Biomedical subjects

G Wünsch

Publications and source records attributed to G Wünsch.

9 recordsLinked to original sources

PubMed2003

Human biomonitoring of pyrethrum and pyrethroid insecticides used indoors: determination of the metabolites E-cis/trans-chrysanthemumdicarboxylic acid in human urine by gas chromatography-mass spectrometry with negative chemical ionization.

This work describes a gas chromatographic-mass spectrometric method employing negative chemical ionization (NCI) for the determination of E-cis/trans-chrysanthemumdicarboxylic acid (CDCA) in human urine used as a biomarker for the exposure to pyrethrum and/or certain pyrethroids in insecticide formulations applied indoors. Mixed-mode solid phase extraction was utilized for sample cleanup. Extraction recoveries ranged from 92 to 104% (2-9% R.S.D.). The acids were esterified with 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) allowing both their gas chromatographic separation and their sensitive mass spectrometric detection under NCI conditions. Detection limits of ca. 0.05 microg/l urine were achieved.

Calibration↗

PubMed2003

Development of a gas chromatography-mass spectrometry method for the determination of household insecticides in indoor air.

This work presents a GC-MS method for the determination of 17 household insecticides and acaricides in indoor air. Air samples were collected with a sampling train which consisted of a glass fibre filter and two polyurethane foam plugs, followed by a high-volume air pump. Filters and plugs were analysed separately. The overall recoveries ranged from 85 to 109% (4-11% RSD). Minimum method detection limits between 0.1 and 5 ng/m3 were determined.

Air Pollution, Indoor↗

PubMed2002

Verapamil drug metabolism studies by automated in-tube solid phase microextraction.

Verapamil is a common calcium antagonist described with antianginal, antihypertensive and antiarrythmic properties. The metabolites of verapamil have also shown pharmacological properties and therefore sample preparation and analysis techniques capable of metabolic screening for verapamil are important. In-tube SPME is a relatively new method integrating sample extraction, concentration and introduction into one single step without the use of organic solvents. The capability of in-tube SPME in bioanalysis has been reviewed but there has been no application described in the field of drug metabolism. Since automation and interfacing of in-tube SPME coupled to liquid chromatography-mass spectrometry (LC-MS) is possible, we confirm in this study that it is a powerful method to monitor the main metabolites of verapamil in various biological matrices like plasma, urine and cell culture media. Further, we show that it could also be used in routine pharmacokinetics measurements. An in-tube SPME LC-MS method was developed to extract and analyze the metabolic profile of verapamil from biological matrices. The detection limit for verapamil, gallopamil, norverapamil and PR22 were 52, 53, 65 and 83 ng/ml (UV detection) and 5, 6, 6 and 8 ng/ml (MS detection), respectively. The precision of the method was calculated in various biological matrices and the average % R.S.D. (N=5) for verapamil, gallopamil, norverapamil and PR22 was 3.9, 3.7, 3.8 and 4.3% (MS detection), respectively. The linear dynamic range was determined to be 100-800 ng/ml (UV detection) with a total sample preparation and analysis time of 34 min.

Animals↗

PubMed2001

Multi-element sewer slime impact pattern--a quantitative characteristic enabling identification of the source of heavy metal discharges into sewer systems.

The capability of sewer slime to accumulate heavy metals from municipal wastewater can be exploited to identify the sources of sewage sludge pollution. Former investigations of sewer slime looked for a few elements only and could, therefore, not account for deviations of the enrichment efficiency of the slime or for irregularities from sampling. Results of ICP-MS multi element determinations were analyzed by multivariate statistical methods. A new dimensionless characteristic "sewer slime impact" is proposed, which is zero for unloaded samples. Patterns expressed in this data format specifically extract the information required to identify the type of pollution and polluter quicker and with less effort and cost than hitherto.

Algorithms↗

PubMed1998

Automated simultaneous quantification of the immunosuppressants 40-O-(2-hydroxyethyl) rapamycin and cyclosporine in blood with electrospray-mass spectrometric detection.

A new analytical method to quantify 40-O-(2-hydroxyethyl)rapamycin (SDZ RAD) and cyclosporine (Cs) simultaneously in blood is presented. The combination of an on-line solid-phase extraction step with an HPLC system coupled to an electrospray mass spectrometer gave excellent specificity, sensitivity, and reproducibility. Aliquots of deproteinized blood samples were injected into the HPLC system and extracted on-line, using a conventional C18 guard column. The extract was eluted from the guard column in the backflush mode and injected into the liquid chromatography-mass spectrometry system. The calibration functions for SDZ RAD and Cs extracted from blood with added analyte were linear from 0.15 to 30 microg/L (r2 = 0.999) and from 1.5 to 1000 microg/L (r2 = 0.999), respectively. The CVs of peak areas were 6.2% at 10 microg/L SDZ RAD (n = 6) and 6.2% at 100 microg/L Cs (n = 6). Recovery ranged from 84.3% to 102.3% for SDZ RAD and from 81.7% to 92.2% for Cs. The lower limit of detection for both drugs was 0.05 microg/L. A rate of four samples per hour was maintained during the consecutive analysis of SDZ RAD and Cs in >500 blood samples with one single extraction and analytical column. The method described is a powerful tool for the simultaneous determination of SDZ RAD and Cs in blood. It works without time-consuming sample preparation steps and with excellent reproducibility. Because of the detection performance of electrospray mass spectrometry, this system offers flexibility in the working range, which is essential for therapeutic drug monitoring under different conditions.

Chromatography, High Pressure Liquid↗

PubMed1997

Application of on-line HPLC-1H NMR to environmental samples: analysis of groundwater near former ammunition plants.

Coupling of HPLC to NMR was applied for the first time to the analysis of environmental samples, i.e., water samples from an ammunition hazardous waste site. Using the continuous flow mode at very low flow rates (< or = 0.017 mL/min) and large volume injection (400 microL), the confirmation of many nitroaromatic compounds could be achieved down to the microgram-per-liter level after solid phase extraction of a groundwater sample from a former ammunition production site. At a flow rate of 0.006 mL/min, it is possible to detect less than 29 nmol (5 micrograms) of 1,3-dinitrobenzene injected on a 75 mm x 4 mm reversed phase C-18 column (particle size, 5 microns). The results obtained by HPLC-NMR are compared to those obtained by HPLC-PDA (photodiode array) of the same sample, demonstrating that many more compounds can be identified by the former compared to the latter method as a result of coelution of major and minor components in the HPLC chromatogram.

Chromatography, High Pressure Liquid↗

PubMed1996

Platinum solubility of a substance designed as a model for emissions of automobile catalytic converters.

Automobile catalytic converters emit nanocrystalline platinum attached to alumina particles. For investigations about the bioavailability of Pt from these particles a model substance with approx. 5% Pt on alumina has been prepared and characterized by physical methods (ESCA, XRD, TEM, DTA, TG). Measuring the platinum solubility of these samples in different solvents revealed high amounts that can be explained assuming a corrosion process. The portion of soluble platinum is dependent on the particle size distribution. For a comparative study platinum black has been used. In general the platinum determination has been carried out by electrothermal atomic absorption spectrometry (ET-AAS). The comparison of ET-AAS results with determinations by adsorptive voltammetry (formazone method) allowed to distinguish between elemental and ionic platinum; in solution samples only ionic platinum has been present. UV spectra of extracts have been used for the semi-quantitative platinum speciation in solutions.

Journal Article↗

PubMed1996

Isotope dilution - high efficiency nebulization-ICP-MS: The coupling of accuracy and sensitivity.

If sample pretreatment, nebulization and method of calibration are suitably adapted to each other the performance of inductively coupled plasma - mass spectrometry ICP-MS can be greatly increased. High accuracy is obtained by high precision and low bias. For a given concentration higher sensitivity means higher count rates and therefore higher precision. Systematic errors are minimized by employing a definitive method of calibration. Increased sensitivity is obtained by introducing higher amounts of sample into the measurement system via high efficiency nebulizers (ultrasonic nebulizer, hydraulic-high pressure nebulizer according to Berndt and concentric high efficiency nebulizer according to Meinhard). Because this means also higher matrix effects a combination of ion chromatographic (IC-TMS) and thermal trace-matrix-separation by aerosol desolvation (T-TMS) is introduced. Isotope dilution (ID) proves to be the calibration most suitable to achieve the highest accuracy. First applications on the analysis of refractory metals (e.g. Ti, V, Nb, Ta) and non-metals (e.g. P, S, As, Se) showed recoveries of 60-105%, an imprecision of the recoveries of 2-50%, but an overall inaccuracy of only 0.1 to 4%.

Journal Article↗

PubMedDate not supplied

Kinetics and stoichiometry in the Karl Fischer solution.

The mechanisms of the Karl Fischer (K.F.) reaction are reviewed and further investigated. Both kinetic measurements of the iodine concentration and chromatographic determinations of the reaction products were performed. In alcoholic solutions mainly alkyl sulfite is oxidized, and a reaction via partial formation of sulfur trioxide is proposed. In methanol an exact 1:1 stoichiometry (H2O:I2) has been verified. In the aprotic, dipolar solvents acetonitrile, DMF and propylene carbonate HSO3- is oxidized by iodine. Based on formation and subsequent hydrolysis of base - SO3 adducts the stoichiometric factor for water is determined by type and concentration of the base, by the concentration of water and by the solvent itself. - In K.F. reagents the oxidation of SO2 by aerial oxygen to sulfate and alkyl sulfate takes place as a side reaction.

Journal Article↗