W.A. Traag

Determination of aflatoxins in cattle feed by liquid chromatography and post-column derivatization with electrochemically generated bromine

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Procedure for the gas chromatographic-mass spectrometric confirmation of some exogenous growth-promoting compounds in the urine of cattle

As gas chromatography-mass spectrometry is the most conclusive confirmation technique available today for the detection of ppb levels of anabolics in the urine of cattle, the following procedure was used. The urine is hydrolysed with Helix pomatia intestinal juice, extracted, and the extract cleaned by gel-permeation chromatography or with Extrelut. In one fraction are eluted diethylstilboestrol, dienoestrol, hexoestrol, methyltestosterone, ethinyloestradiol, zeranol and trenbolone. This fraction is injected into a two-dimensional high-performance liquid chromatography system. From the first column, the fraction containing the above-mentioned compounds is transferred to the second column, where a separation into two fractions is obtained. The first fraction contains zeranol and trenbolone, the second fraction the stilbenes, methyltestosterone and ethinyloestradiol. In general, the compounds are derivatized with an N,O-bis (trimethylsilyl)trifluoroacetamide-trimethylchlorosilane mixture to a trimethylsilyl derivative. With stilbene, confirmatory derivatization into heptafluorobutyryl derivatives is necessary. In combination with a Finnigan 4000/INCOS system, a CP-Sil-5 CB and a CP-Sil-19 CB capillary are used for final confirmation. Two capillaries with different polarities are necessary to overcome problems with possible interferences from compounds extracted from the urine. Recoveries at the ppb level are better than 80%.

Problems encountered in the determination of 2,3,4-2'4'5' hexachlorobiphenyl (CB 138) in environmental samples

Abstract Selected individual chlorobiphenyls (CB) used for monitoring and tolerance purposes are checked on interferences using negative chemical ionization (NCI) mass spectrometry. An interference at the retention time of CB 138 (2,3,4-2′4′5′ hexachlorobiphenyl) was found. Quantitative results reported up till now and maximum residue limits (MRL) set for this compound are at least questionable.

Simultaneous determination of planar chlorobiphenyls and polychlorinated dibenzo-p-dioxins and -furans in Dutch milk using isotope dilution and gas chromatography—high-resolution mass spectrometry

A method is described for the simultaneous determination of planar chlorobiphenyls and dioxins in milk using isotope dilution and gas chromatography-high-resolution mass spectrometry (GC-MS). The method is based on gel permeation chromatography, alumina clean-up and carbon chromatography and is highly automated, making a high sample throughput possible. Data on recovery, accuracy and reproducibility of results obtained with quality control samples are presented. Data for both dioxins and planar chlorobiphenyls from the analysis of samples of Dutch milk from several areas in the Netherlands are also presented. Possible interference of the chlorobiphenyls in the determination of the dioxins in the GC-MS method is discussed.

Quantitative Determination of Specified Chlorobiphenyls in Fish with Capillary Gas Chromatography and its use for Monitoring and Tolerance Purposes

A gel permeation (GPC) clean-up procedure of fish samples in combination with capillary gas chromatography is used for the determination of individual chlorobiphenyls. The described method is compared with a more universal method based on saponification. Starting from a tolerance for PCBs expressed as a technical Aroclor, tolerance for some specified individual chlorobiphenyls are derived. It is shown that these tolerances for specified individual chlorobiphenyls can be used for monitoring and tolerance purposes. Rejection obtained with the Dutch PCB tolerance agree with rejections obtained with individual tolerances.

Identification and determination of metabolites in plant cell biotechnology by gas chromatography and gas chromatography/mass spectrometry : Application to Nonpolar Products of Chrysanthemum cinerariaefolium and Tagetes Species

Abstract Gas-liquid chromatography (g.l.c.) and gas-liquid chromatography/mass spectrometry (g.c./m.s.) were used for profile analysis and for identification, confirmation and determination of traces of nonpolar metabolites synthesized in plant tissue, calli and in suspension-cultured cells of Chrysanthemum cinerariaefolium (pyrethrum) or Tagetes species (marigold). When dried leaf samples (1–20 mg) were tested, six pyrethrins were detected simultaneously at the picogram level with an electron capture detector. This method permits the early selection of high yielding tissues and calli for the development of plant cell cultures. α-Terthienyl was quantified at the nanogram level with the electron capture detector; calibration graphs were linear between 0.2 and 20 ng and the minimum detectable quantity was about 0.1 ng. The concentration of α-terthienyl in air-dried roots of T. erecta was 140 μg g −1 . However, this procedure used alone is not reliable, because α-terthienyl and the pyrethrin Cinerin I have the same retention time. Mass spectrometry is needed for identification and confirmation. Profile analysis of a leaf extract of T. minuta by high-resolution g.c./m.s, and accurate mass measurements showed 13 nonpolar compounds, of which 9 were tentatively identified; they include 2 sesquiterpenoids, 3 thiophenes, 2 sterols with a precursor and ethyl linolenate. Analyses of T. minuta indicated that in calli and cell suspensions, plant sterols are synthesized but sesquiterpenoids or thiophenes are not produced.

Automated clean-up procedure for the gas chromatographic-high-resolution mass spectrometric determination of polychlorinated dibenzo-p-dioxins and dibenzofurans in milk

A highly automated extraction and clean-up method for polychlorinated dibenzodioxins and polychlorinated dibenzofurans is described. The method includes the use of gel permeation chromatography, alumina clean-up and porous graphitized carbon chromatography, followed by analysis by gas chromatography-high-resolution mass spectrometry. The procedure allows for the analysis of six milk samples per day in addition to two quality control samples and a blank. Detection limits on a fat basis for the individual congeners in milk samples are in the sub-ppt range. Long-term performance was investigated and data are given for reproducibility, precision and accuracy.

Confirmatory analysis of clenbuterol using two different derivatives simultaneously

To meet the requirements of the European Community for confirmatory analysis of clenbuterol using low-resolution mass spectrometry, usually two different techniques (i.e. electron impact and chemical ionization) have to be applied to confirm unambiguously its presence in extracts of urine. This paper describes the application of two different derivatives and the simultaneous analysis of these two different derivatives in one gas chromatographic-mass spectrometric analysis. With the proposed combination of techniques, Community requirements can more easily be met in only one analytical run. Examples of the analysis of some urine samples are presented, as well as data on linearity, repeatability and equivalence of the combined technique to separate determinations.

Tandem capillary gas chromatography in pesticide residue analysis

Maximum residue levels of pesticides in food and feed are often below the 0.1 ppm level. On capillary columns, the maximum injection volumes are 5-10 microliters in the splitless mode, although of course some (acceptable) overloading of the GC column occurs. Injection of larger volumes (up to 100 microliters) is possible only when the solvent can be removed whilst at the same time the compounds of interest are concentrated in a small zone. The advantage of such a procedure is obvious: the limit of detection is improved by a factor of 10-20, so a concentration step can be omitted. A Chrompack MUSIC (MUltiple Switching Intelligent Controller) kit was connected with a Tracor 550 gas chromatograph with an electron-capture detector for chlorinated compounds. Data are presented that show that gel permeation chromatography on Bio-Beads SX-3 as a clean-up medium in combination with MUSIC allows the detection of sub-ppm levels of organochlorine pesticides in grains, fats and vegetables by splitless injection of a 100-microliters sample on to the chromatographic column.

Determination of individual chlorinated biphenyls in agricultural products by automated capillary gas chromatography : Determination in cattle feed and its relation to milk residues

Polychlorinated biphenyls were determined by glass capillary gas chromatography with electron capture detection, with automatic splitless injection. Using a saponification step as clean-up procedure, the detection limit for individual polychlorinated biphenyls can be improved up to the sub-ppb level for vegetable material and up to the ppb level for fatty material. Quantification is carried out by comparison of separated chlorobiphenyl peaks with the corresponding individual chlorobiphenyl standards. The results of monitoring programs of milkfat and cattle feed are summarized. Accumulation factors for several chlorobiphenyls, determined in an experiment with lactating cows, are used to show that contamination of the milkfat is not caused by contaminated cattle feed.