| 11. |
- 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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| 12. |
- 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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| 13. |
- 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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| 14. |
- Larsson, Ted, et al.
(författare)
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Electron transfer between cellobiose dehydrogenase and graphite electrodes
- 1996
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 331:3, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- Electron transfer between the enzyme cellobiose dehydrogenase (CDH) and a flavin adenine dinucleotide (FAD) containing a catalytic active fragment of CDH (FAD-fragment) and a graphite electrode, respectively, was established. The current response in the presence of the enzyme substrate for graphite electrodes with CDH or the FAD-fragment adsorbed on the freshly polished graphite surface were compared with that of electrodes where CDH or the FAD-fragment were crosslinked in a redox polymer at the electrode surface. The initial slope, dj/d[S](S=0), where j is the current density and [S](S=0) the zero substrate concentration, was taken as a measure of the substrate response. For the electrodes with enzymes adsorbed directly on the surface, dj/d[S](S=0), was a factor of 3 lower than for electrodes prepared with the polymer mixture. The redox polymer based electrodes, with CDH and with FAD-fragment, both showed a high and close to equal substrate response. In contrast the surface adsorbed CDH gave a much higher substrate response than the FAD-fragment.
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| 15. |
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| 16. |
- Lutz, Mareike, 1967-, et al.
(författare)
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Effects of different additives on a tyrosinase based carbon paste electrode
- 1995
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Ingår i: Analytica Chimica Acta. - Amsterdam : Elsevier. - 0003-2670 .- 1873-4324. ; 305:1-3, s. 8-17
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Tidskriftsartikel (refereegranskat)abstract
- The influence of a number of solid and chemical additives on the sensitivity and operational stability of a tyrosinase carbon paste electrode was studied. Cyclic voltammograms were run of the electrochemically active catechol/o-quinone couple on unmodified and additive modified carbon paste electrodes without tyrosinase. This was done in order to study the influence of these additives on the pure electrochemistry of the carbon paste. The influence on the total system (additive and enzyme modified carbon paste electrode) was studied in the flow injection mode. In some instances a dramatic improvement of the direct electron transfer of the catechol/o-quinone couple was obtained with both solid and chemical additives included in the carbon paste. A similar improvement of biosensor sensitivity in the flow injection mode was obtained with most chemical additives whereas the solid additives had a negative impact on biosensor sensitivity. The results obtained in this work indicate that these additives influence the purely electrochemical processes at the carbon paste and/or the performance of the enzyme in the carbon paste environment. How and why these additives can possibly influence the biosensor performance are discussed. © 1995.
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| 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. |
- Palleschi, G., et al.
(författare)
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Amperometric tetrathiafulvalene-mediated lactate electrode using lactate oxidase absorbed on carbon foil
- 1990
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 234:2, s. 459-463
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The features of a new sensor for determining l-lactate are reported. The enzyme lactate oxidase and the mediator, tetrathiafulvalene (TTF), are absorbed on carbon foil disks previously bonded onto the ends of glass tubes. Linear calibration graphs were obtained in the range 10−4−10−3 M with physiological phosphate buffer (pH 7.35) and at 30°C with a response time of a few seconds. Calibration graphs in the range 10−3−10−2 M were also obtained and the difference in response times between these two ranges were investigated. The results are promising for assembling disposable lactate sensors for in vitro or for in or ex vivo measurements.
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| 20. |
- 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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