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Search: L773:0003 2670 > (2005-2009)

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1.
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2.
  • Ahlström, Lars-Henric, et al. (author)
  • Application of standard addition methodology for the determination of banned azo dyes in different leather types
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 552:1-2, s. 76-80
  • Journal article (peer-reviewed)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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3.
  • Ali, Hassan, et al. (author)
  • Vibrational spectroscopic characterisation of salmeterol xinafoate polymorphs and a preliminary investigation of their transformation using simultaneous in situ portable Raman spectroscopy and differential scanning calorimetry
  • 2008
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 620:1-2, s. 103-12
  • Journal article (peer-reviewed)abstract
    • Knowledge and control of the polymorphic phases of chemical compounds are important aspects of drug development in the pharmaceutical industry. Salmeterol xinafoate, a long acting beta-adrenergic receptor agonist, exists in two polymorphic Forms, I and II. Raman and near infrared spectra were obtained of these polymorphs at selected wavelengths in the range of 488-1064 nm; significant differences in the Raman and near-infrared spectra were apparent and key spectral marker bands have been identified for the vibrational spectroscopic characterisation of the individual polymorphs which were also characterised with X ray diffractometry. The solid-state transition of salmeterol xinafoate polymorphs was studied using simultaneous in situ portable Raman spectroscopy and differential scanning calorimetry isothermally between transitions. This method assisted in the unambiguous characterisation of the two polymorphic forms by providing a simultaneous probe of both the thermal and vibrational data. The study demonstrates the value of a rapid in situ analysis of a drug polymorph which can be of potential value for at-line in-process control
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4.
  • Ali Malik, Muhammad, et al. (author)
  • Imaging fingerprinting of excitation emission matrices
  • 2009
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 635:2, s. 196-201
  • Journal article (peer-reviewed)abstract
    • The spectral fingerprinting of the excitation emission matrix (EEM) of fluorescent substances is demonstrated using polychromatic light sources and tri-chromatic image detectors. A model of the measured fingerprints explaining their features and classification performance, based on the polychromatic excitation of the indicators is proposed.Substantial amount of spectral information is retained in the fingerprints as corroborated by multivariate analysis and experimental conditions that favor such situation are identified.In average, for five different substances, the model shows a fitting goodness measured by the Pearsons r coefficient and the root mean square deviation of 0.8541 and 0.0247 respectively, while principal component classification patterns satisfactorily compare with the EEM spectroscopy classification and respectively explain 96% and 93% of the information in the fist two principal components.The measurements can be performed using regular computer screens as illumination and web cameras as detectors, which constitute ubiquitous and affordable platforms compatible with distributed evaluations, in contrast to regular instrumentation for EEM measurements.
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5.
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6.
  • Alimelli, Adriano, et al. (author)
  • Fish freshness detection by a computer screen photoassisted based gas sensor array
  • 2007
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 582:2, s. 320-328
  • Journal article (peer-reviewed)abstract
    • In the last years a large number of different measurement methodologies were applied to measure the freshness of fishes. Among them the connection between freshness and headspace composition has been considered by gas chromatographic analysis and from the last two decades by a number of sensors and biosensors aimed at measuring some characteristic indicators (usually amines). More recently also the so-called artificial olfaction systems gathering together many non-specific sensors have shown a certain capability to transduce the global composition of the fish headspace capturing the differences between fresh and spoiled products. One of the main objectives related to the introduction of sensor systems with respect to the analytical methods is the claimed possibility to distribute the freshness control since sensors are expected to be "portable" and "simple". In spite of these objectives, until now sensor systems did not result in any tool that may be broadly distributed. In this paper, we present a chemical sensor array where the optical features of layers of chemicals, sensitive to volatile compounds typical of spoilage processes in fish, are interrogated by a very simple platform based on a computer screen and a web cam. An array of metalloporphyrins is here used to classify fillets of thawed fishes according to their storage days and to monitor the spoilage in filleted anchovies for a time of 8 h. Results indicate a complete identification of the storage days of thawed fillets and a determination of the storage time of anchovies held at room temperature with a root mean square error of validation of about 30 min. The optical system produces a sort of spectral fingerprint containing information about both the absorbance and the emission of the sensitive layer. The system here illustrated, based on computer peripherals, can be easily scaled to any device endowed with a programmable screen and a camera such as cellular phones offering for the first time the possibility to fulfil the sensor expectation of diffused and efficient analytical capabilities. © 2006 Elsevier B.V. All rights reserved.
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7.
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8.
  • Astuti, Yeni, et al. (author)
  • Direct spectroelectrochemistry of peroxidases immobilised on mesoporous metal oxide electrodes : Towards reagentless hydrogen peroxide sensing
  • 2009
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 648:1, s. 2-6
  • Journal article (peer-reviewed)abstract
    • In this paper, we employ two peroxidases (horseradish peroxidase, HRP and cytochrome c peroxidase, CcP) to demonstrate their ability to retain their redox and biological functions after their immobilisation on mesoporous TiO2 and SnO2 electrodes. We will also demonstrate the use of HRP immobilised on the metal oxide electrodes for the development of reagentless optical and electrochemical biosensors for the detection of hydrogen peroxide (H2O2) with low detection limit of 0.04 and 1 mu M, respectively. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
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9.
  • Beni, Valerio, et al. (author)
  • Development of a portable electroanalytical system for the stripping voltammetry of metals : Determination of copper in acetic acid soil extracts
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 552:1-2, s. 190-200
  • Journal article (peer-reviewed)abstract
    • The development, characterisation and evaluation of a prototype portable electrochemical trace metal analyser are presented. The instrumentis a battery-powered microcontroller-based potentiostat, which implements anodic stripping voltammetry (ASV) at suitable sensor electrodes.It is capable of operating away from the laboratory, in the absence of an external power source and is usable by low-skilled personnel. Thedistinguishing feature of the instrument is its custom software, which enables sample pre-screening, data processing and sample dilution andstandard additions calculations to be carried out. The instrument has been evaluated by application of a methodology for the detection ofcopper in acetic acid soil extracts, both in the laboratory and in the field. Underpotential deposition staircase anodic stripping voltammetry(UPD-SCASV) of the copper at gold disk electrodes was used as a test method. There was good agreement between the instrument resultsand those from laboratory-based reference analytical methods for analyses carried out both in the laboratory and in the field.
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10.
  • Bergström, Staffan, et al. (author)
  • Extracting syringe for extraction of phthalate esters in aqueous environmental samples
  • 2007
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 594:2, s. 240-247
  • Journal article (peer-reviewed)abstract
    • The use of the extracting syringe (ESy), a fully automated membrane-based extraction technique, for analysis of phthalate esters in complex aqueous samples has been investigated. The ESy, working as an autosampler that combines the extraction process and injection into the gas chromatograph (GC) in one single step, is placed on top of the GC equipped with a flame ionisation detector. The aqueous samples are loaded in a tray and automatically extracted by employing microporous membrane liquid-liquid extraction principle. After the extraction, the extract is directly injected into the GC's programmable temperature vaporisation injector. Six different phthalate esters were used as model compounds. Four extraction solvents were tested and the addition of sample organic modifier was examined. Toluene was the optimal solvent to use for extraction. Due to the large variation in polarity of phthalate esters, 50% methanol as organic modifier had to be added to the samples so as to extract the most nonpolar phthalate esters; di-2-ethylhexylphthalate and di-n-octylphthalate, whereas the other four relatively polar phthalate esters were extracted from unmodified samples. No significant difference between extraction of river water, leachate water from a landfill and reagent water was noted, except for minor deviations. The extraction time was 20 min for extraction of a 1-mL sample, resulting in a good linearity for all aqueous media investigated, good enrichment factors (54-110 folds) and low LOD values (0.2-10 ng mL(-1)) and relative standard deviation (%R.S.D.; 0.9-3.7%).
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11.
  • Carlsson, Jenny, 1977-, et al. (author)
  • Biosensor discrimination of meat juice from various animals using a lectin panel and ellipsometry
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 547:2, s. 229-236
  • Journal article (peer-reviewed)abstract
    • In this work, simple microcontact printed gold-wafers were used to make a lectin panel for investigation and discrimination of different meat juices from fresh meat of cattle, chicken, pig, cod, turkey and lamb. Seven different lectins were thus attached to gold surfaces using the streptavidin–biotin method. Lectins recognize and bind specifically to carbohydrate structures present on different proteins. The biorecognition was evaluated with null ellipsometry and the data obtained was related to an internal standard of lactoferrin. The data was evaluated with multivariate data analysis techniques to identify possible discrimination or grouping of data. Scanning ellipsometry was used for visualization of the binding pattern of the lectins and the meat juice proteins. The two-dimensional images obtained could be used to visualize the protein distribution, furthermore, to exclude anomalies. The results showed that the different meat juices from the six different species: cattle, chicken, pig, cod, turkey and lamb could be discriminated from each other. The results showed to be more repetitive for the mammalian meat juices. Using a simple model based on an artificial neuronal net, it was also possible to classify meat juices from the mammals investigated.
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12.
  • Carlsson, Jenny, 1977-, et al. (author)
  • Investigation of sera from various species by using lectin affinity arrays and scanning ellipsometry
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 530:2, s. 167-171
  • Journal article (peer-reviewed)abstract
    • Serum proteins of different species and of different human blood groups exhibit various protein glycosylation patterns. Sera from human, pig, sheep and guinea pig have been applied to a panel of eight different lectins immobilized on a gold wafer. The biorecognition has been evaluated with scanning ellipsometry and the two-dimensional matrices obtained have been treated with image analysis and MVDA for evaluation. The results showed a clear difference in protein binding pattern between the different species and thereby separation of the different sera could be made. Dendograms indicate that human and pig sera are the most related of the four different sera investigated.
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13.
  • Chen, Guohe, et al. (author)
  • In-field determination of nanomolar nitrite in seawater using a sequential injection technique combined with solid phase enrichment and colorimetric detection
  • 2008
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 620:1-2, s. 82-88
  • Journal article (peer-reviewed)abstract
    • A novel sequential injection method for the determination of nitrite at nanomolar level in seawater samples has been developed. The pink azo compound was formed based on the Griess reaction and quantitatively adsorbed onto a Sep-Pak C18 cartridge. The enriched azo compound was rinsed with water and ethanol (28%, v/v) in turn, and then eluted with an eluent containing 26.6% (v/v) ethanol and 0.108mol L-1 H2SO4. Finally the azo compound was measured using a spectrophotometer at 543 nm. Under the optimized conditions, the linear calibration ranges were 0.71-42.9 nmol L-1 for a 150-mL sample and 35.7-429 nmol L-1 for a 15-mL sample. The relative standard deviation of 8 measurements was 1.44% for 14.3 nmol L-1 nitrite. For the 150 mL sample, the detection limit was estimated to be 0.1 nmol L-1. The throughput of the method was about 4 samples per hour. The proposed method has been successfully applied to the in-field determination of nanomolar concentrations of nitrite in seawater. (c) 2008 Elsevier B.V. All rights reserved.
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14.
  • Cheung, Kwan Yee, et al. (author)
  • Reusable optical bioassay platform with permeability-controlled hydrogel pads for selective saccharide detection
  • 2008
  • In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 607:2, s. 204-210
  • Journal article (peer-reviewed)abstract
    • A reusable optical bioassay platform using permeability-controlled hydrogel pads for selective saccharide detection has been developed. An optical glucose detection assay based on fluorescence resonance energy transfer (FRET) between dye-labeled dextran and Concanavalin A (ConA) was incorporated into hydrogel pads by entrapment. The hydrogel pads are constructed from hemispherical hydrogel attached onto hydrophobic surfaces of a microtiter plate. The resulted hemispherical hydrogel pads entrapping the sensing biological materials were further surface coated with polyelectrolyte multilayers through a Layer-by-Layer (LbL) self-assembly process to create a permeability-controlled membrane with nanometer thickness. The selective permeable LbL film deposited on the hydrogel surface allows small molecular weight analytes to diffuse into the hydrogel pads while the large molecular weight sensing biological molecules are immobilized. An encapsulation efficiency of 75% for the ConA/Dextran complex within the coated hydrogel pads was achieved and no significant leakage of the complex was observed. Glucose calibration curve with linear range from 0 to 10 mM glucose was obtained. Selective permeability of the hydrogel pads has been demonstrated by measurement of saccharides with various molecular weights. The LbL hydrogel pads could selectively detect monosaccharides (glucose, MW = 180) and disaccharides (sucrose, MW = 342) while polysaccharides (dextran, MW ∼ 70 kDa) cannot diffuse through the LbL layer and are excluded. LbL hydrogel pads allow regeneration of the FRET system with good signal reproducibility of more than 90% to construct a reusable and reagentless optical bioassay platform.
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15.
  • Cohen, Arieh, et al. (author)
  • Investigation of the enzyme Bacillus agaradhaerens Cel 5a as an analytical tool in mass spectral characterisation of methylcelluloses
  • 2006
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 561:1-2, s. 16-24
  • Journal article (peer-reviewed)abstract
    • Two methylcelluloses (MC) were investigated by partial hydrolysis followed by direct infusion electrospray ionisation mass spectrometry (ESI-MS). Partial hydrolysis was achieved either enzymatically or by acid hydrolysis. Enzyme hydrolysis was performed using the endoglucanase Bacillus agaradhaerens Cel 5a. Three different hydrolysis buffer solutions were investigated in order to deter-mine which was most compatible with the subsequent MS analysis. ESI-MS experiments showed that when using enzymatic hydrolysis as an analytical tool for characterisation of modified cellulose one has to be watchful for the investigated polymer to have a sufficient amount of available cleavage sites in order to ensure that the original ends of the polymer do not influence the results. MS2 experiments confirmed that the detected products originated from methylcellulose and provided structural information on the investigated products. MS data proved that B. agaradhaerens Cel 5a is able to cleave beta 1 -> 4 glycosidic linkages adjacent to a permethylated glucosyl unit. MS2 data showed that methylation on the C-2 and C-6 hydroxyl groups of the glucosyl unit on the non-reducing side of the cleavage site hindered the enzyme. (c) 2006 Elsevier B.V. All rights reserved.
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16.
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17.
  • de Boer, J., et al. (author)
  • United Nations Environment Programme Capacity Building Pilot Project : training and interlaboratory study on persistent organic pollutant analysis under the Stockholm Convention
  • 2008
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 617:1-2, s. 208-215
  • Journal article (peer-reviewed)abstract
    • Within the framework of a United Nations Environment Programme (UNEP) Capacity Building Project for training of laboratory staff in developing countries on persistent organic pollutant (POP) analysis, an interlaboratory study was organised following an initial evaluation of the performance of laboratories (reality check) and a series of training sessions. The target compounds were polychlorinated biphenyls (PCB) and organochlorine pesticides (OCP). Seven laboratories from five countries (Ecuador, Uruguay, Kenya, Moldova, and Fiji) participated. Most of the laboratories had no experience in determining PCBs. Although chromatograms improved considerably after the training and installation of new gas chromatographic (GC) columns at participating laboratories, the level of performance in the interlaboratory study was essentially on par with the moderate performance level achieved by European POP laboratories in the 1980s. Only some individual results were within +/-20% of the target values. The relative standard deviations (R.S.D.s) in POP concentrations determined by laboratories in a sediment sample were >200% in a number of cases. The results for a certified herring sample were better with at least some R.S.D. values below 50% and most below 100%. Clean up was as one of the main sources of error. After inspection it was ascertained that training of laboratory staff and investments in simple consumables such as glassware and GC columns would help to improve the quality of the analysis more than major investments in expensive instrumentation. Creating an effective network of POP laboratories at different continents together with a series of interlaboratory studies and workshops is suggested to improve the measurements of POPs in these countries.
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18.
  • Degueldre, C., et al. (author)
  • Gold colloid analysis by inductively coupled plasma-mass spectrometry in a single particle mode
  • 2006
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 555:2, s. 263-268
  • Journal article (peer-reviewed)abstract
    • Analysis in a single particle mode of gold colloids in water has been performed by inductively coupled plasma-mass spectrometry (ICP-MS). The signal induced by the flash of ions due to the ionization of a colloid in the plasma torch can be measured for the ions (197)An(+) by the mass spectrometer without interferences. The intensity of the MS signal is recorded in time scan. The recorded peak distributions were analysed as a function of the colloid size for five monodisperse colloids (80-250 nm). This study describes the experimental conditions to analyse gold colloids in a single particle mode. The size detection limit is around 25 nm corresponding to 0.15 fg colloids and one particle per ml may be detected during a 1 min time scan within standard procedure.
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19.
  • Dilgin, Y, et al. (author)
  • Photoelectrochemical investigation of methylene blue immobilised on zirconium phosphate modified carbon paste electrode in flow injection system
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 542:2, s. 162-168
  • Journal article (peer-reviewed)abstract
    • The adsorption of methylene blue (MB) onto zirconium phosphate (ZrP) was studied and the adsorption capacity value and isotherms were determined. The adsorption capacity of ZrP was increased after being exposed to gas phase n-butyl amine. The adsorbed MB on ZrP was used as a modifier material in carbon paste electrode (MCPE), which in turn was used in voltammetric investigations and flow injection (FI) amperometric determination of ascorbic acid (AA). A quasi-reversible electrode reaction of adsorbed MB was exhibited. A home made flow-through electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed and used for amperometric FI studies. The photoamperometric-FI conditions were optimised as 1.5 mL min(-1) flow rate, a 25 cm transmission tubing length, a 100 mu L injection volume, and a constant applied potential of +100 mV versus SCE. The calibration curve for AA was linear over the concentration range from 1.0 x 10(-6) to 4.0 x 10(-5) M. The relative standard deviation of four replicate injections of 3.0 x 10(-5) M AA was 1.2 %. The results obtained for AA determination in pharmaceutical products are in good agreement with those obtained using the procedure involving the reaction between triiodide and AA. (c) 2005 Elsevier B.V. All rights reserved.
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20.
  • Dock, Eva, et al. (author)
  • A steady-state and flow-through cell for screen-printed eight-electrode arrays
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 531:2, s. 165-172
  • Journal article (peer-reviewed)abstract
    • An electrochemical cell has been developed enabling amperometric steady-state- and flow-injection measurements with screen-printed arrays consisting of eight working electrodes (circle divide = 1 mm) arranged radially around a printed Ag/AgCl reference electrode in the centre. The cell contained a rotator, providing similar hydrodynamics over all the working electrodes in the array, which was manually centered under the rotator. The reproducibility of steady-state measurements with eight-electrode platinum or gold arrays in this cell was studied by measuring and comparing currents from ferricyanide reduction at each electrode in the array. It was found that the relative standard deviation (R.S.D.) for the currents at different electrodes on one array was below 5%. Similar R.S.D. was found if measurements were compared between several arrays. This indicates that manual insertion/positioning of the eight-electrode array in the cell and hydrodynamics at the electrodes provided measurement reproducibility similar to the reproducibility of manufacturing eight-electrode platinum or gold arrays by screen-printing. A comparative study was performed between screen-printed and through mask sprayed carbon arrays. It was found that the reproducibility of the sprayed arrays was similar to that of the platinum or gold screen-printed arrays, with R.S.D. values below 6% regarding the variation between electrodes within the same array and the variation between different arrays. To enable flow-injection measurements, a tube (0.4 mm inner diameter) was inserted into a hole drilled through the centre of the steady-state cell rotator. This construction made it possible to inject the solution into the cell through the tube (not rotating), while the rotator was spinning over the eight-electrode array. It was found that this combination of flow-injection and mixing by a rotator provided a uniform current response over the array electrodes and that, at optimum conditions, the R.S.D. values between the eight electrodes in the array were nearly the same as in case of the steady-state measurements, i.e., below 5%. (C) 2004 Elsevier B.V. All rights reserved.
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21.
  • Drapala, Anna, et al. (author)
  • Peptides analysis in blood plasma using on-line system of supported liquid membrane and high-performance liquid chromatography
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 553:1-2, s. 9-14
  • Journal article (peer-reviewed)abstract
    • The potential of using supported liquid membrane (SLM) technique, combined with reversed-phase high-performance liquid chromatography (RP-HPLC) has been investigated for the determination of peptides in human blood plasma. The peptides studied were (DL)Leu(DL)Phe, MetLeuPhe, GlyLeuTyr and ValGluProlleProTyr. The carrier (Aliquat 336) was incorporated in membrane phase in order to facilitate the transport of investigated peptides. After extraction, the analyte-enriched acceptor phase was directly injected into an HPLC system for analysis. With SLM, high selectivity and efficiency were achieved for extraction of peptides in aqueous solutions. Lower extraction efficiency was obtained in plasma sample. The limiting factors were the presence of salts and proteins in blood plasma. The necessary of ultrafiltration application before the SLM was required in order to improve its stability. The minimum quantifiable concentration was 90-130 ng/ml of the investigated peptides based on 0.5 ml plasma. The standard curve was linear over the concentration range of 0.05-10 mu g/ml. (c) 2005 Elsevier B.V. All rights reserved.
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22.
  • Dziarkowska, Katarzyna, et al. (author)
  • Single hollow fiber SLM extraction of polyamines followed by tosyl chloride derivatization and HPLC determination
  • 2008
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 606:2, s. 184-193
  • Journal article (peer-reviewed)abstract
    • Determination of polyamines in biological fluids possesses medical diagnostic relevance. Despite the vast panel of analytical methods developed for polyamines they are not applied in routine clinical usage, mainly due to the time and labor consuming sample preparation step and complicated derivatization. procedures. Thus, new simpler methods are needed. This paper describes a single hollow fiber SLM extraction method of polyarnines followed by simple pre-column derivatization with tosyl chloride and HPLC-UV analysis. The influence of different parameters such as the extraction time, organic phase composition, acceptor pH, donor pH, acceptor volume, donor volume and stirring speed on the transport parameters and enrichment was studied and discussed. The optimized method was applied to real matrices such as urine and plasma.
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23.
  • Emmer, Åsa, et al. (author)
  • Enzymatic protein digest in chip-based nanovials with immobilized proteolytic enzymes
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 542:2, s. 137-143
  • Journal article (peer-reviewed)abstract
    • In the present work, protein digest reactions in silicon-based microchips, coated with immobilized proteolytic enzymes, have been carried out. The performance of such vials, modified with trypsin or chymotrypsin, was tested with myoglobin as a substrate. Capillary electrophoresis and matrix-assisted laser desorption/ionization mass spectrometry were utilized for analysis of the digests, and the influence of different instrumentation setups. immobilization procedures and reaction conditions are discussed.
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24.
  • Farajzadeh, Mir Ali, et al. (author)
  • Dispersive liquid-liquid microextraction followed by high-performance liquid chromatography-diode array detection as an efficient and sensitive technique for determination of antioxidants
  • 2007
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 591:1, s. 69-79
  • Journal article (peer-reviewed)abstract
    • Dispersive liquid-liquid microextraction (DLLME) and high performance liquid chromatography-diode array detection (HPLC-DAD) was presented for extraction and determination of Irganox 1010, Irganox 1076 and Irgafos 168 (antioxidants) in aqueous samples. Carbon tetrachloride at microliter volume level and acetonitrile were used as extraction and dispersive solvents, respectively. The main advantages of method are high speed, high enrichment factor, high recovery, good repeatability and extraction solvent volume at mu L level. Limit of detection for analytes is between 3 and 7 ng mL(-1). One variable at a time optimization and response surface modeling were used to obtain optimum conditions for microextraction procedure and nearly same experimental conditions were obtained using both optimization methods. Recoveries in the ranges 78-86% and 84-110% were obtained by one variable at a time and response surface modeling, respectively. Using tap water and packed water as matrices do not show any detrimental effect on the extraction recoveries and enrichment factors of analytes. (C) 2007 Elsevier B.V. All rights reserved.
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25.
  • Farajzadeh, Mir Ali, et al. (author)
  • Solvent exchange using hollow fiber prior to separation and determination of some antioxidants by high performance liquid chromatography
  • 2007
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 594:1, s. 75-80
  • Journal article (peer-reviewed)abstract
    • This study presents a simple and rapid solvent exchange procedure using a hollow fiber. Antioxidants (Irganox 1010, Irganox 1076 and Irgafos 168) and solvents such as tetrahydrofuran (THF), carbon tetrachloride and toluene were selected as model compounds and sample solvents, respectively. After injection of the sample solution into the hollow fiber and solvent evaporation, the precipitated analytes in lumen and pores of the fiber were washed with methanol (the mobile phase for separation and determination by HPLC-diode array detection) and good chromatographic peaks were obtained. The effect of different parameters such as fiber length, volumes of sample and washing solvents were investigated and the optimum conditions were selected. The repeatability of the method was tested and it was found that the relative standard deviation (R.S.D.) was less than 10% for all analytes. Also enrichment factors of 3.03, 2.21 and 1.19 times were obtained for Irganox 1010, Irganox 1076 and Irgafos 168, respectively, when 200 mu L sample and 50 mu L methanol (washing solvent) were used. (c) 2007 Elsevier BX All rights reserved.
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26.
  • Filippini, Daniel, et al. (author)
  • Computer screen photo-excited surface plasmon resonance imaging
  • 2008
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 625:2, s. 207-214
  • Journal article (peer-reviewed)abstract
    • Angle and spectra resolved surface plasmon resonance (SPR) images of gold and silver thin films with protein deposits is demonstrated using a regular computer screen as light source and a web camera as detector. The screen provides multiple-angle illumination, p-polarized light and controlled spectral radiances to excite surface plasmons in a Kretchmann configuration. A model of the SPR reflectances incorporating the particularities of the source and detector explain the observed signals and the generation of distinctive SPR landscapes is demonstrated. The sensitivity and resolution of the method, determined in air and solution, are 0.145 nm pixel-1, 0.523 nm, 5.13 × 10-3 RIU degree-1 and 6.014 × 10-4 RIU, respectively, encouraging results at this proof of concept stage and considering the ubiquity of the instrumentation. © 2008 Elsevier B.V. All rights reserved.
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29.
  • Geladi, Paul, et al. (author)
  • Complex numbers in chemometrics : Examples from multivariate impedance measurements on lipid monolayers
  • 2007
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 595:1-2, s. 152-9
  • Journal article (peer-reviewed)abstract
    • Electrical impedance gives multivariate complex number data as results. Two examples of multivariate electrical impedance data measured on lipid monolayers in different solutions give rise to matrices (16 × 50 and 38 × 50) of complex numbers. Multivariate data analysis by principal component analysis (PCA) or singular value decomposition (SVD) can be used for complex data and the necessary equations are given. The scores and loadings obtained are vectors of complex numbers. It is shown that the complex number PCA and SVD are better at concentrating information in a few components than the naïve juxtaposition method and that Argand diagrams can replace score and loading plots. Different concentrations of Magainin and Gramicidin A give different responses and also the role of the electrolyte medium can be studied. An interaction of Gramicidin A in the solution with the monolayer over time can be observed.
  •  
30.
  • Geladi, Paul (author)
  • Maize kernel hardness classification by near infrared (NIR) hyperspectral imaging and multivariate data analysis
  • 2009
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 653, s. 121-130
  • Journal article (peer-reviewed)abstract
    • The use of near infrared (NIR) hyperspectral imaging and hyperspectral image analysis for distinguishing between hard, intermediate and soft maize kernels from inbred lines was evaluated. NIR hyperspectral images of two sets (12 and 24 kernels) of whole maize kernels were acquired using a Spectral Dimensions MatrixNIR camera with a spectral range of 960-1662 nm and a sisuChema SWIR (short wave infrared) hyperspectral pushbroom imaging system with a spectral range of 1000-2498 nm. Exploratory principal component analysis (PCA) was used on absorbance images to remove background, bad pixels and shading. On the cleaned images. PCA could be used effectively to find histological classes including glassy (hard) and floury (soft) endosperm. PCA illustrated a distinct difference between glassy and floury endosperm along principal component (PC) three on the MatrixNIR and PC two on the sisuChema with two distinguishable clusters. Subsequently partial least squares discriminant analysis (PLS-DA) was applied to build a classification model. The PLS-DA model from the MatrixNIR image (12 kernels) resulted in root mean square error of prediction (RMSEP) value of 0.18. This was repeated on the MatrixNIR image of the 24 kernels which resulted in RMSEP of 0.18. The sisuChema image yielded RMSEP value of 0.29. The reproducible results obtained with the different data sets indicate that the method proposed in this paper has a real potential for future classification uses. (c) 2009 Elsevier B.V. All rights reserved.
  •  
31.
  • Guerreiroa, Antonio, et al. (author)
  • Preliminary evaluation of new polymer matrix for solid-phase extraction of nonylphenol from water samples
  • 2008
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 612:1, s. 99-104
  • Journal article (peer-reviewed)abstract
    • Molecularly imprinted (MIP) and blank polymers with affinity for nonylphenol were designed using computational modelling. Chromatographic tests demonstrated higher affinity of imprinted polymers towards the template nonylphenol as compared with blank polymers. The performance of both polymers in solid-phase extraction was however very similar. Both blank and imprinted polymers appeared to be suitable for the removal and pre-concentration of nonylphenol from contaminated water samples with 99% efficiency of the recovery. The commercial resins PH(EC) (Biotage) and C18 (Varian) tested in the same conditions used for comparative purposes had recovery rate < 84%. The polymer capacity for nonylphenol was 231 mg g(-1) for blank and 228 mg g(-1) for MIR The synthesised materials can have significance for sample pre- concentration and environmental analysis of this class of compounds.
  •  
32.
  • Hakonen, Aron, 1970, et al. (author)
  • A high-precision ratiometric fluorosensor for pH: Implementing time-dependent non-linear calibration protocols for drift compensation
  • 2007
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 606:1, s. 63-71
  • Journal article (peer-reviewed)abstract
    • We present a versatile time-dependent non-linear calibration protocol for optical sensors, implemented on the pH sensitive ratiometric fluorophore 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) immobilized in ethyl-cellulose. The calibration protocol individually compensated for the progressive drift of calibration parameters, whereby sensor precision and accuracy, as well as applicable lifetime were improved. A severely reduced photoacidity was observed for the immobilized fluorophore, for which excited state dynamics was characterized and benefited from during measurements. Due to the significantly reduced photoacidity of HPTS immobilized in the ethyl-cellulose sensing membrane, a dual excitation/dual emission (F1, ex/em: 405/440 nm and F2, ex/em: 465/510 nm) ratiometric (RF1,F2 = F1/F2) sensing scheme could be used to amplify sensor response. The signal to noise (S/N) ratio was enhanced by 400% utilizing the dual excitation/dual emission ratiometric sensing scheme, rather than the more commonly used protocol of dual excitation/single emission for HPTS fluorescence. Apparent pKa of the fluorophore ranged from 6.74 to 8.50, mainly determined by the immobilization procedure. The repeatability (IUPAC, pooled standard deviation) over three pH values (6.986, 7.702 and 7.828) was 0.0044 pH units for the optical sensor, compared to 0.0046 for the electrode used for standardization. Sensor analytical characteristics were thereby in principle limited by the performance of the standardization procedure.
  •  
33.
  • Hartmann, Michael, et al. (author)
  • Increasing robustness and sensitivity of protein microarrays through microagitation and automation
  • 2006
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 564:1, s. 66-73
  • Journal article (peer-reviewed)abstract
    • Assay systems that employ protein microarrays for the analysis of complex samples are powerful tools to generate a high amount of data from a limiting amount of sample. Due to miniaturization, these systems are susceptible to fluctuations during signal generation and the use of uniform conditions for sample incubation and during the assay procedure is required to get reproducible results. Diffusion limits may prevent constant conditions on all parts of the array and can lead to the decease of the sensitivity of the array. Therefore, we set-up an automated assay system integrating a novel microagitation device using surface acoustic wave (SAW) technology. Multiplexed assays for the detection of autoantibodies from human serum and sandwich immunoassay for the detection of matrix metalloproteases (MMPs) were used to evaluate the system. Diffusion-rate limited solid phase reactions were enhanced by microagitation using the SAW technology resulting in up to three-fold higher signals.
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34.
  • Hou, Xiaolin, et al. (author)
  • A review on speciation of iodine-129 in the environmental and biological samples
  • 2009
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 632:2, s. 181-196
  • Research review (peer-reviewed)abstract
    • As a long-lived beta-emitting radioisotope of iodine, I-129 is produced both naturally and as a result of human nuclear activities. At present time, the main part of I-129 in the environment originates from the human nuclear activity, especially the releases from the spent nuclear fuel reprocessing plants, the I-129/I-127 ratios have being reached to values of 10(-10) to 10(-4) in the environment from 10(-12) in the pre-nuclear era. In this article, we review the occurrence, sources, inventory, and concentration level of I-129 in environment and the method for speciation analysis of I-129 in the environment. Measurement techniques for the determination of I-129 are presented and compared. An overview of applications of I-129 speciation in various scientific disciplines such as radiation protection, waste depository, and environmental sciences is given. In addition, the bioavailability and radiation toxicity (close to thyroid) of I-129 are discussed.
  •  
35.
  • Josefsson, Sarah, et al. (author)
  • Evaluation of PLE exhaustiveness for the extraction of PCBs from sediments and the influence of sediment characteristics
  • 2006
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 560:1-2, s. 94-102
  • Journal article (peer-reviewed)abstract
    • Pressurized liquid extractions were performed on eight sediments in order to investigate if a modified US EPA method (100 degrees C, 100 bar, n-heptane/acetone (1:1), 2 x 5 min) provided exhaustive extractions of polychlorinated biphenyls (PCBs) from sediment, and to study if the extractability of PCBs from the different sediments was affected by characteristics of the sediment. The recovery from the eight native sediments, contaminated in nature, was between 96.4% and 98.9%, as an average of the recoveries from 10 PCB congeners. Hundred percent recovery was defined as the sum of two consecutive extractions (2 x 5 min each) at the stated conditions. The recoveries of the individual congeners were above 94%, except for one congener in one sediment, which had a recovery of 92%. When the recoveries and different characteristics of the sediments were compared, no correlation appeared between recoveries and sediment PCB concentration, total organic carbon (TOC), soot carbon (SC) or amorphous carbon (AC). The fact that carbon did not influence the extractions was somewhat surprising, since previous experiments have indicated a connection. Instead, statistically significant (p < 0.05) correlations were observed for water content and carbon/nitrogen (C/N) ratio. The decrease in recoveries with decreased water content was attributed to less access of the solvent to the analytes due to less matrix swelling. The lowered recoveries with increased C/N ratio can indicate that a difference in structure of the organic matter exists, which influences the binding strength between the analytes and the matrix. The difference in structure can possibly be explained by different origin of the organic matter or by aging effects. Overall the method was found to be exhaustive and the excellent recoveries show that sediment characteristics do not influence the extractions markedly.
  •  
36.
  • Jönsson, Sofie, et al. (author)
  • Multivariate characterisation and quantitative structure-property relationship modelling of nitroaromatic compounds
  • 2008
  • In: Analytica Chimica Acta. - Amsterdam : Elsevier. - 0003-2670 .- 1873-4324. ; 621:2, s. 155-162
  • Journal article (peer-reviewed)abstract
    • A multivariate model to characterise nitroaromatics and related compounds based on molecular descriptors was calculated. Descriptors were collected from literature and through empirical, semi-empirical and density functional theory-based calculations. Principal components were used to describe the distribution of the compounds in a multidimensional space. Four components described 76% of the variation in the dataset. PC1 separated the compounds due to molecular weight, PC2 separated the different isomers, PC3 arranged the compounds according to different functional groups such as nitrobenzoic acids, nitrobenzenes, nitrotoluenes and nitroesters and PC4 differentiated the compounds containing chlorine from other compounds. Quantitative structure-property relationship models were calculated using partial least squares (PLS) projection to latent structures to predict gas chromatographic (GC) retention times and the distribution between the water phase and air using solid-phase microextraction (SPME). GC retention time was found to be dependent on the presence of polar amine groups, electronic descriptors including highest occupied molecular orbital, dipole moments and the melting point. The model of GC retention time was good, but the precision was not precise enough for practical use. An important environmental parameter was measured using SPME, the distribution between headspace (air) and the water phase. This parameter was mainly dependent on Henry's law constant, vapour pressure, logP, content of hydroxyl groups and atmospheric OH rate constant. The predictive capacity of the model substantially improved when recalculating a model using these five descriptors only.
  •  
37.
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38.
  • Kubán, P, et al. (author)
  • Flow/sequential injection sample treatment coupled to capillary electrophoresis. A review
  • 2009
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 648, s. 129-145
  • Journal article (peer-reviewed)abstract
    • Various flow sample handling approaches coupled to capillary electrophoresis (CE) are reviewed, covering the research in this field in the 12 years since the milestone year of 1997, when practical interfaces to on-line couple flow injection (FI) and capillary electrophoresis were first developed independently by two research groups. Some previous attempts are also presented. Since 1997 a plethora of ingenious coupled systems have been developed. Although several reviews are available on various aspects of the topic, we have opted for a comprehensive overview of all FI-CE systems, as well as related and similar systems. This coupling has thus also led to the development of systems based on hybrids between the classical and microchip approaches. Truly microchip FI-CE systems are also included in this review. The developed systems have been used for various sample treatments, including on-line membrane-assisted sample treatment, column-based preconcentration, on-line derivatization and monitoring, to name just a few. The utility of coupling flow sampling to CE has been demonstrated in various practical applications that are discussed in detail. The current state-of-the-art and foreseeable future developments are also discussed.
  •  
39.
  • Kumar, MA, et al. (author)
  • Automated flow enzyme-linked immunosorbent assay (ELISA) system for analysis of methyl parathion
  • 2006
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 560:1-2, s. 30-34
  • Journal article (peer-reviewed)abstract
    • sensitive detection of pesticides is of utmost importance in environment pesticides in agricultural and environmental samples wherein antibodies are employed against the target molecules. Accurate diagnosis depends on the affinity and specificity of the antibody preparation used, and high affinity antibodies are essential for the detection of very small amounts of pesticides. Enzyme linked immuno sorbent assay (ELISA) coupled with flow injection analysis (FIA) technique provides a very high sensitivity with high throughput of analyses. Automation of this analysis scheme ensures precise detection with high accuracy. The present development aims at providing a user-friendly system for achieving this objective. It employs a 8952 microcontroller for precise flow of reagents, samples, substrate and conjugates used for analysis to be passed through an immobilized antibody column at predetermined time. With the sequence and flow control of buffers used, it also provides the option for reuse of the immobilized antibody column. The system is flexible to accommodate multiple sequences up to a maximum of 99 steps. It is customizable for different flow ELISA applications. It can control up to eight solenoid valves (dc 24 V) and two peristaltic pumps and has one 12 bit analog channel for data acquisition. With the serial interface port, the system provides convenient means for data acquisition into the computer. The system has been successfully tested for immuno analysis of organophosphorous pesticide methyl parathion. (c) 2005 Elsevier B.V. All rights reserved.
  •  
40.
  • Kylander, Malin E., et al. (author)
  • A rapid and reliable method for Pb isotopic analysis of peat and lichens by laser ablation-quadrupole-inductively coupled plasma-mass spectrometry for biomonitoring and sample screening
  • 2007
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 582:1, s. 116-124
  • Journal article (pop. science, debate, etc.)abstract
    • An analytical protocol for rapid and reliable laser ablation-quadrupole (LA-Q)- and multi-collector (MC-) inductively coupled plasma-mass spectrometry (ICP-MS) analysis of Pb isotope ratios (207Pb/206Pb and 208Pb/206Pb) in peats and lichens is developed. This technique is applicable to source tracing atmospheric Pb deposition in biomonitoring studies and sample screening. Reference materials and environmental samples were dry ashed and pressed into pellets for introduction by laser ablation. No binder was used to reduce contamination. LA-MC-ICP-MS internal and external precisions were <1.1% and <0.3%, respectively, on both 207Pb/206Pb and 208Pb/206Pb ratios. LA-Q-ICP-MS internal precisions on 207Pb/206Pb and 208Pb/206Pb ratios were lower with values for the different sample sets <14.3% while external precisions were <2.9%. The level of external precision acquired in this study is high enough to distinguish between most modern Pb sources. LA-MC-ICP-MS measurements differed from thermal ionisation mass spectrometry (TIMS) values by 1% or less while the accuracy obtained using LA-Q-ICP-MS compared to solution MC-ICP-MS was 3.1% or better using a run bracketing (RB) mass bias correction method. Sample heterogeneity and detector switching when measuring 208Pb by Q-ICP-MS are identified as sources of reduced analytical performance.
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41.
  • Labib, Mahmoud, et al. (author)
  • A capacitive immunosensor for detection of cholera toxin
  • 2009
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 634:2, s. 255-261
  • Journal article (peer-reviewed)abstract
    • Contamination of food with biological toxins aswell as their potential use asweapons of mass destruction has created an urge for rapid and cost effective analytical techniques capable of detecting trace amounts of these toxins. This paper describes the development of a sensitive method for detection of cholera toxin (CT) using a flow-injection capacitive immunosensor based on self-assembled monolayers. The sensing surface consists of monoclonal antibodies against the B subunit of CT (anti-CT), immobilized on a gold transducer. Experimental results showthat the immunosensor responded linearly to CT concentrations in the range from 1.0×10−13 to 1.0×10−10 M under optimized conditions. The limit of detection (LOD) was 1.0×10−14 M. Two more analytical methods were employed for detection of CT using the same antibody namely, sandwich ELISA and surface plasmon resonance (SPR)-based immunosensor. The former had an LOD of 1.2×10−12 M and a working range from3.7×10−11 to 2.9×10−10 M whereas, the latter had an LOD of 1.0×10−11 M and a linearity ranging from 1.0×10−9 to 1.0×10−6 M. These results demonstrate that the developed capacitive immunosensor system has a higher sensitivity than the other two techniques. The binding affinity of CT to the immobilized anti-CT was determined using the SPR-based immunosensor and an association constant (KA) of 1.4×109 M−1 was estimated.
  •  
42.
  • Larsson, Tobias, 1974, et al. (author)
  • Correction of inner-filter effect in fluorescence excitation-emission matrix spectrometry using Raman scatter.
  • 2007
  • In: Analytica chimica acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 583:2, s. 357-63
  • Journal article (peer-reviewed)abstract
    • Fluorescence excitation-emission matrix (EEM) spectroscopy is a useful tool for interpretation of fluorescence information from natural water samples. One of the major problems with this technique is the inner-filter effect (IFE), i.e. absorption of light at both the excitation and emission wavelengths. The common solutions are to either dilute the sample or apply some form of mathematical correction, most often based on the measured absorbance of the sample. Since dilution is not always possible, e.g. in on-line or in situ EEM recordings, and corrections based on absorbance are hampered primarily by the use of a separate absorbance instrument, neither of these solutions is optimal. In this work, we propose a mathematical correction procedure based on the intensity of Raman scatter from water. This procedure was found to reduce the error after correction by up to 50% in comparison with two absorbance correction procedures. Furthermore, it does not require the use of a separate absorbance measurement, and it is applicable to on-line and in situ EEM recordings, where the IFE would otherwise cause problems.
  •  
43.
  • Limbut, W, et al. (author)
  • A reusable capacitive immunosensor for carcinoembryonic antigen (CEA) detection using thiourea modified gold electrode
  • 2006
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 561:1-2, s. 55-61
  • Journal article (peer-reviewed)abstract
    • A capacitive immunosensor based on a self-assembled monolayer (SAM) of thiourea on gold electrode has been developed. Anti-carcinoembryonic antigen (anti-CEA) was immobilized on a self-assembled thiourea monolayer (SATUM) via covalent coupling. Under optimum conditions, the decrease in capacitive signal when carcinoembryonic antigen (CEA) standard was injected could be determined with a detection limit of 10 pg ml(-1) and linearity in the range of 0.01-10 ng ml(-1). The immobilized anti-CEA on SATUM gold electrode was stable and after regeneration good reproducibility of the signal could be obtained tip to 45 times with an RSD lower than 3.4%. Good agreement was obtained when CEA concentrations of human serum samples determined by the flow injection capacitive immunosensor system were compared to those obtained using an enzyme linked fluorescent assay (ELFA) method (P < 0.05). (c) 2006 Elsevier B.V. All rights reserved.
  •  
44.
  • Liu, Yang, et al. (author)
  • Rapid high throughput assay for fluorimetric detection of doxorubicin - Application of nucleic acid-dye bioprobe
  • 2007
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 587:1, s. 47-51
  • Journal article (peer-reviewed)abstract
    • A double stranded DNA based fluorescence bioprobe for anticancer agent (doxorubicin) detection is described. This method provides a new way for sensitive DNA/drug interaction study by a homogeneous assay. The probe employs the long-wavelength intercalating fluorophore TOTO-3((R)) (TT3). The anticancer agent, doxorubicin, which interacts with the DNA-TT3 complex, was indirectly measured by the decrease in the fluorescence intensity. Various oligonucleotides with different sequences were examined. Doxorubicin has preference for the oligonucleotide 5'AGCACG3'. Enhanced fluorescence observed for the TT3 intercalation with this oligonucleotide makes the DNA-dye complex a suitable bioprobe for doxorubicin detection by competitive assay. A home-built CCD camera setup was applied along with 384 well plate assay format for high throughput fluorescence imaging. The detection limit can be as low as 25 ng mL(-1) with an upper limit of 100 mu g mL(-1). The recovery test with spiked serum sample shows that this method can be a potential routine method for therapeutic drug monitoring (TDM). (c) 2007 Elsevier B.V. All rights reserved.
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45.
  • Macken, Stephen, et al. (author)
  • Towards integrated devices for computer screen photo-assisted multi-parameter sensing
  • 2009
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 632:1, s. 143-147
  • Journal article (peer-reviewed)abstract
    • The computer screen photo-assisted technique (CSPT) utilizes consumer electronic devices such as computer screens and web cameras for distributed chemical sensing. Key to this method is the development of small and disposable sensing assays able to aid the CSPT optical detection, and the evaluation of multiple indicators. Here we demonstrate CSPT identification of fluorescent indicators from individual 100 mu m SU-8 (10) pillars covering an area of 4 mm x 4 mm with a density of 47 elements mm-2. The extraction of distinctive spectral fingerprints is aided by the exploitation of a three-band Moire interference that enables the partial Bayer decoding of the CSPT images.
  •  
46.
  • Malinovskiy, Dmitry, et al. (author)
  • Performance of diffusive gradients in thin films for measurements of the isotopic composition of soluble Zn
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 537:1-2, s. 401-405
  • Journal article (peer-reviewed)abstract
    • The application of diffusive gradients in thin films (DGT) samplers for measurements of the isotopic composition of soluble Zn by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) was tested under laboratory conditions. The effect of diffusion in hydrogels as a possible source of fractionation was investigated by measuring Zn isotope ratios for different fractions of Zn accumulated by DGT and comparing with the bulk isotope composition of the solution. An important finding of this study is that, provided quantitative elution is obtained, no fractionation of Zn isotopes due to the diffusion process is detectable within the reported precision of MC-ICPMS measurements. Consequently, DGT samplers are suitable for studies of the Zn isotopic composition in natural waters.
  •  
47.
  • Mandenius, Carl-Fredrik, 1954-, et al. (author)
  • Monitoring of influenza virus hemagglutinin in process samples using weak affinity ligands and surface plasmon resonance
  • 2008
  • In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 623, s. 66-75
  • Journal article (peer-reviewed)abstract
    • Surface plasmon resonance (SPR) was used to screen the interaction between a variety of affinity ligands and hemagglutinin (HA) from human influenza virus, with the aim of identifying low affinity ligands useful for the development of a rapid bioanalytical sensor. Three sialic acid-based structures and four lectins were evaluated as sensor ligands. The sialic acid-based ligands included a natural sialic acid-containing glycoprotein, human α1-acid glycoprotein (α1-AGP), and two synthetic 6′-sialyllactose-conjugates, with varying degree of substitution. The interaction of HA with the four lectin-based ligands, concanavalin A (Con A), wheat germ agglutinin (WGA), Maackia amurensis lectin (MAL), and Sambucus nigra agglutinin (SNA), showed a wide variation of affinity strengths. Affinity and kinetics data were estimated. Strong affinities were observed for Con A, WGA, α1-AGP, and a 6′-sialyllactose-conjugate with a high substitution degree, and low affinities were observed for MAL and a 6′-sialyllactose-conjugate with low substitution. The main objective, to identify a low affinity ligand which could be used for on-line monitoring and product quantification, was met by a 6′-sialyllactose–ovalbumin conjugate that had 0.6 mol ligand per mol carrier protein. The apparent affinity of this ligand was estimated to be 1.5 ± 0.03 μM (KD) on the SPR surface. Vaccine process samples containing HA were analyzed in the range 10–100 μg HA mL−1 and correlated with single-radial immunodiffusion. The coefficient of variation on the same chip was between 0.010 and 0.091.
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48.
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49.
  • Markowski, Piotr, et al. (author)
  • Simultaneous determination of l-arginine and 12 molecules participating in its metabolic cycle by gradient RP-HPLC method. Application to human urine samples
  • 2007
  • In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 605:2, s. 205-217
  • Journal article (peer-reviewed)abstract
    • We have developed and described a highly sensitive, accurate and precise reversed-phase high-performance liquid chromatography (RP-HPLC) method for the simultaneous determination of l-arginine and 12 molecules participating in its metabolic cycle in human urine samples. After pre-column derivatization with ortho-phthaldialdehyde (OPA) reagent containing 3-mercaptopropionic acid (3MPA), the fluorescent derivatives were separated by a gradient elution and detected by fluorescence measurement at 338 nm (excitation) and 455 nm (emission). l-Arginine (ARG) and its metabolites: l-glutamine (GLN), NG-hydroxy-l-arginine (NOHA), l-citrulline (CIT), NG-monomethyl-l-arginine (NMMA), l-homoarginine (HARG), asymmetric NG,NG-dimethyl-l-arginine (ADMA), symmetric NG,NG′-dimethyl-l-arginine (SDMA), l-ornithine (ORN), putrescine (PUT), agmatine (AGM), spermidine (SPERMD) and spermine (SPERM) were extracted in a cation-exchange solid-phase extraction (SPE) column and after derivatization separated in a Purospher® STAR RP-18e analytical column. The calibration curves of analysed compounds are linear within the range of concentration: 45-825, 0.2-15, 16-225, 12-285, 0.1-32, 15-235, 0.1-12, 0.1-12, 10-205, 0.02-12, 0.1-24, 0.01-10 and 0.01-8 nmol mL-1 for GLN, NOHA, CIT, ARG, NMMA, HARG, ADMA, SDMA, ORN, PUT, AGM, SPERMD and SPERM, respectively. The correlation coefficients are greater than 0.9980. Coefficients of variation are not higher than 6.0% for inter-day precision. The method has been determined or tested for limits of detection and quantification, linearity, precision, accuracy and recovery. All detection parameters of the method demonstrate that it is a reliable and efficient means of the comprehensive determination of ARG and its 12 main metabolites, making this approach suitable for routine clinical applications. The levels of analysed compounds in human urine can be successfully determined using this developed method with no matrix effect. © 2007 Elsevier B.V. All rights reserved.
  •  
50.
  • Melander, Claes, et al. (author)
  • Investigation of micro-immobilised enzyme reactors containing endoglucanases for efficient hydrolysis of cellodextrins and cellulose derivatives
  • 2005
  • In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 550:1-2, s. 182-190
  • Journal article (peer-reviewed)abstract
    • Cellulases hydrolysing the interior parts of cellulose, also called endoglucanases, were immobilised in micro-immobilised enzyme reactors (RIMER) made of porous silicon with the purpose of investigating the use of such mu IMERs for hydrolysis of cellodextrins and soluble cellulose derivatives. The endoglucanases Trichoderma reesei Cel 12A (TrCel 12A) and Bacillus agaradhaerens Cel 5A (BaCel 5A) were covalently coupled to the surface of a silicon microchip through Schiff base formation. For characterisation cellohexaose was used as substrate for the immobilised enzymes. The characteristics of the RIMER were investigated by studying the product formation when varying the concentration, flow-rate, temperature and pH of the substrate solution. Hydrolysis was performed in the RIMER connected on-line to a chromatographic system, where the products were separated and detected using high-performance anion exchange chromatography (HPAEC) coupled to pulsed amperometric detection (PAD). A comparison of the hydrolytic pattern between BaCel 5A and TrCel 12A was carried out and the results show that the two investigated endoglucanases give specific hydrolytic patterns in the products formed that provide important information about the enzymes. The RIMERs are robust and can be employed continuously over a period of at least several days. Moreover, on appropriate storage, no activity loss is seen after 60 days. The ability of the BaCel 5A containing RIMER to perform hydrolysis of derivatised cellulose was also investigated using carboxymethyl cellulose (CMC) as substrate. Separation and detection were carried out using size exclusion chromatography (SEC) with refractive index detection (RI). The results show that the RIMERs are robust and can be employed for on-line hydrolysis of both cellodextrins and derivatised cellulose of high molecular weight. (c) 2005 Elsevier B.V. All rights reserved.
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