A vapor-permeable LCW suitable for long path length absorbance spectroscopy based on a Teflon AF 2400 tube was fabricated. Multiwavelength spectroscopy in the near-UV was carried out using a fiber optic-based flashlamp-photodiode array (PDA) combination with hexane as the solvent in the waveguide core. Using multicomponent calibration, quantitation of benzene and toluene accurate to 6+/-5% could be conducted at sub-mg l(-1) levels in mixtures after a sampling period of 10 min. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 29. |
- Larsson, Ted, et al.
(författare)
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Electron transfer between cellobiose dehydrogenase and graphite electrodes
- 1996
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 331:3, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- Electron transfer between the enzyme cellobiose dehydrogenase (CDH) and a flavin adenine dinucleotide (FAD) containing a catalytic active fragment of CDH (FAD-fragment) and a graphite electrode, respectively, was established. The current response in the presence of the enzyme substrate for graphite electrodes with CDH or the FAD-fragment adsorbed on the freshly polished graphite surface were compared with that of electrodes where CDH or the FAD-fragment were crosslinked in a redox polymer at the electrode surface. The initial slope, dj/d[S](S=0), where j is the current density and [S](S=0) the zero substrate concentration, was taken as a measure of the substrate response. For the electrodes with enzymes adsorbed directly on the surface, dj/d[S](S=0), was a factor of 3 lower than for electrodes prepared with the polymer mixture. The redox polymer based electrodes, with CDH and with FAD-fragment, both showed a high and close to equal substrate response. In contrast the surface adsorbed CDH gave a much higher substrate response than the FAD-fragment.
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| 30. |
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| 31. |
- Lutz, Mareike, 1967-, et al.
(författare)
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Effects of different additives on a tyrosinase based carbon paste electrode
- 1995
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Ingår i: Analytica Chimica Acta. - Amsterdam : Elsevier. - 0003-2670 .- 1873-4324. ; 305:1-3, s. 8-17
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Tidskriftsartikel (refereegranskat)abstract
- The influence of a number of solid and chemical additives on the sensitivity and operational stability of a tyrosinase carbon paste electrode was studied. Cyclic voltammograms were run of the electrochemically active catechol/o-quinone couple on unmodified and additive modified carbon paste electrodes without tyrosinase. This was done in order to study the influence of these additives on the pure electrochemistry of the carbon paste. The influence on the total system (additive and enzyme modified carbon paste electrode) was studied in the flow injection mode. In some instances a dramatic improvement of the direct electron transfer of the catechol/o-quinone couple was obtained with both solid and chemical additives included in the carbon paste. A similar improvement of biosensor sensitivity in the flow injection mode was obtained with most chemical additives whereas the solid additives had a negative impact on biosensor sensitivity. The results obtained in this work indicate that these additives influence the purely electrochemical processes at the carbon paste and/or the performance of the enzyme in the carbon paste environment. How and why these additives can possibly influence the biosensor performance are discussed. © 1995.
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| 32. |
- Malinovskiy, Dmitry, et al.
(författare)
-
Simplified method for the Re-Os dating of molybdenite using acid digestion and isotope dilution ICP-MS
- 2002
-
Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 463:1, s. 111-124
-
Tidskriftsartikel (refereegranskat)abstract
- An analytical method was developed for Os-Re dating of molybdenite. The method is based on determination of Os and Re concentrations in molybdenite by isotope dilution inductively-coupled plasma mass spectrometry (ID-ICP-MS). Sample digestion and sample/spike equilibration were achieved by a two-stage autoclave-based procedure using a mixture of nitric and sulphuric acids. Os was separated from the sample digest by modified single-stage distillation of osmium tetraoxide (OsO4) using elevated temperature and on-line addition of hydrogen peroxide. OsO4(g) was trapped in a mixture of 0.05% thiourea in 0.05 M sodium hydroxide. An anion-exchange column was used to separate Re from excess Mo in the solution remaining after distillation. Os and Re isotope ratio measurements were performed by single-collector, double focusing inductively-coupled plasma mass spectrometry (ICP-MS) with on-line mass-bias correction. Typical instrumental precision was in the range 0.02-0.2% relative standard deviation (R.S.D.) depending on the analyte concentrations. Notorious Os memory effects in the ICP-MS introduction system were eliminated using 5% ammonia solution, both as matrix for final dilution of the trap mixture as well as for washing between the samples. The reproducibility of the entire analytical procedure was accessed by replicate dating of two molybdenite standards and three molybdenite separates, and was found to be in the range 0.87-1.52% R.S.D. Though accuracy of the method is limited by difficulties in evaluating exact concentration of Os in spike solution, ages obtained in the course of these work agrees well with previously published data.
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| 33. |
- Nording, Malin, 1976-, et al.
(författare)
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Evaluation of the structure/cross-reactivity relationship of polycyclic aromatic compounds using an enzyme-linked immunosorbent assay kit
- 2003
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 487:1, s. 43-50
-
Tidskriftsartikel (refereegranskat)abstract
- A commercially available enzyme-linked immunosorbent assay (ELISA) kit, the PAH soil test, was evaluated with regard to cross-reactivity. Phenanthrene in methanol was used as reference substance. Anthracene, naphthalene and fluorene were chosen as representatives of the 16 US-EPA priority-pollutant polycyclic aromatic hydrocarbons (PAHs). In addition, a number of polycyclic aromatic compounds (PACs), including methyl-, phenyl-, and carbonyl-PAHs, as well as NSO-heterocyclic PACs, found at former industrial sites, were chosen for elucidation of structure/cross-reactivity relationships. The study emphasizes the importance of a priori knowledge of sample composition for accurate interpretation of test results.
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| 34. |
- Palleschi, G., et al.
(författare)
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Amperometric tetrathiafulvalene-mediated lactate electrode using lactate oxidase absorbed on carbon foil
- 1990
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 234:2, s. 459-463
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The features of a new sensor for determining l-lactate are reported. The enzyme lactate oxidase and the mediator, tetrathiafulvalene (TTF), are absorbed on carbon foil disks previously bonded onto the ends of glass tubes. Linear calibration graphs were obtained in the range 10−4−10−3 M with physiological phosphate buffer (pH 7.35) and at 30°C with a response time of a few seconds. Calibration graphs in the range 10−3−10−2 M were also obtained and the difference in response times between these two ranges were investigated. The results are promising for assembling disposable lactate sensors for in vitro or for in or ex vivo measurements.
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| 35. |
- Piletska, Elena V., et al.
(författare)
-
Biotin-specific synthetic receptors prepared using molecular imprinting
- 2004
-
Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 504:1, s. 179-183
-
Tidskriftsartikel (refereegranskat)abstract
- The composition of new molecularly imprinted polymers (MIPs) specific for biotin was optimised using molecular modelling software. Three functional monomers: methacrylic acid (MAA), 2-(trifluoromethyl)acrylic acid (TFAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPSA), which demonstrated the highest binding scores with biotin, were tested on their ability to generate specific binding sites. The imprinted polymers were photografted to the surface of polystyrene microspheres in water. The affinity of the synthetic "receptor" sites was evaluated in binding experiments using horseradish peroxidase-labelled biotin. Good correlation was found between the modelling results and the performance of the materials in the template re-binding study. The dissociation constants for all MIPs were 1.4-16.8 nM, which is sufficient for most analytical applications where biotin is used as a label.
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| 36. |
- Piletsky, Sergey, et al.
(författare)
-
Custom synthesis of molecular imprinted polymers for biotechnological application - Preparation of a polymer selective for tylosin
- 2004
-
Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 504:1, s. 123-130
-
Tidskriftsartikel (refereegranskat)abstract
- A molecularly imprinted polymer (MIP) selective for tylosin was designed and synthesised using a computational method (MIP "dialling"). In re-binding experiments the MIP demonstrated high affinity for tylosin in aqueous solutions and in organic solvents. The synthesised polymer was tested for re-binding with the template and related metabolites such as tylactone, narbomycin and picromycin. The HPLC analysis showed that the computationally designed polymer is specific and capable of separating the template from its structural analogues. The MIP was capable of recovering tylosin from broth samples. The polymer capacity for tylosin was estimated as 6.4 mg/g for MIP, which was suitable for practical application and tylosin recovery from broth samples. Among the advantages of this was the possibility to adsorb tylosin from a complex media with easy removal of oils and other impurities which are present in significant quantities, which can create problems for its chromatographic purification procedure. The MIP "dialling" procedure can have a general significance for the fast preparation of specific adsorbents for biotechnological applications.
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| 37. |
- Rodushkin, Ilya, et al.
(författare)
-
Comparison of two digestion methods for elemental determinations in plant material by ICP techniques
- 1999
-
Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 378:1-3, s. 191-200
-
Tidskriftsartikel (refereegranskat)abstract
- Two digestion procedures have been tested on plant samples for application in the determination of a wide range of major, minor, and trace elements by a combination of inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The first is an open-vessel digestion with concentrated nitric acid and the second is a microwave digestion with a mixture of concentrated nitric acid and hydrogen peroxide. The detection limits were found to be controlled by instrumental capabilities in ICP-AES and by digestion blank levels in ICP-MS. The accuracy of the overall analytical procedures was estimated by analysis of a certified reference material. Among elements for which certified concentrations are available, good agreement between measured and reference values was found for 15 and 16 elements in the first and second procedure, respectively. The precision was assessed from replicate analysis (including sample preparation) of reference material and a number of environmental samples and was found to be 5% RSD or better when analyte concentration exceeds quantification limit. Owing to the multielemental capabilities and to the wide analytical range of the ICP techniques used, more than 30 elements can be determined in plant materials at concentrations varying from tens of pg g-1 to wt%.
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| 38. |
- Sandberg Hiltunen, Maria, 1966-
(författare)
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DNA and peptide sequences and chemical processes multivariately modelled by principal component analysis and partial least-squares projections to latent structures
- 1993
-
Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 277, s. 239-253
-
Tidskriftsartikel (refereegranskat)abstract
- Biopolymer sequences (e.g., DNA, RNA, proteins and polysaccharides) and chemical processes (e.g., a batch or continuous polymer synthesis run in a chemical plant) have close similarities from the modelling point of view. When a set of sequences or processes is characterized by multivariate data, a three-way data matrix is obtained. With sequences the position and with processes the time is one direction in this matrix. The multivariate modelling of this matrix by principal component analysis (PCA) or partial least-squares (PLS) methods for the following purposes is discussed: classification of sequences; quantitative relationships between sequence and biological activity or chemical properties; optimizing a sequence with respect to selected properties; process diagnostics; and quantitative relationships between process variables and product quality variables. To obtain good models, a number of problems have to be adequately dealt with: appropriate characterization of the sequence or process; experimental design (selecting sequences or process settings); transforming the three-way into a two-way matrix; and appropriate modelling and validation (modelling interactions, periodicities, “time series” structures and “neighbour effects”). A multivariate approach to sequence and process modelling using PCA and PLS projections to latent structures is discussed and illustrated with several sets of peptide and DNA promoter data.
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| 39. |
- Simpson, S L, et al.
(författare)
-
Flow injection determination of Al3+ and Al13O4(OH)(24)(H2O)(12)(7+) species using a 1.3-s reaction with 8-quinolinol-derivatised Fractogel
- 1997
-
Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 343:1-2, s. 19-32
-
Tidskriftsartikel (refereegranskat)abstract
- Speciation of Al is determined by a 1.3-s reaction with 8-quinolinol (oxine)-derivatised Fractogel in a 22 μl column reactor in a flow injection (FI) manifold. Al (pre)concentrated on the column from a 650 μl sample is selectively eluted with 250 μl of 0.02 M NaOH and detected spectrophotometrically as the Al-chrome azurol S (CAS) complex at pH 5.0. This Al (referred to as ‘free Al’) comprises Al3+ + A1(OH)2+ + Al in very labile complexes. Tests with synthetic solutions established that Al is not significantly sequestered from the citrate, oxalate and malonate complexes. Al-hydroxo polymers [Al13(OH)327+] are quantitatively retained by the column but are not desorbed by 0.02 M NaOH in the time frame of the FI method; therefore they do not contribute to the analytical signal. However, they can be quantified after stopped-flow elution with 0.2 M NaOH. The AlF2+ and AlF2+ complexes are retained and eluted quantitatively and therefore contribute to the measurement of ‘free Al’. The method has been applied to humic waters and soil solutions and the results for ‘free’ Al3+ compared with those obtained by the 7-s CAS method. The method has a 2σ detection limit of 70 nM, a linear working range of 0.3–16 μM and relative standard deviations of 7% and 1% at 0.5 and 16 μM, respectively.
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| 40. |
- Simpson, S L, et al.
(författare)
-
Kinetic and thermodynamic considerations in the determination of aluminium using pyrocatechol violet : implications for the use of 'kinetic-based' determinations of metal ions in natural systems
- 1998
-
Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 359:3, s. 329-340
-
Tidskriftsartikel (refereegranskat)abstract
- Kinetic and thermodynamic factors associated with the use of pyrocatechol violet (PCV) for the determination of total reactive Al or `free' Al[Al3++Al(OH)2++Al(OH)+2] have been investigated. The rate of reaction of Al with PCV (in MES buffer, pH 6.2) was strongly influenced by the presence of competing ligands. The rate of formation of Al(PCV)2 on the addition of Al3+ to a PCV–competing ligand mixture was: oxalate≈F−≈malonate>salicylate>>no competing ligand>citrate. A similar increase in the reaction rate relative to standards (i.e. no competing ligand) was observed for Al pre-equilibrated in humic waters and soil solution (at concentrations above or below the Al-complexation capacity). The discrepancy in reaction rates may be ascribed to the inhibition through pH-induced hydrolysis of Al3+ in the absence of ligands (i.e. in standards) or to acceleration in the presence of naturally occurring ligands. It has serious implications for the use of kinetic-based FIA protocols for the determination of Al fractions or total Al in natural waters. Specifically, the (usually) slower reaction for Al3+standards implies that measurements on systems containing organic ligands may overestimate the concentration of `free' or total Al. Quantitative studies on the thermodynamics of the citrate–Al3+–PCV system established that the attainment of equilibrium in the pH range 5.0 to 6.6 required ≈300 min. Thus, determination of total Al by FIA in systems containing this or closely related ligands is not feasible.
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| 41. |
- Winquist, Fredrik, et al.
(författare)
-
A hybrid electronic tongue
- 2000
-
Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 406:2, s. 147-157
-
Tidskriftsartikel (refereegranskat)abstract
- A hybrid electronic tongue is described based on a combination of potentiometry, voltammetry and conductivity. It was used for classification of six different types of fermented milk. Using ion-selective electrodes, pH, carbon dioxide and chloride ion concentrations were measured. The voltammetric electronic tongue consisted of six working electrodes of different metals (gold, iridium, palladium, platinum, rhenium and rhodium) and an Ag/AgCl reference electrode. The measurement principle is based on pulse voltammetry in which current transients are measured due to the onset of voltage pulses at decreasing potentials. The data obtained from the measurements were treated by multivariate data processing based on principal components analysis and an artificial neural net. The hybrid tongue could separate all six samples. Also, the nature of the micro-organisms in the different fermentations was reflected in the principal component analysis. Copyright (C) 2000 Elsevier Science B.V.
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| 42. |
- Winquist, Fredrik, et al.
(författare)
-
Determination of ammonia in air and aqueous samples with a gas-sensitive semiconductor capacitor
- 1984
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 164, s. 127-138
-
Tidskriftsartikel (refereegranskat)abstract
- The properties of a new type of ammonia gas-sensitive semiconductor capacitor are described. The sensor is based on a palladium MOS field-effect capacitor with a thin layer (3 nm) of iridium surrounding the palladium gate. The lower limit of detection for ammonia in air is 1 ppm (0.59 mg kg−1). The analytical characteristics and temperature-dependence of the sensor in measurements of ammonia in air are evaluated. Ammonia in aqueous solutions is determined by the use of a continuous flow system utilizing a gaspermeable membrane in combination with the sensor. The calibration plot of the voltage drop of the capacitor vs. ammonia concentration in 150-μl samples is linear in the concentration range 0.2 × 10−6–5 × 10−5 M. Ammonia is determined in rain and river water as well as in whole blood and blood serum; 15 samples per hour can be assayed. Analytical recovery studies and the selectivity properties of the system are described and discussed. Finally, the properties of the flow-through system in continuous monitoring are described.
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| 43. |
- Winquist, Fredrik, et al.
(författare)
-
Determination of urea with an ammonia gas-sensitive semiconductor device in combination with urease
- 1984
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 163, s. 143-149
-
Tidskriftsartikel (refereegranskat)abstract
- An ammonia gas-sensitive Ir/Pd MOS capacitor is used for urea determinations with the aid of urease in two different systems. One combination utilizes a reaction column with immobilized urease in a flow-injection system. The lower limit of urea detection for 150-μl samples was 0.2 μM. Urea in whole blood and blood serum was determined after a 500-fold dilution, and 15 samples per hour could be assayed. The relative standard deviation was 4.6% (n=10). Recovery tests were satisfactory. Values obtained for urea in serum correlated well with those from a spectrophotometric method. The other combination is based on a small flow cell with free urease enclosed between a dialysis membrane and a gas-permeable membrane. Urea was determined in the concentration range 0.01–50 mM. The enzyme probe could be used for up to four days without changes of behaviour.
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| 44. |
- Winquist, Fredrik, et al.
(författare)
-
Flow injection analysis applied to a voltammetric electronic tongue
- 2002
-
Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 471:2, s. 159-172
-
Tidskriftsartikel (refereegranskat)abstract
- A measurement system, based on flow injection analysis (FIA) technique applied to a voltammetric electronic tongue is described. A reference solution was thus continuously pumped through a cell with a voltammetric electronic tongue, and test samples were injected into the flow stream. Responses were obtained by measuring the resulting pulse height. The FIA technique offered several advantages, since relative measurements are performed, the system is less influenced by sensor baseline drift, calibration samples and/or washing solutions can be injected within a measurement series, and the system is well adapted for automatization. The system was used to analyze standard solutions of H2O2, KCl, CuNO3, K4[Fe(CN)6], K3[Fe(CN)6] and NaCl, and results obtained were treated with multivariate data analysis. Principal component analysis performed showed that electrode drift could be considerably decreased, and the set-up was also used for classification of different apple juices. © 2002 Elsevier Science B.V. All rights reserved.
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| 45. |
- Abbas, Aamer, 1973, et al.
(författare)
-
Chemical images of marine bio-active compounds by surface enhanced Raman spectroscopy and transposed orthogonal partial least squares (T-OPLS)
- 2012
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 737, s. 37-44
-
Tidskriftsartikel (refereegranskat)abstract
- Surface enhanced Raman spectroscopy combined with transposed Orthogonal Partial Least Squares (T-OPLS) was shown to produce chemical images of the natural antibacterial surface-active compound 1,1,3,3-tetrabromo-2-heptanone (TBH) on Bonnemaisonia hamifera. The use of gold colloids function-alised with the internal standard 4-mercapto-benzonitrile (MBN) made it possible to create images of the relative concentration of TBH over the surfaces. A gradient of TBH could be mapped over and in the close vicinity of the B. hamifera algal vesicles at the attomol/pixel level. T-OPLS produced a measure of the spectral correlation for each pixel of the hyperspectral images whilst not including spectral variation that was linearly independent of the target spectrum. In this paper we show the possibility to retrieve specific spectral information with a low magnitude in a complex matrix.
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| 46. |
- Abdel-Rehim, Mohamed
(författare)
-
Microextraction by packed sorbent (MEPS) : A tutorial
- 2011
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 701:2, s. 119-128
-
Tidskriftsartikel (refereegranskat)abstract
- This tutorial provides an overview on a new technique for sample preparation, microextraction by packed sorbent (MEPS). Not only the automation process by MEPS is the advantage but also the much smaller volumes of the samples, solvents and dead volumes in the system. Other significant advantages such as the speed and the simplicity of the sample preparation process are provided. In this tutorial the main concepts of MEPS will be elucidated. Different practical aspects in MEPS are addressed. The factors affecting MEPS performance will be discussed. The application of MEPS in clinical and pre-clinical studies for quantification of drugs and metabolites in blood, plasma and urine will be provided. A comparison between MEPS and other extraction techniques such as SPE, LLE, SPME and SBSE will be discussed. (C) 2011 Elsevier B.V. All rights reserved.
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| 47. |
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| 48. |
- Abrahamsson, Victor, et al.
(författare)
-
Supercritical fluid extraction of lipids from linseed with on-line evaporative light scattering detection.
- 2015
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 853, s. 320-327
-
Tidskriftsartikel (refereegranskat)abstract
- Supercritical fluid extraction (SFE) is a green alternative method of extraction for neutral lipids in seeds compared to conventional methods utilizing organic solvents. In this work, a novel method where SFE is hyphenated with an evaporative light scattering detector is presented. The method was subsequently applied to determine lipid content in crushed linseed. The new method enables rapid quantification of extracted lipids as well as be ability to continuously monitor the extraction rate in real-time, thus being able to determine the time point of completed extraction. Both the detector and the method was validated. The results show that any of several tested oils can be used to calibrate the detection method for the determination of lipids extraction from linseed. The overall method repeatability and intermediate precision was 2.6% relative standard deviations. The extracted amount was significantly less than that obtained using the standard method of Soxhlet with petroleum ether, 26.0±0.4% (95% CI, n=9) compared to 32.3±1.3% (95% CI, n=3) of extracted amounts. It was found that channeling effects were present, and by either performing sequential repeated extractions with decompression in-between or by using a relatively large vessel a more complete extraction could be obtained. Interestingly, a substantially higher extracted amount (approximately 50%) was obtained compared to both a single extraction by SFE and the Soxhlet method. Therefore, it is recommended that an additional extraction including a rapid decompression in-between should be included in the validation of a method using supercritical fluid extraction, in order to either rule out channeling effects or to acquire a full recovery.
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| 49. |
- Ahlström, Lars-Henric, et al.
(författare)
-
Application of standard addition methodology for the determination of banned azo dyes in different leather types
- 2005
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 552:1-2, s. 76-80
-
Tidskriftsartikel (refereegranskat)abstract
- An analytical procedure based on microwave-assisted extraction (MAE) and standard addition was applied for the determination of banned azo dyes in bovine, sheep, and goat leather. Standard addition at four different concentration levels was performed using azo dyes, dissolved either in methanol or water. All dyes were determined indirectly by measuring their corresponding harmful aromatic amines, formed after reduction by use of sodium dithionite. Comparing found amounts of amines with theoretical target values allowed an assessment of accuracy. The recoveries were also compared with those obtained for non-spiked samples using external standard calibration. The standard addition approaches provided much better accuracy than external standard calibration, with recoveries close to 100% for most amines. Since there was no great difference in recoveries when using methanol or water as solvent, preparation of the dyes in methanol might be preferred because of the faster evaporation of the solvent after spiking. (c) 2005 Elsevier B.V. All rights reserved.
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| 50. |
- Ahmad Tajudin, Asilah, et al.
(författare)
-
MALDI-target integrated platform for affinity-captured protein digestion.
- 2014
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 807:Jan 7, s. 1-8
-
Tidskriftsartikel (refereegranskat)abstract
- To address immunocapture of proteins in large cohorts of clinical samples high throughput sample processing is required. Here a method using the proteomic sample platform, ISET (integrated selective enrichment target) that integrates highly specific immunoaffinity capture of protein biomarker, digestion and sample cleanup with a direct interface to mass spectrometry is presented. The robustness of the on-ISET protein digestion protocol was validated by MALDI MS analysis of model proteins, ranging from 40fmol to 1pmol per nanovial. On-ISET digestion and MALDI MS/MS analysis of immunoaffinity captured disease-associated biomarker PSA (prostate specific antigen) from human seminal plasma are presented.
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