Biomedical subjects

J Freudenthal

Publications and source records attributed to J Freudenthal.

12 recordsLinked to original sources

PubMed1986

Quantitative determination of diethylstilboestrol in bovine urine with isotope dilution mass spectrometry.

A method has been described for the quantification of diethylstilboestrol (DES) in bovine urine. The determining step is based on isotope dilution mass spectrometry (IDMS). The chemical work-up consisted of enzymatic deconjugation, Sep-Pak clean-up and high-performance liquid chromatography (HPLC). The labelled compound synthesized for IDMS is hexadeutero DES (DES-2H6). The labelled compound is not only used to quantify DES, but also to check the recovery of the chemical work-up procedure, in order to avoid false negative results. At the 1-5 micrograms l-1 level of urinary DES, the average recovery of 2 micrograms l-1 DES-2H6 is 70 +/- 20% (s.d.).

Animals↗

PubMed1985

[A quarter of a century of studies of the abuse of hormonal anabolics in slaughtering animals: no DES-illusion!].

Over twenty-five years of analytical chemical and analytical biological forensic examination for residues of anabolic agents are reviewed. Up to 1981, this review is not only representative of the research done at the National Institute of Public Health but also of any research in this field in The Netherlands. A more detailed background is presented of the situation and the model of investigation adopted in the analytical-chemical testing of bovine urine for diethylstilbestrol (DES) following legal verdicts in 1981. At the time, examination in accordance with the Meat Regulations as well as a particular method of analysis were condemned. A retrospective study showed the rejected radioimmunochemical method (RIA) to be reliable as regards false-positive results at a level of 2 micrograms or more of DES per litre of urine (2 parts per billion or 2 ppb) rather than the level of 1 ppb adopted in 1981. Extensive and large-scale screening for DES from 1984 up to the present day resulted in the almost complete disappearance of the illegal use of this anabolic compounds in the Netherlands. However, investigations of sites of injection detected in slaughtered cattle during the period from 1983 to 1984, showed that other anabolics were still being used illegally. These studies particularly revealed residues of combined anabolic compounds ('cocktails'). The most common active anabolic ingredients observed were the xenobiotic steroids nortestosterone (nandrolone) and medroxyprogesterone and the exogenous natural steroids oestradiol and testosterone.

Anabolic Agents↗

PubMed1983

Identification and quantification of diethylstilbestrol in the urine of cattle by both low and high resolution gas chromatography mass spectrometry.

A confirmation method which can be used in regulatory screening programs for diethylstilbestrol in the urine of cattle is presented. trans-Diethylstilbestrol is purified from urine by Sep-Pak extraction and high-performance liquid chromatography and converted into its trimethylsilyl derivative. Identification is based on both accurate mass measurement of the molecular ion of trans-diethylstilbestrol trimethylsilyl by gas chromatography high resolution mass spectrometry and determination of the [M + 1] +/[M]+ peak height ratio by selected ion monitoring in low resolution. Specificity is such that on the basis of mass spectrometric data alone, all molecular formulae except those of diethylstilbestrol trimethylsilyl and only one other compound can be excluded. Additional specificity is provided by chromatographic data. The quantification is based on the standard addition method. The average recovery of trans-diethylstilbestrol is 76% with a standard deviation of 18% (n = 23).

Animals↗

PubMed1981

Isotope dilution mass spectrometry of cholesterol in serum.

Isotope dilution mass spectrometry is one of the best candidates for reference and definitive methods for the quantitative measurement of organic compounds. In this study sources of error were investigated. Where possible they were removed, and commercially available equipment had to be modified. The method was applied to the measurement of serum cholesterol. The precision is optimized and in the order of 0.5%. The mean of the recoveries of three measurements is 99.8%. The accuracy of the mean of three measurements is 0.2% if no interferences are present in the gas chromatographic mass spectrometric measurements.

Cholesterol↗

PubMed1978

The detection and identification of unknown halogenated compounds in environmental samples.

A new method is described in which the mass spectrometer is an element specific detector for a gas chromatograph. The elements investigated in this study are F, Cl, Br, J, S and N, but the method might be applied to other elements as well. The molecules coming from the gas chromatograph are atomized in a microwave induced discharge, located in the interface between the gaschromatograph and the mass spectrometer. Unknown compounds containing specific elements can be detected and their retention times can be determined. The method is applied to samples of surface water, fat of a grebe and human adipose tissue for halogenated compounds. Unknown halogenated compounds were found. A number of them were identified in samples of surface water.

Adipose Tissue↗

PubMed1978