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Analytical and Bioanalytical Chemistry (v.363, #8)
First International Forum on Intelligent Analytical Solutions, September 24–26, 1998, Research Centre Jülich, Germany
by M. Rossbach (pp. 718-719).
On-line monitoring of traces of aromatic-, phenolic- and chlorinated components in flue gases of industrial scale incinerators and cigarette smoke by direct-inlet laser ionization-mass spectrometry (REMPI-TOFMS) by R. Zimmermann; H. J. Heger; A. Kettrup (pp. 720-730).
The combination of laser induced resonance-enhanced multiphoton ionization (REMPI) and time-of-flight mass spectrometry (TOFMS) represents a highly selective as well as sensitive analytical technique, well suited for species selective real-time, on-line monitoring of trace-gases. Results presented are obtained with a newly designed, mobile REMPI-TOFMS instrument, optimized for field applications. The mobile REMPI-TOFMS device either is equipped with a compact excimer laser (KrF, λ = 248 nm) or a small Nd:YAG laser (forth harmonic frequency, λ = 266 nm). A special effusive molecular beam inlet system was used, which allows direct inlet of flue gases from e.g. waste incinerators without memory effects for compounds of a molecular weight of up to 260–280 amu. Detection sensitivities in the sub-ppb region are achieved under field measurement conditions. Applications concerning on-line monitoring of combustion byproducts and fuel components are presented. This includes on-line analysis of polycyclic aromatic hydrocarbons (PAH) in the flue gas of a 0.5 MW waste incineration pilot plant, headspace analysis of wood gasification products and crude oil composition (fuel analysis) as well as highly time resolved (single puff resolution) on-line analysis of cigarette smoke. The application of the on-line REMPI-TOFMS monitor for continuous analysis of dioxin indicators in the flue gas of e.g. hazardous waste incinerators is discussed.
Immunochemical array for the identification of cross-reacting analytes by Michael Winklmair; Andreas J. Schuetz; M. G. Weller; Reinhard Niessner (pp. 731-737).
A method for the identification and quantification of cross-reacting analytes using competitive immunochemical assays is described. The method uses information both of antibodies with and without significant inhibition caused by a sample. Maximum concentrations of all possible analytes were estimated for all antibodies not showing a significant inhibition. These maximum concentrations could be used to exclude certain analytes from the further identification process. A minimum variance method was used for the identification of analytes from the data given by antibodies showing significant inhibition. All samples were measured in a parallel affinity sensor array (PASA). The PASA system allows the parallel performance of numerous individual immunochemical assays. Triazines were used as a model substance class. Samples containing either atrazine, terbuthylazine, simazine or deethylatrazine at different concentration levels were generated and analyzed in the PASA system. 11 out of 13 samples were correctly identified, 2 samples could not be identified without doubt, no wrong identification was observed. Samples of atrazine, terbuthylazine and simazine at a concentration level of 0.1 μg/L, the EU maximum admissible concentration for individual pesticides, and of deethylatrazine at 0.3 μg/L could be quantified.
Application of different polarimetric methods for the analysis of enzyme-catalyzed enantioselective reactions by H. Teves; T. Waniek; M. Pietzsch; C. Syldatk; M. Reuss (pp. 738-743).
Identification of model parameters in kinetic equations requires the determination of reactant concentrations in the course of time. In the case of enzyme catalyzed enantioselective reactions, three different polarimetric methods were used for concentration measurements obtained in both initial rate experiments and under dynamically changing conditions. Two on-line methods for the determination of different numbers of chiral species and a more universal off-line method were applied. For the investigated substrate 5-benzylhydantoin and the enzyme hydantoinase it is shown, that the obtained polarimetric data are most suitable for identification of kinetic parameters. Furthermore, it is demonstrated that on-line data of only one conversion allow for an assessment of an enzyme with regard to its enantioselectivity.
Industrial applications of SAW-sensors: on-line control of preparative HPLC by T. Wessa; S. Küppers; M. Rapp; J. Reibel; U. Stahl (pp. 744-748).
Results of on-line process control with an SAW-sensor based gas-sensor microsystem (SAGAS PC) are presented for industrial applications. The control of the solvent mixer of an HPLC-system was chosen as a typical example. All applications dealt with the detection and subsequent qualification as well as quantification of volatile organic compounds (VOC’s), e.g. organic solvents or even water by investigating their vapor. Mass-sensitive transducers, especially surface acoustic wave (SAW)-devices, have become a feasible tool for VOC-analytics. The measurement principle is based on frequency changes which are directly correlated with mass changes on the sensor surface and thus provide a particularly suitable signal transduction. The data analysis of all applications is based on pattern recognition methods, and focused on artificial neural networks for quantitative determination of these solvents and solvent-mixtures. The results obtained clearly showed the suitability of such a sensor system for on-line process-control purposes.
Determination of selenium at sub-μg/g-levels in biological materials by MIP-MS by M. Chiba; A. Shinohara (pp. 749-752).
Determination of Se in biological materials was attempted by microwave-induced plasma mass spectrometry (MIP-MS). (1) Serum samples were available after 10 times dilution with 0.5% nitric acid solution containing 0.1% Triton X-100. When oxygen gas was inserted into the plasma gas (nitrogen) in order to improve the combustion, the sensitivity was reduced to 45%. The detection limit of this method was 0.5 ng/mL. (2) Standard reference materials on commercial base were used to evaluate the accuracy of the Se determination by MIP-MS after microwave digestion. In samples like bovine liver and human hair with Se concentrations of more than 0.7 μg/g, the standard curve method after internal standard (IS) correction was acceptable. This procedure was unsuitable for samples with low Se concentrations such as milk powder (certified value of Se 0.11 μg/g), or plant leaf samples. (3) Instead of IS correction, the peak height of the spectrum was used for calculations from the matrix matched calibration curve. The results of all materials were close to the certified values, even at 25 ng/g. The detection limit of the MIP-MS with microwave digestion and IS correction was 0.05 ng/mL in standard solutions. The detection limit of the peak height method was 0.1 ng/mL and was estimated to be < 20 ng/g in plant materials.
Collimated scanning towards 3D-INAA of inhomogeneous large samples by H. W. Baas; M. Blaauw; P. Bode; J. J. M. De Goeij (pp. 753-759).
Kilogram-size samples can be analysed via Large Sample Instrumental Neutron Activation Analysis (LS-INAA), a method developed for samples which are inhomogeneous at the scale of a small sampling portion but which are assumed to be macroscopically homogeneous. However, extreme inhomogeneities affecting the total gamma-ray detection efficiency, may severely affect the quality of the analysis. A method has been developed to monitor large activated samples for the presence of such extreme inhomogeneities. In addition, a method has been developed for the determination of the spatial distribution of the induced radioactivity. These methods have been tested using a cylindrical phantom, simulating a large activated sample, with a local inhomogeneity. With a collimated detector, the activity was measured stepwise at 2 cm height intervals and 120° rotation intervals, resulting in 150 gamma-ray spectra at 45 seconds per spectrum. The activity distribution is retrieved from the measured spectra, employing a linear least squares matrix inversion of the detection efficiency matrix. This matrix is based on Monte Carlo computed detector responses and experimentally determined transmission coefficients. It is concluded that the proposed method can be employed in a system for 3D-INAA of large samples.
Determination of U and Th in soil and plants obtained from a high natural radiation area in China using ICP-MS and γ-counting by M. Yukawa; Y. Watanabe; Y. Nishimura; Y. Guo; Z. Yongru; H. Lu; W. Zhang; L. Wei; Z. Tao (pp. 760-766).
This study was carried out for the determination of 238U and 232Th concentrations in soil and various foods obtained in high natural radiation areas in China for estimating the internal radiation doses caused by these radionuclides. Knowledge of the daily dietary intakes of the nuclides through foods is essential to evaluate the internal radiation dose. Several analytical methods were evaluated for their applicability and quality assurance. The accuracy and precision of ICP-MS is considerably better for determining trace elements like U and Th in fine powder samples. The estimated annual effective dose is 0.302 μ Sv/y for 238U and 1.86 μ Sv/y for 232Th in the high natural radiation area, and 0.0101 μ Sv/y for 238U and 0.177 μ Sv/y for 232Th in the control area.
A new concept for the bioeffects-related analysis of xenoestrogens: Hyphenation of receptor assays with LC-MS by Martin Seifert; Gerald Brenner-Weiß; Stefanie Haindl; Michael Nusser; Ursula Obst; B. Hock (pp. 767-770).
The wide variety of known and unknown endocrine disruptors demands highly efficient methods for detecting the relevant endocrine disrupting pollutants. Bioeffects-related analysis is expected to solve this problem, combining biomolecular recognition processes with chemical analysis, which therefore reduces costs of instrumental chemical analysis to relevant samples. The hyphenation of both steps provides information on potential bioeffects, structure and concentration of the substances of interest. In this work the hyphenation of an enzyme-linked receptor assay (ELRA) with liquid chromatography-tandem mass spectrometry (LC-MSMS) for the analysis of estrogens and xenoestrogens is proposed. Both test systems have been validated with standards and spiked real water samples. The ELRA achieved a detection limit of 0.1 μg/L for 17β-estradiol (without preconcentration). With the LC-MSMS method, steroids could be detected down to 1 ng/L (with preconcentration). Two concepts for a tighter hyphenation of biomolecular interaction and chemical analysis are discussed: the on-line coupling of receptor-affinity chromatography (RAC) to LC-MSMS and the direct measurement of receptor-ligand complexes by LC-MSMS.
A modified method for the analysis of organics in industrial wastewater as directed by their toxicity to Vibrio fischeri by T. Reemtsma; Oliver Fiehn; Martin Jekel (pp. 771-776).
A method for the identification of toxic compounds in industrial wastewater is presented, consisting of sequential solid phase extraction (SPE), fractionation by HPLC and GC-MS for compound identification. All analytical steps are accompanied by an automated detection of the aquatic toxicity by luminescence inhibition of Vibrio fischeri, which helps to reduce the large number of samples and subsamples that have to be processed by exluding those without toxic effects. The advantages of this procedure in comparison to previous methods of toxicity directed water analysis are discussed. The procedure was successfully applied to various samples of tannery wastewater, showing that benzothiazoles account for the major toxicity of tanyard wastewater. For very polar wastewater constituents, such as in beamhouse wastewaters, the use of LC-MS/MS for the final compound identification is suggested.
A novel method for the determination of a PCB sum value by enzyme immunoassay to overcome the cross-reactivity problem by Andreas J. Schuetz; M. G. Weller; Reinhard Niessner (pp. 777-782).
Many attempts have been made to detect polychlorinated biphenyls (PCBs) by enzyme immunoassay (ELISA). All known ELISAs to PCBs show characteristic cross-reactivity problems. Without any prior information about the composition of the sample, no quantification of the total PCB content is possible. A chemical approach is shown to solve the cross-reactivity problem by the quantitative dechlorination of all PCB congeners to the single compound biphenyl. For the reductive dechlorination palladium on barium sulfate and ammonium formate were used. The dechlorination procedure was optimized to be performed at room temperature in methanol without the exclusion of oxygen or water. For the development of polyclonal biphenyl-antibodies the synthesis of the hapten biphenylhexanoic acid via Grignard cross-coupling is described and an immunization protocol is given. The purity of the used immunological reagents proved to be very crucial. The whole procedure was tested with spiked soil samples. The detection limit for PCBs (Clophen A50) in soil was 1 mg/kg (3.1 μmol/kg). This corresponds to a biphenyl concentration in methanol of 0.1 mg/L (0.6 μmol/L).
Application of ion chromatography for the investigation of the anionic and cationic composition in high-purity water production by V. D. Nguyen; H. Neumeister; G. Subklew (pp. 783-788).
A suitable and sensitive ion chromatographic measuring system for determining the main components at nanogram to milligram per liter levels in water samples from the electrodeionization process is presented. A modified Dionex system offers the possibility for the determination of anions and cations in the samples at ng/L, μg/L and mg/L levels. The ng/L level of anions and cations in 20–130 mL high-purity water can be analyzed immediately after preconcentration on appropriate exchange columns. The mg/L level samples are successfully determined by use of an auto-sampler. The quantification of each ion is achieved using the suppressor technique and a conductivity detector. Samples are taken from 5 steps of the electrodeionization process and stored in pre-cleaned FEP (fluorinated ethylene propylene) at 7 °C in darkness prior to the determination of chloride, nitrate, sulfate, carbonate, sodium, ammonium, potassium, calcium and magnesium. Eluents, ultrapure water and samples for the determination of carbonate were passed through special glass containers and flushed with helium gas to avoid the effect of atmospheric carbon dioxide. Results of the investigation of the cationic and anionic composition in water samples within the electrodeionization process are presented and discussed.