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H J Stan

Publications and source records attributed to H J Stan.

26 records · Page 2Linked to original sources
PubMed1979

[Determination of trenbolone and testosterone residues in meat by high pressure liquid chromatography (author's transl)].

A new method for the qualitative and quantitative determination of trenbolone and testosterone residues in meat, liver, and kidney is described. The analytical procedure consists of the following steps: homogenisation of the meat sample with tetrahydrofurane; liquid-liquid partition first between acetonitrile and hexane, then between sodium hydroxide and petroleum ether/benzene; purification of a silica gel column. The purified sample is analysed by high pressure liquid chromatography using silica gel packings. Detection and quantitative determination are performed with a fluorescence and/or a spectrophotometric detector. Fluorescence measurements are carried out applying a self-made silica gel packed flow-cell. The detection limit in meat extracts is 50 ppb for testosterone and 5 ppb for trenbolone.

Animals↗
PubMed1978

[Detection of trenbolone residues in meat by thin layer chromatography and fluorimetry (author's transl)].

An new method for the qualitative and quantitative determination of trenbolone residues in meat, liver and kidney is described. The analytical procedure consists of the following steps: comminution of the meat sample; homogenisation with tetrahydrofurane; liquid-liquid partition first between acetonitril and hexane then between sodium hydroxide solution and petroleum ether/benzene; chromatography on a silica gel column. The detection on the TLC-plate is performed with 366 nm ultra violet light. The quantitative determination is carried out by means of a remission spectral fluorimeter directly on the plate. The detection limit in meat extracts was 5 ppb.

Animals↗
PubMed1978

[Detection of estrogen residues in meat by thin layer chromatography and fluorimetry (author's transl)].

A new method for the qualitative and quantitative determination of six anabolic substances is described. The analytical procedure consists of the following steps: comminution of the meat sample; homogenisation with tetrahydrofurane; liquid-liquid partition between sodium hydroxide solution and petroleum ether/benzene; chromatography of the estrogen containing fraction on Sephadex LH-20; derivatization with Dansyl chloride; and finally thin layer chromatography. The qualitative estimation on the TLC-plate is performed with 366 nm ultra violet light. The quantitative determination is carried out either by fluorimetry after elution of the substances from the plate, or by means of a remission spectral fluorimeter directly on the plate. The detection limit of the qualitative estimation in meat extracts was 5--10 ppb. A minimum concentration of 20--50 ppb is necessary for quantitative determination.

Animals↗
PubMed1977

[Detection of organophosphorous pesticide residues in food at the ppb level with open tubular column gas chromatograph-mass spectrometry (author's transl)].

The application of the combination open tubular column gas chromatography-mass spectrometry-computer for the detection and identification of organophosphorous pesticide residues in food was demonstrated. 23 of the most frequently used organophosphorous pesticides in Germany were separated on a 20 m SE-54 glas capillary column with the exception of the pair phosphamidone/fenchlorphos. Detection and identification of the individual pesticides were performed by chemical ionization mass spectrometry (CI) with isobutane and computerized background subtraction. In an example 10 of these substances were detected in cherries at a residue level of 0.45 ppm by comparison of CI mass spectra.--Mass fragmentography with single and multiple ion detection allowed the unequivocal identification of these 10 pesticides at the 40 ppb level in cherries. The detection limit of the pesticides examined in this study was found in the lower ppb region in food extracts using CI with isobutane. The application of an integrated computer system allowed the determination of all 10 pesticides in a single gc run.--Comparing electron impact and chemical ionization with isobutane in mass fragmentography of organophosphorous pesticide residues in food a considerable lower detection limit was observed using the chemical ionization procedure.

Chromatography, Gas↗
PubMed1975

[Determination of zeranol in meat (author's transl)].

A qualitative and quantitative method for the determination of zeranol in meat and liver is described. The analysis procedure includes methanol extraction, enzymatic hydrolysis of possibly existing conjugates, and liquid-liquid partition, followed by two-dimensional thin layer chromatography. Zeranol is selectively made visible as a red-violet spot with Fast Blue B salt. The detection limit in meat is found to be 10 ppb. For the quantitative determination zeranol is eluted from the TLC plates and reacted with Fast Blue B salt. A quantitative determination can be performed with a concentration of 0.4 ppm. The application of this method demonstrated the presence of zeranol in 2 out of 18 commercially obtained samples.

Chemical Phenomena↗
PubMed1975

Conversion of linoleic acid hydroperoxide by soybean lipoxygenase in the presence of guaiacol: identification of the reaction products.

Linoleic acid hydroperoxide formed by soybean lipoxygenase was metabolized by the same enzyme in the presence of guaiacol. The products of this reaction included, trihydroxyoctadecenoic acids, hydroperoxydihydroxyoctadecenoic acids, hydroxyepoxyoctadecenoic acids, dihydroxyoctadecenoic acids, hydroxyoctadecadienoic acids, and oxooctadecadienoic acids.

Guaiacol↗
PubMedDate not supplied

In vitro metabolism of the anabolic drug zeranol.

The anabolic drug zeranol, which is employed for livestock breeding was studied for its metabolic fate in vitro using isolated microsomal preparations from bovine liver, uterus, and muscle. Diethylstilbestrol and 17 beta-estradiol were investigated simultaneously for comparison. The structure of the zeranol metabolite was examined by means of TLC as well as GC-MS analysis. A sensitive color reaction after two-dimensional TLC described earlier for zeranol determination in veal samples is proposed for the detection of the zeranol metabolite zearalanone and the mycotoxin zearalenone. The estrogenic activity of the three mycoestrogens, understood as their binding capacity to the cytoplasmic estrogen receptor protein from bovine uterus, is measured using the estrogen receptor test. The data suggest that zeranol is biotransformed in vitro to a less active estrogen which has a marked similarity to the mycotoxin zearalenone. Further investigations are necessary to quantitate the biotransformation in vitro as well as to evaluate the toxicity of the drug metabolite.

Animals↗