| 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. |
- 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
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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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| 3. |
- 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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| 4. |
- 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
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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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
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| 10. |
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| 11. |
- 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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| 12. |
- 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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| 13. |
- 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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| 14. |
- 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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| 15. |
- 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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| 16. |
- 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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| 17. |
- Malinovskiy, Dmitry, et al.
(författare)
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Simplified method for the Re-Os dating of molybdenite using acid digestion and isotope dilution ICP-MS
- 2002
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 463:1, s. 111-124
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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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| 18. |
- 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
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 487:1, s. 43-50
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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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| 19. |
- Piletska, Elena V., et al.
(författare)
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Biotin-specific synthetic receptors prepared using molecular imprinting
- 2004
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Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 504:1, s. 179-183
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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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| 20. |
- Piletsky, Sergey, et al.
(författare)
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Custom synthesis of molecular imprinted polymers for biotechnological application - Preparation of a polymer selective for tylosin
- 2004
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Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 504:1, s. 123-130
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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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| 21. |
- Winquist, Fredrik, et al.
(författare)
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A hybrid electronic tongue
- 2000
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 406:2, s. 147-157
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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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| 22. |
- Winquist, Fredrik, et al.
(författare)
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Flow injection analysis applied to a voltammetric electronic tongue
- 2002
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 471:2, s. 159-172
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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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| 23. |
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| 24. |
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| 25. |
- Beni, Valerio, et al.
(författare)
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Voltammetric behaviour at gold electrodes immersed in the BCR sequential extraction scheme media : Application of underpotential deposition–stripping voltammetry to determination of copper in soil extracts
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 502:2, s. 195-206
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Tidskriftsartikel (refereegranskat)abstract
- The development of mercury-free electroanalytical systems for in-field analysis of pollutants requires a foundation on the electrochemicalbehaviour of the chosen electrode material in the target sample matrices. In this work, the behaviour of gold working electrodes in the mediaemployed in the BCR sequential extraction protocol, for the fractionation of metals in solid environmental matrices, is reported. All three ofthe BCR sequential extraction media are redox active, on the basis of acidity and oxygen content as well as the inherent reducing or oxidisingnature of some of the reagents employed: 0.11M acetic acid, 0.1M hydroxylammonium chloride (adjusted to pH 2) and 1M ammoniumacetate (adjusted to pH 2) with added trace hydrogen peroxide. The available potential ranges together with the demonstrated detection oftarget metals in these media are presented. Stripping voltammetry of copper or lead in the BCR extract media solutions reveal a multi-peakbehaviour due to the stripping of both bulk metal and underpotential metal deposits. A procedure based on underpotential deposition–strippingvoltammetry (UPD-SV) was evaluated for application to determination of copper in 0.11M acetic acid soil extracts. A preliminary screeningstep in which different deposition times are applied to the sample enables a deposition time commensurate with UPD-SV to be selected sothat no bulk deposition or stripping occurs thus simplifying the shape and features of the resulting voltammograms. Choice of the suitabledeposition time is then followed by standards addition calibration. The method was validated by the analysis of a number of BCR 0.11Macetic acid soil extracts. Good agreement was obtained been the UPD-SV method and atomic spectroscopic results.
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| 26. |
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| 27. |
- Engström, Emma, et al.
(författare)
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Multi-elemental characterization of soft biological tissues by inductively coupled plasma-sector field mass spectrometry
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 521:2, s. 123-135
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Tidskriftsartikel (refereegranskat)abstract
- The performance of double-focusing, sector field ICP-MS (ICP-SFMS) for the multi-elmental analysis of soft tissues following microwave-assisted digestion with nitric acid was eveluated and factors affecting method limits of detection discussed. Accuracy was assessed by replicate analyses of certified reference materials and by participation in performance evaluation programs; the precision was better than 5% relative standard deviation (RSD) for the majority of elements. Cl was the only element for which ICP-SFMS data consistently deviated from certified concentrations in the reference materials tested. Comparison between results obtained by ICP-SFMS and ICP optical emission spectrometry showed good agreement for elements present in tissues at concentrations above 2 μg g-1. The concentrations of 68 elements in different fish and animal soft tissues (muscle, liver, kidney, lung and brain) are presented, and, where possible, compared to previously published data.
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| 28. |
- Filippini, Daniel, et al.
(författare)
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Spectroscopic information retained in screen photo-assisted techniques
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 521:2, s. 237-244
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Tidskriftsartikel (refereegranskat)abstract
- The computer screen photo-assisted technique (CSPT), a recently reported method for characterization of colorimetric assays, has been modeled and the ability of the technique to retain key spectral features has been determined. The robustness of CSPT to operate with different kind of screens is demonstrated and a physical explanation of the result is provided. Simulated CSPT transmittances corroborate experimental results, and enable comparison with standard methods for qualitative and quantitative evaluation. © 2004 Elsevier B.V. All rights reserved.
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| 29. |
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| 30. |
- Gaspar, Szilveszter, et al.
(författare)
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Amperometric biosensor-based flow-through microdetector for microdialysis applications
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 525:1, s. 75-82
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Tidskriftsartikel (refereegranskat)abstract
- A new flow-through electrochemical microcell was fabricated, in order to be used as an on-line detector in microdialysis-based investigations. The microcell is obtained by sandwich-like assembling the electrode system patterned on a glass chip and a silicon rubber gasket bearing the fluidic elements (inlet, outlet, flow channel, and containers for reference and counter electrode). Four Pt microelectrodes (100 mum x 100 mum squares), a Pt counter electrode, and a Ag reference electrode were patterned on a 9 mm x 14 mm glass chip by thin film technology. The silicon rubber cover was fabricated using a polydimethylsiloxane based precursor and a plastic mold, and it avoids significant dilution of the sample before getting in contact with the sensing electrodes. The microdetector can be directly connected to the outlet of the microdialysis probe reducing significantly the delay between sampling and detection. The microelectrodes were modified with enzyme-based chemistries in order to detect glucose, glutamate, and choline by electrooxidation of the hydrogen peroxide produced in the reaction of the analytes with their corresponding oxidases. Problems concerning appropriate linear range, interference elimination, and cross-talk elimination were addressed. (C) 2004 Elsevier B.V. All rights reserved.
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| 31. |
- Herzog, Gregoire, et al.
(författare)
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Effect of humic acid on the underpotential deposition-strippingvoltammetry of copper in acetic acid soil extract solutions atmercaptoacetic acid-modified gold electrodes
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 511:1, s. 137-143
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical measurements were undertaken for the investigation of the underpotential deposition-stripping process of copper at bareand modified gold electrodes in 0.11M acetic acid, the first fraction of the European Union’s Bureau Communautaire de Références (BCR)sequential extraction procedure for fractionating metals within soils and sediments. Gold electrodes modified with mercaptoacetic acid showedhigher sensitivity for the detection of copper than bare gold electrodes, both in the absence and in the presence of humic acid in acetic acidsolutions, using the underpotential deposition-stripping voltammetry (UPD-SV) method. In the presence of 50 mg l−1 of humic acid, themercaptoacetic acid modified electrode proved to be 1.5 times more sensitive than the bare gold electrode. The mercaptoacetic acid monolayerformed on the gold surface provided efficient protection against the adsorption of humic acid onto the gold electrode surface. Variation of thehumic acid concentration in the solution showed little effect on the copper stripping signal at the modified electrode. UPD-SV at the modifiedelectrode was applied to the analysis of soil extract samples. Linear correlation of the electrochemical results with atomic spectroscopic resultsyielded the straight-line equation y (g l−1) = 1.10x − 44 (ppb) (R = 0.992, n = 6), indicating good agreement between the two methods.
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| 32. |
- Holmin, Susanne, et al.
(författare)
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Multivariate optimisation of electrochemically pre-treated electrodes used in a voltammetric electronic tongue
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 519:1, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- The use of experimental design as a tool to optimise electrochemically cleaned electrodes applied in a voltammetric electronic tongue is described. A simple and quick activation of electrode surfaces is essential for this type of device, especially for on-line applications in industrial processes. The electronic tongue consisted of four metal electrodes, e.g. Au, Ir, Pt, and Rh in a three-electrode configuration. Current was measured as a function of large potential pulses of decreasing amplitude applied to each electrode. Preliminary results showed that electrochemical cleaning activated the electrode surfaces to similar extent as polishing. Settings of potential and time for each electrode was determined with experimental design in a solution containing 1.0 mM K 4[Fe(CN)6] in 0.1 M phosphate buffer (pH 6.8). Electrode surfaces were deactivated in-between measurements in a complex liquid, like tea. Optimal settings for potential and time in the electrochemical cleaning procedure at each electrode were chosen at recoveries of 100% (compared to polished electrodes). The recoveries were larger than 100% when too large potentials and times were applied. This could be explained by the fact that the electrode areas increased and therefore also the current responses. Principal component analysis (PCA) was used to investigate the stability of the electrode settings at 100% recoveries. No obvious trends of drift in the signals were found. © 2004 Elsevier B.V. All rights reserved.
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| 33. |
- Khampha, Wanida, et al.
(författare)
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Specific detection of L-glutamate in food using flow-injection analysis and enzymatic recycling of substrate
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 518:1-2, s. 127-135
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Tidskriftsartikel (refereegranskat)abstract
- A flow injection analysis (FIA) system for specific determination of L-glutamate in food samples based on a bi-enzymatic amplification system has been developed. The content of L-glutamate in the sample was amplified by cycling between L-glutamate dehydrogenase (GIDH) and a novel enzyme, D-phenylglycine aminotransferase (D-PhgAT). In this system, GIDH converts L-glutamate to 2-oxoglutarate with concomitant reduction of NAD(+) to NADH. D-PhgAT transfers an amino group from D-4-hydroxyphenylglycine to 2-oxoglutarate, thus recycling L-glutamate. Accumulation of NADH in the course of the enzymatic recycling was monitored both by fluorescence and UV absorbance and used for quantification of L-glutamate. The assay was characterized by high long-term stability (at least 70 days) and good reproducibility (within-day and between-day RSDs were 4.3-7.3% and 8.9%). The fluorimetric assay was slightly more sensitive with a L-glutamate detection limit of 0.4 muM and linear range of 2.5-50 muM. The assay was specific for L-glutamate, with recoveries between 95-103% in the presence of 17 different amino acids tested one by one. The method was applied to analysis of real food samples and results were correlated with a commercial Boehringer Mannheim assay kit. (C) 2004 Elsevier B.V. All rights reserved.
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| 34. |
- Marand, Åsa, et al.
(författare)
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Extractable organic compounds in polyurethane foam with special reference to aromatic amines and derivatives thereof
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 510:1, s. 109-119
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Tidskriftsartikel (refereegranskat)abstract
- Methods for determination of aromatic amines and related compounds in flexible toluene diisocyanate (TDI)-based polyurethane (PUR) foam were investigated. The foam was extracted using 0.1% (w/v) aqueous acetic acid (HAc). Extraction solutions were analysed and aromatic amines were determined as ethyl chloroformate (Et) and pentafluoropropionic acid anhydride (PFPA) derivatives. The determinations were performed using liquid chromatography (LC) and mass spectrometry (MS) detection with electrospray ionisation (ESI) or gas chromatography (GC)-MS with chemical ionisation monitoring negative ions (NCI). The Et derivatives were determined using LC-ESI+-MS with detection limit of 2 pg of toluenediamine (TDA). The PFPA derivatives were determined using LC-ESI--MS or GC-NCI-MS with detection limits of 0.1 and 0.02 pg of TDA, respectively. Using trideuterium labelled TDA as internal standard, linear calibration curves were obtained in the range of 0.01-0.50 mug ml(-1) (n = 7), with correlation coefficients >0.999. When plotting calibration curves for TDA-PFPA derivatives determined using LC-MS against TDA-PFPA using GC-MS and TDA-Et using LC-MS, linear curves were obtained. The relative standard deviation (R.S.D.) for determination of TDA in foam extraction solutions were 13%. LC-MS determination of PFPA derivatives was more selective, as compared to LC-MS of Et derivatives.In foam extraction solutions, 2,4- and 2,6-TDA, several isomers of methylenedianiline (MDA) and dimers of TDA/TDI were observed. 2,4-TDA and 4,4'-MDA are possible human carcinogens. Hydrolysis of the extraction solution revealed a large pool of TDA/TDI compounds and oligomers. The concentration of TDA in foam was affected by the extraction media, temperature and duration. The choice of derivatisation procedure also affected the determination of TDA. In extraction solutions from six different commercially available flexible foam qualities 2,4- and 2,6-TDA were found in the range of 0-7 and 0-6 mug g(-1) foam, respectively. When flexible foam was heated, considerable higher concentrations of TDA were observed.
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| 35. |
- Richardson, Sara, et al.
(författare)
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Characterisation of the substituent distribution in starch and cellulose derivatives
- 2003
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 497:1-2, s. 27-65
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Forskningsöversikt (refereegranskat)abstract
- Derivatised polysaccharides are polymers from renewable sources of great importance in a whole range of different industries. However, only until recently have their characterisation been hampered by the lack of suitable instrumental methods or rather combination of suitable instrumentation. This review gives details on the state-of-the-art on polysaccharide analysis, especially focussing on starch and cellulose derivatives and the use of specific hydrolysing enzymes facilitating their analysis, reflecting recent work in the author’s respective laboratories.
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| 36. |
- Tang, AXJ, et al.
(författare)
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Immunosensor for okadaic acid using quartz crystal microbalance
- 2002
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Ingår i: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 471:1, s. 33-40
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Tidskriftsartikel (refereegranskat)abstract
- An immunosensor for the determination of okadaic acid (OA) using a quartz crystal microbalance (QCM) was developed and optimised in standard solutions. Several coupling techniques, protein A, protein G and polyethylenimine (PEI) with glutaraldehyde (GA) cross-linking, were investigated for the determination of okadaic acid and a very good result was obtained with PEI coupling. With the PEI coupling method, the optimisation of incubation time for the activation of PEI on the crystal surface using GA, the effect of the dilution factor of OA-bovine serum albumin (BSA) conjugate and the amount of antibody on crystal frequency were studied. Different molar ratios (4:1, 14:1, 30:1) of OA to bovine serum albumin for the conjugation were examined and the results using ELISA and a QCM showed that a ratio of 14:1 was slightly better than the other two. The strong attachment of the cross-linked complex to the gold surface resulted in an excellent storage lifetime of 38 days. However, the detection limit (1.9 mug/ml) and the sensitivity of the sensor were not satisfactory. Significant improvement of the performance of the device was obtained by incorporating an antibody-BSA hydrogel. Initial results showed that the minimum amount of analyte detectable and the sensitivity of the device were improved by 524- and 80-fold, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 37. |
- Tombelli, S, et al.
(författare)
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A DNA piezoelectric biosensor assay coupled with a polymerase chain reaction for bacterial toxicity determination in environmental samples
- 2000
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Ingår i: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 418:1
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report the realisation of a DNA piezoelectric biosensor coupled with the polymerase chain reaction (PCR) for the detection of a specific bacterial toxicity factor. Biotinylated 23-mer probes were immobilised on the streptavidin coated gold surface of a quartz crystal; streptavidin was covalently bound to the thiol/dextran modified gold surface. The hybridisation of the immobilised probe with a synthetic oligonucleotide was investigated; the absence of non-specific adsorption was verified using a non-complementary oligonucleotide. Many cycles of measurements can be performed on the same crystal surface by regenerating the single strand with 1 mM HCl. The same hybridisation reaction was then performed using real samples of DNA extracted from bacteria and amplified by PCR. The PCR product was a fragment of a specific gene of Aeromonas hydrophila. The piezoelectric biosensor was able to distinguish samples containing the gene or not; in this way it was possible to determine the pathogenicity of different Aeromonas strains isolated from water, vegetables or human specimens. Experiments with non-specific samples confirmed the absence of adsorption or non-specific effects on the quartz crystal treated with the reported procedure. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 38. |
- Wiberg, Kent, et al.
(författare)
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Parallel factor analysis of HPLC-DAD data for binary mixtures of lidocaine and prilocaine with different levels of separation
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 514:2, s. 203-209
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Tidskriftsartikel (refereegranskat)abstract
- A set of 17 samples containing a constant amount of lidocaine (667 muM) and a decreasing amount of prilocaine (667-0.3 muM) was analysed by LC-DAD at three different levels of separation, followed by parallel factor analysis (PARAFAC) of the data obtained. In Case 1 no column was connected, the chromatographic resolution (R-s) therefore being zero, while Cases 2 and 3 had partly separated peaks (R-s = 0.7 and 1.0). The results showed that in Case 1, analysed without any separation, the PARAFAC decomposition with a model consisting of two components gave a good estimate of the spectral and concentration profiles of the two compounds. In Cases 2 and 3, the use of PARAFAC models with two components resolved the underlying chromatographic, spectral and concentration profiles. The loadings related to the concentration profile of prilocaine were used for regression and prediction of the prilocaine content. The results showed that prediction of prilocaine content was possible with satisfactory prediction (RMSEP < 0.01). This study shows that PARAFAC is a powerful technique for resolving partly separated peaks into their pure chromatographic, spectral and concentration profiles, even with completely overlapping spectra and the absence or very low levels of separation.
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| 39. |
- Zagorodni, Andrei
(författare)
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Evaluation of results obtained by analysis of fractions
- 2004
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 512:2, s. 251-256
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Tidskriftsartikel (refereegranskat)abstract
- The paper discusses treatment of experimental data obtained from the monitoring of continuous processes by a series of batch analyses (i.e. by analysis of fractions sequentially collected during the process). Common errors that are committed when graphically representing and fitting such data are shown. An approach for identification of such errors in published data is presented. One error results from the incorrect positioning of the analysis results along the X-axis when plotting data. In the case of equal fractions, this results in a systematic error along the X-axis. For non-equal fractions, the error in the coefficients of the fitting equation can be both systematic and random. A correct representation does not introduce any error if the actual function is linear in the region of the fraction collection. This plotting method is also a satisfactory procedure for low curvature functions. Another error originates because of the incorrect application of the least squares method. The reason lies in the fact that the analysis of each fraction does not represent an instant value of the measured parameter, but rather the averaged value over some period of time or over some volume. The actual error depends on the curvature of the fitting function. Furthermore, a reader encounters difficulties when evaluating published scientific information because many authors do not explain the methods by which their data were plotted and fit. The presented approach to the evaluation of graphical data makes it possible to identify the described errors.
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