Biomedical subjects

B Køppen

Publications and source records attributed to B Køppen.

7 recordsLinked to original sources

PubMed1998

Determination of acidic herbicides using liquid chromatography with pneumatically assisted electrospray ionization mass spectrometric and tandem mass spectrometric detection.

Liquid chromatography-pneumatically assisted electrospray mass spectrometry with negative ionization has been used for the determination of acidic herbicides in ground water. Eighteen pesticides or pesticide degradation products belonging to several different groups of acidic herbicides (phenoxy acids, sulfonylureas, phenols, etc.) were covered in the study. Optimization of electrospray inlet conditions is described as well as results from investigations of the linearity of the detector response. Conditions for tandem mass spectrometry (MS-MS) detection of characteristic daughter ions formed by collision-induced dissociation (CID) of the parent ion are described and a comparison of obtainable instrument detection limits by single MS and MS-MS was made. Detection limits using MS in the selected ion monitoring (SIM) mode were generally in the order of 1 microgram/l or below, whereas detection limits were three-four times higher using MS-MS detection. A principle of analysis is proposed based on single quadrupole MS as a method for quantitative determination followed by verification of positive findings by CID MS-MS. Application of the method for detecting acidic herbicides residues in a "real-world" ground water sample is demonstrated.

Calibration↗

PubMed1998

Occurrence of pesticides in Danish shallow ground water.

Shallow ground water from four different catchment areas, two sandy and two clayey locations, were investigated for content of pesticides and -degradation products. The samples were taken from screens in extraction wells placed from 1.5 to 5 meters below surface 46 different compounds were included in the study, and the analysis were performed with liquid chromatography mass spectrometry (LC-MS) with detection limits below 0.01 microgram/L. In total more than 300 samples were analysed and the most frequently found compounds being atrazine and its degradation products, bentazone, MCPA, metamitron, isoproturon and simazine. 23 out of the 46 compounds were detected in one or more samples. Four different sulfonylurea herbicides were included in the study as they to some extent have substituted phenoxyacid herbicides in agricultural practice and in much lower dosage. Sulfonylurea herbicides did not occur in any samples.

Agriculture↗

PubMed1996

Determination of polar pesticides in ground water using liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization.

A method is described for determination of pesticides in ground water by liquid chromatography combined with mass spectrometry (LC-MS) using atmospheric pressure chemical ionization (APCI). The study demonstrates the sensitivity of the technique, with detection limits for water samples of about 0.001-0.005 microgram/l, corresponding to 50-300 pg injected. Performance data for the method such as recovery, precision and linearity are also reported. It is illustrated that the technique is applicable for many different types of pesticide structures, such as triazines, phenylurea herbicides, acetanilides, organophosphorus insecticides, etc. Twelve different pesticides and pesticide degradation products are included in the study. The optimization of inlet conditions with respect to sheath gas pressure, vaporizer temperature, capillary temperature and corona current is reported. Applicability of the method for analysis of "real-world" ground water samples is demonstrated.

Chromatography, High Pressure Liquid↗

PubMed1988

Automatic headspace gas chromatographic method for the simultaneous determination of trichloroethylene and metabolites in blood and urine.

Trichloroethylene, trichloroethanol and trichloroacetic acid (TCA) were quantitated in blood and urine by automated headspace gas chromatography using a fused-silica capillary column coated with 3-micron silicone SE-30 and an electron-capture detector. Total trichloroethanol was determined after enzymatic hydrolysis with beta-glucuronidase and analysed together with trichloroethylene and TCA as chloroform, which are produced by decarboxylation. Analytical conditions were developed under which the thermal decomposition of TCA was optimal. The automated headspace gas chromatography is rapid and good precision is possible. Sample preparation is simple and the sensitivity of the procedure (0.02 microgram/ml) makes it suitable to estimate occupational exposure to trichloroethylene and other halocarbons in humans.

Autoanalysis↗

PubMed1988

Determination of trichloroethylene metabolites in rat liver homogenate using headspace gas chromatography.

An headspace gas chromatographic (HSGC) method for determination of trichloroethylene metabolites in rat liver homogenates is described. These metabolites are chloral hydrate (CH), trichloroethanol (TCE), trichloroacetic acid (TCA) and the glucuronic acid conjugate of trichloroethanol (TCE-beta-glucuronide). The method is based on selective thermal conversion of CH and TCA into chloroform, which is determined together with trichloroethanol by HSGC using electron-capture detection. TCE-beta-glucuronide was determined as the difference between free TCE and total TCE after enzymatic hydrolysis with beta-glucuronidase. Synthesized TCE-beta-glucuronide was used to compare the efficiency of enzymatic and acid hydrolysis of the conjugate. Enzymatic hydrolysis was found to be advantageous for determination of TCE-beta-glucuronide.

Animals↗

PubMed1985

Headspace gas chromatographic determination of beta-galactosidase activity using electron-capture detection.

A headspace gas chromatographic method for the determination of beta-galactosidase (E.C. 3.2.1.23) activity is described. The method, in which 2,2,2-trichloroethyl beta-D-galactopyranoside (beta-TCG) is used as substrate, involves determination of the liberated 2,2,2-trichloroethanol by gas chromatography with electron capture detection. The preparation of beta-TCG and of 2,2,2-trichloroethyl alpha-D-galactopyranoside is described. A Km = 0.80 mM was found for the enzymatic hydrolysis of beta-TCG employing beta-galactosidase from Escherichia coli. The assay has been applied to the quantitative determination of E. coli bacteria.

Chromatography, Gas↗

PubMed1984

Assay for beta-glucuronidase utilizing headspace gas chromatography.

An assay for beta-glucuronidase is described. The assay uses 1-(beta-D-glucopyranuronosyl)pyridinium hydroxide, inner salt, as substrate and the quantitative determination is performed with headspace gas chromatography, measuring one of the products, pyridine, in the gas phase. The assay has been developed utilizing commercially available beta-glucuronidase (EC 3.2.1.31.) from Escherichia coli, and has been applied to various sources of beta-glucuronidase. Crude homogenates can be assayed directly with a minimum of manipulative steps and the method is suited for automation.

Animals↗