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Biomedical subjects

W Engewald

Publications and source records attributed to W Engewald.

13 recordsLinked to original sources
PubMed2003

One-step cleanup for PAH residue analysis in plant matrices using size-exclusion chromatography.

A new one-step cleanup procedure, based on size-exclusion chromatography (SEC), usable for the extracts from accelerated solvent extraction (ASE), Soxhlet extraction, or ultrasonic extraction (USE), is described. The method is suitable for the determination of polycyclic aromatic hydrocarbons (PAHs), especially from very complicated plant matrices (e.g. pine needles, deciduous leaves, mosses). The main improvement compared with previous conventional procedures is that analyte peaks barely overlap with matrix peaks in the chromatograms and that it is a very rapid and simple one-step procedure with clearly improved analytical performance. Essential advantages of this SEC procedure are the sharper GC-MS chromatograms for the PAH fraction at retention times between 9.2 and 12.0 min, distinctly separated substance peaks resulting in better analysis, shorter running times, and lower solvent consumption.

Acer↗
PubMed2003

Trace analysis of technical nonylphenol, bisphenol A and 17alpha-ethinylestradiol in wastewater using solid-phase microextraction and gas chromatography-mass spectrometry.

To enable high sample throughput, an automated solid-phase microextraction (SPME) method coupled with GC-MS for the trace analysis of technical nonylphenol, bisphenol A and 17alpha-ethinylestradiol was developed. The extraction performance of different SPME fibre coatings was examined, with polyacrylate proving most suitable. Although study of the extraction time showed that the analytes have not reached equilibrium after 3 h, as a compromise an extraction time of 1 h was applied in all the experiments with detection limits between 0.04 and 1 microg l(-1) for wastewater effluent. The mean reproducibility of the technique is 8% RSD. Carry-over effects are negligible. The linearity of calibration curves ranges over three orders of magnitude. The method was tested for determining the analytes in influents and effluents of constructed wetland plants and in model wastewater used in laboratory experiments.

Benzhydryl Compounds↗
PubMed2002

Adsorbent materials commonly used in air analysis for adsorptive enrichment and thermal desorption of volatile organic compounds.

A review is given dealing with commonly used adsorbent materials in ambient air analysis of volatile organic compounds (VOCs). The adsorbents covered in the paper are selected in consideration of their compatibility with thermal desorption. Initially, we discuss the requirements that an adsorbent should fulfill, and useful parameters for the selection and evaluation of an appropriate material. Then, the most important materials are presented considering their properties, advantages, and drawbacks. A few applications are given, but a complete review of sampling techniques and applications dealing with adsorptive enrichment and thermal desorption is beyond the scope of this paper.

Adsorption↗
PubMed2002

Determination of cannabinoids by gas chromatography-mass spectrometry and large-volume programmed-temperature vaporiser injection using 25 microl of biological fluid.

This paper presents a GC-MS confirmation method, based on large-volume programmed-temperature vaporisation (PTV) injection, for the determination of cannabinoids in plasma samples (or whole blood) with deuterium-labelled internal standards using only 25 microl of biological fluid. The analytes, Delta(9)-tetrahydrocannabinol (THC), 11-hydroxy-Delta(9)-tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-Delta 9-tetrahydrocannabinol (THC-COOH), were enriched by means of solid-phase extraction cartridges containing octadecyl-bonded silica and were, subsequently, methylated. A 20 microl aliquot of an extract in hexane was injected into a PTV in solvent split mode. Method development and the results of the analyses of standard reference material and real samples are presented and discussed. This micro-method is precise and sensitive enough to assess relevant cannabinoid levels in human blood for forensic investigations as well as for clinical applications.

Adolescent↗
PubMed2001

On the signal response of various pesticides in electrospray and atmospheric pressure chemical ionization depending on the flow-rate of eluent applied in liquid chromatography-tandem mass spectrometry.

The API-MS signal response of several pesticides (atrazine, simazine, isoproturon, diuron, chlorfenvinphos, chlorpyrifos, alachlor, trifluralin) depending on the flow-rate of eluent entering the MS interface was investigated. The investigations were based on API-MS-MS analyses of standard pesticide mixtures in the flow injection mode (FIA) at systematically varied eluent flow-rates using both an ESI interface (Turboionspray) and a heated nebulizer type APCI source. In the result, the individual compounds included in this study showed significant differences in their signal response behaviour depending on the flow-rate of eluent applied. The most hydrophobic compounds among the investigated pesticides (chlorpyrifos and trifluralin) showed drastic losses of sensitivity with increasing eluent flow-rate in both ESI and APCI, while more hydrophilic compounds like atrazine, simazine and isoproturon showed the expected signal response (concentration-sensitive in ESI, mass-flow-sensitive in APCI) at least within a certain range of flow-rates (200-600 microl/min in ESI, 200-2000 microl/min in APCI). These findings lead to the conclusion that application of a programmed HPLC eluent flow-rate may be advantageous to achieve maximum sensitivity of API-MS detection for all pesticides of interest. This is exemplified by the implementation of a flow gradient into an online SPE-HPLC-APCI-MS/MS method for improved analysis of pesticides in drinking water.

Atmospheric Pressure↗
PubMed2000

High extraction efficiency for POPs in real contaminated soil samples using accelerated solvent extraction

Systematic investigations were performed to study the dependence of the extraction efficiency of persistent organic pollutants (POPs), including chlorobenzenes, HCH isomers, DDX, PCB congeners, and PAHs, on the accelerated solvent extraction (ASE) operating variables solvent and temperature. Mixed soil samples from two locations with considerable differences in soil properties and contamination in the Leipzig-Halle region (Germany) were used. The objective was to optimize ASE for the extraction of POPs from real soil samples and to improve on the results achieved with Soxhlet extraction (SOX). Solvents with differing polarities were tested. Quadruple and triple determinations were performed on the two soils, respectively, between 20 and 180 degrees C in 20 degrees C steps. All the results were compared with those obtained by SOX, as well as, in some cases during preliminary studies, by ultrasonic extraction (USE). In ASE, the optimum conditions proved to be two extraction steps at 80 and 140 degrees C (average RSD 10.7%) with three static cycles (extraction time 35 min) using toluene as solvent and at a pressure of 15 MPa. Owing to the superior analyte/matrix separation by ASE, in many cases for real soil samples analytical values better by up to 1 order of magnitude or even more were obtained compared to SOX results.

Journal Article↗
PubMed2000

Application of spectral libraries for high-performance liquid chromatography-atmospheric pressure ionisation mass spectrometry to the analysis of pesticide and explosive residues in environmental samples.

The coupling of high-performance liquid chromatography (HPLC) and atmospheric pressure ionisation mass spectrometry (API-MS) seems to be the method of choice if good separation and selective detection of semi-volatile, thermolabile, and polar substances is required. Libraries of mass spectra will make the identification of unknown substances in complex environmental samples easier and more user-friendly. Unfortunately, existing GC-MS libraries are not applicable to HPLC-API-MS analysis. Thus, new and extensive mass spectral libraries were constructed. Several investigations of chromatographic (composition and salt concentration of the eluent) as well as mass spectrometric (orifice voltage) parameters and a few applications of real environmental samples are used to discuss the possibilities and limits of these libraries.

Atmospheric Pressure↗
PubMed1999

Programmed temperature vaporiser-based injection in capillary gas chromatography.

The application of programmed temperature vaporisation (PTV) in capillary gas chromatographic analysis is reviewed. The development of the different strategies as well as the state of the art are described. As the analytes are normally enriched in the PTV insert, the quoted papers are subdivided depending on whether the enrichment was carried out from organic solvents, from water or from gaseous media. Furthermore, the possibilities of PTVs for on-line coupling with sample preparation methods or other separation techniques and their use as thermoreactors are mentioned.

Chromatography, Gas↗
PubMed1991

[Carbon disulfide excretion in urine--a biological exposure test for the workplace and environmental concentration ranges].

The biological control procedure for carbon disulphide (CS2), the determination of free and bound CS2 in urine--a procedure already applied to hygienic surveillance--were modified by using gas chromatography and sulphide selective detection (FPD). The results obtained by the changed biological monitoring test in workplace and environmental surveillance are present and discussed. For CS2 concentrations at workplaces in the range of 8-54 mg/m3 a correlation coefficient of r = 0.56 (n = 11, p less than 0.07) was calculated for the mathematical connection of CS2 shift exposure and CS2 content in urine. For environmental exposures in the range of the CS2 immision short term threshold value (MIKK) of 0.03 mg/m3 the procedure may discriminate significantly exposure load from naturally occurring CS2 background.

Adult↗
PubMed1990

[Development and application of an environment dosimeter for carbon disulfide].

Construction, function, and quality of parameters of a newly developed passive dosimeter for carbon disulphide are described. CS2 adsorbed on chromosorb 101 is thermically desorbed and then dosed to a gas chromatograph via a gas sampling valve and finally determined by flame photometric detection (FPD). The dosimeter allows 24-hr immission and indoor measurements, respectively, and is also suitable as a personal dosimeter for the environmental concentration range. First practical measurement results are discussed.

Air Pollutants↗
PubMed1989

[Gas chromatography studies of exhaust air from an animal body waste salvage industry].

The proceedings of animal body waste salvage plants are-as you know-connected with intense smell importunities of the immediate environment. Suited desodorization plants are required to limit this problem of the environmental hygiene. The presupposition for a high effectiveness of these plants is to know the qualitative composition of the exhaust air, the analysis of which is the subject of the article in hand.

Abattoirs↗