A gas chromatographic/mass spectrometric screening, confirmation, and quantification method for estrogenic compounds

Quantitative screening of stilbenes and zeranol and its related residues and natural precursors in veal liver by gas chromatography-mass spectrometry

An existing gas chromatography-mass spectrometry-based quantitative screening method for the regulatory analysis of the resorcylic acid lactones zeranol, taleranol, and zearalanone and the stilbene anabolic steroids diethylstilbestrol and dienestrol was extended to include natural precursors of zeranol (zearalenone, alpha-zearalenol, and beta-zearalenol) in veal liver. No changes in sample preparation were required; the instrumental conditions were selected to effect a suitable chromatographic separation and detection of the analytes. Validation experiments were performed to verify the performance and applicability of the extended method for the quantitative screening of the original and additional analytes in veal liver in the concentration range from 0.5 to 2.0 microg/kg. The limits of detection were 0.08-0.19 microg/kg. The limits of quantitation were 0.27-0.64 microg/kg. Recoveries were 29-67%. Combined relative measurement uncertainty estimates were 6-21%.

Analytical methods for the determination of zeranol residues in animal products: A review

Analytical methods for zeranol residues are reviewed. Zeranol was a widely used as an anabolic promoter, and it could give rise to very low residues in the edible tissues of food animals. Zeranol was officially banned in Europe due to safety concerns because of its potential carcinogenic and endocrine-disrupting biological activity. A few analytical methods for determination of zeranol are reported in the literature and most of the methods such as thin-layer chromatography (TLC), gas chromatography-mass spectrometry (GC/MS), high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC/MS) and immunoassay are reviewed in this paper. Specific aspects of analysing zeranol such as sample selection, sample handling, method selection and chromatographic conditions are discussed. The instrumental methods such as LC/MS and GC/MS provide sensitive and specific techniques, but are very laborious and expensive. These methods are suitable for confirmation but not for screening of large numbers of samples. A rapid, sensitive and specific assay is needed to detect positive samples in routine analysis, and immunoassay offers practical advantages over the conventional instrumental methods in rapid analysis of zeranol residues. Immunochemical methods such as enzyme-linked immunoabsorbant assay (ELISA) are simple, rapid and cost-effective, with adequate sensitivity and specificity to detect small molecules. This review can be considered as a basis for further research aimed at identifying the most efficient approaches for the analysis of zeranol.

Improvement in steroid screening for doping control with special emphasis on stanozolol

The Medical Commission of the International Olympic Committee forbids the use of anabolic androgenic steroids and beta2-agonists to improve athletic performance. In this work we have selected examples of anabolic androgenic compounds and their metabolites to evaluate the GC-MS analysis of some trimethylsilyl derivatives. The aim is to set the best GC conditions to improve the detection within the whole range of analyte elution temperatures. The initial column temperature was changed to 105 or 140 degrees C followed by 40 degrees C min(-1) to 200 degrees C and then 15 degrees C min(-1) to 300 degrees C. Using 140 degrees C as the initial oven temperature it was possible to obtain narrower initial analyte distributions for the compounds that elutes at the beginning of the chromatogram as clenbuterol, mabuterol, epimethylenediol and norandrosterone, without loss of derivatized metabolites signal. Later. eluting analytes, such as the stanozolol metabolites, furazabol and oxandrolone were not affected. Temperatures below 140 degrees C. resulted in partial derivatization for some analytes mainly stanozolol related structures. Therefore evaluation of derivatization conditions as occurring in three steps, the vial, vaporization chamber and capillary column, was thoroughly assessed. The new program temperature improves the signal-to-noise ratio for some compounds and shows adequate resolution for endogenous compounds. Some of the difficult key separations necessary for doping control enforcement were also obtained with the proposed method.

Ultra trace detection of a wide range of anabolic steroids in meat by gas chromatography coupled to mass spectrometry

The control on use of anabolic agents in meat producing animals is generally based on urine, faeces or hair analysis. This exercise, which is usually performed in slaughterhouses or on farms, is not relevant to imported carcasses or retail meat. A single sensitive method for a wide range of anabolic steroids was developed. After extraction of the lyophilised meat, enzymatic hydrolysis was used for deconjugation. Solid-phase extraction on a polymeric stationary phase was performed prior to hydrolysis of ester residues under alkaline conditions. Liquid-liquid partitioning was used to separate the analytes into two main categories: phenol containing molecules, such as phenolic steroids, resorcylic acid lactones and stilbenes, and delta4-3-one containing molecules, such as most androgens and progestagens. Solid-phase extraction on silica columns was performed before applying a specific derivatisation for each compound sub-group. The combination of high-resolution chromatography with a quadrupole mass spectrometer permitted detection of 23 steroids in the 5-100 ng/kg range. Ion chromatograms for residue positive samples are shown and discussed.

Simultaneous determination of anabolic and catabolic steroid hormones in meat by gas chromatography-mass spectrometry

A rapid and economical method for the determination in meat of androgens, estrogens, progestogens and corticoids, including some precursors and metabolites, has been developed. The extracted steroids are separated in a polar, a neutral, and a phenolic fraction by C8-SPE followed by a liquid-liquid extraction of the phenolates. Each fraction is separately purified by normal-phase SPE. The different steroid fractions can be analysed either together to obtain a comprehensive hormone pattern in one step or separately to enhance detection selectivity and sensitivity. Using a universally applicable silylation of the hydroxyl and keto groups, detection limits of 0.02-0.1 microg/kg are reached by GC-MS (EI) in the selected ion monitoring mode.

Thin-layer chromatographic detection of zeranol and estradiol in fortified plasma and tissue extracts with Fast Corinth V

In an attempt to improve sensitivity of thin-layer chromatographic (TLC) analysis and selectivity of visualizing agents for detection of estrogenic anabolic hormones, several dyes were screened for their chromogenic interactions with estrone, estradiol, diethylstilbestrol (DES), zeranol (zearalanol), zearalanone, and mycotoxins, zearalenone and zearalenol. Fast Corinth V salt was selected for its relatively high sensitivity. These anabolic compounds were separated by TLC and visualized with Corinth V and the results compared to iodine and starch visualization. Fortified bovine plasma and tissues (kidney, liver and muscle) and chicken muscles were analyzed after a clean-up procedure using solid-phase dual columns of alumina and anion-exchange resin. Iodine-starch clearly detected 4 ng of estradiol and DES while zeranol and zearalenone were detected at higher levels (10 ng). Fast Corinth V showed distinct spots with 2 ng of zeranol and 4 ng of zearalenone while faint spots were observed with estradiol and estrone standards. DES was not detectable at these levels. Less background interference was observed with Corinth V than with iodine-starch. The former confirmed spots detected by iodine-starch. This study suggests its selectivity for detection of zeranol and its metabolite, zearalanone, in the presence of steroidal compounds.

Rapid screening method for the determination of diethylstilbestrol in edible animal tissue by column liquid chromatography with electrochemical detection

A rapid and sensitive screening method for the determination of residues of diethylstilbestrol in edible animal tissue is described. The analyte was extracted from the tissue with tert.-butyl methyl ether, reextracted with 1 M sodium hydroxide and further cleaned up by solid-phase extraction with C18 cartridges. Analysis was performed by isocratic elution with a phosphate-buffered mobile phase, methanol-0.05 M phosphate buffer pH 3.5 (67:33), on a Nucleosil 5-microns C18 column with electrochemical detection at +0.90 V. The average recovery of trans-diethylstilbestrol in spiked samples is 66%, with a standard deviation of 14% (n = 22) in the range 0.5-2.0 microgram/kg. The detection limit is 0.1-0.2 microgram/kg, although at this level other compounds may interfere and give rise to false positive results.

Determination of zeranol and beta-zearalanol in calf urine by immunoaffinity extraction and gas chromatography-mass spectrometry after repeated administration of zeranol

A method for the determination of zeranol and its metabolite beta-zearalanol in bovine urine is described. It has been applied to samples from calves given multiple subcutaneous doses of zeranol. Samples were extracted with immunoaffinity columns containing antibodies raised against zeranol and were analysed by gas chromatography-mass spectrometry. The immunoaffinity columns were prepared by coupling immunoglobulin G fractions obtained from rabbit antisera with a Sepharose matrix. The immunizing agent was carboxybutylzeranol coupled to bovine serum albumin. Gas chromatography-mass spectrometry was performed in the negative-ion chemical ionization mode, after derivatization of the compounds to their pentafluorobenzyl ethers, and allowed detection of analytes with a sensitivity of 0.01 ppb in spiked urine. The derivatization method and the gas chromatographic determination were also applied to the similar compounds zearalanone, zearalenone and beta-zearalenol. A synthesis of dideuterated zeranol and beta-zearalanol by isotopic exchange is described. These deuterated analogues had an isotopic purity of more than 99% and were used for quantitation of zeranol and beta-zearalanol by isotope dilution mass spectrometry. The recoveries of zeranol and beta-zearalanol, using the immunoaffinity columns, were determined after extraction from spiked urine and were 84 and 64%, respectively. The urines of treated calves were collected for several days after treatments and were analysed after hydrolysis with beta-glucuronidase and arylsulphatase. The samples showed variable but generally decreasing concentrations of zeranol and beta-zearalanol. The levels of beta-zearalanol ranged from less than 0.01 to 98 ppb and were 1.2-3.2 times higher than those of zeranol.

Derivatization and gas chromatographic-mass spectrometric detection of anabolic steroid residues isolated from edible muscle tissues

A method was developed for the detection of anabolic steroid residues in edible muscle tissues. After enzymic digestion of the tissue and purification on disposable C18 solid-phase extraction columns, the extract was injected onto a C18 reversed-phase high-performance liquid chromatographic column. Three fractions or windows were collected, each containing specific analytes. After evaporation to dryness, the residues were subjected to a derivatization procedure which yielded suitable derivatives. After gas chromatographic-mass spectrometric analysis, both gas chromatographic retention data and mass spectral data were used for the detection and identification of nortestosterone, testosterone, estradiol, ethinylestradiol, trenbolone, methyltestosterone, chlormadinone acetate, medroxyprogesterone acetate and megestrol acetate.

Determination of dexamethasone in bovine tissues by coupled-column normal-phase high-performance liquid chromatography and capillary gas chromatography-mass spectrometry

A new method for the determination of dexamethasone in bovine liver and muscle tissues has been developed. Crude tissue extracts were obtained by means of a three-phase liquid-liquid extraction scheme. The resulting residue was subjected to coupled-column normal-phase high-performance liquid chromatography which served to isolate the drug for the purpose of screening and quantification. Sample was injected onto the first column of the system, a phenyl column, from which a heart-cut was diverted to a short silica column which retained dexamethasone. The contents of this column were backflushed onto a cyanopropyl column which isolated dexamethasone. Mobile phases consisted of hexane modified with 2-propanol, acetic acid, and water. Analysis of each sample was completed in 15 min. Quantitation was performed by external standard calibration of ultraviolet response at 239 nm. Limits of detection were estimated to be 4 and 6 ppb in muscle and liver, respectively. In addition to screening and quantitation, the coupled-column system purified tissue extracts for gas chromatographic-mass spectrometric analysis which, in the selected-ion monitoring mode, confirmed the identity of the trimethylsilyl-enol-trimethylsilyl derivative of dexamethasone.

Analysis of diethylstilbestrol, dienestrol and hexestrol in biological samples by immunoaffinity extraction and gas chromatography-negative-ion chemical ionization mass spectrometry

A method has been developed for the detection of diethylstilbestrol, together with dienestrol and hexestrol, using extraction with a single immunoaffinity column containing antibodies raised against diethylstilbestrol, followed by gas chromatography-negative-ion chemical ionization mass spectrometry. Immunoaffinity columns were prepared by coupling immunoglobulin G fractions obtained from rabbit antisera with a Sepharose matrix. The immunizing agent was synthesized by introducing a carboxyl group into the diethylstilbestrol molecule and coupling this product to bovine serum albumin. The columns were used for immunoadsorption of diethylstilbestrol and other estrogens, after dilution of samples with phosphate buffer, and were eluted with acetone-water (95:5 v/v). A derivatization method suitable for gas chromatographic-mass spectrometric analysis of diethylstilbestrol and other estrogens was developed using pentafluorobenzyl bromide and ethanolic potassium hydroxide as reagents. The derivatives obtained were detectable at the sub-picogram level using gas chromatography with negative-ion chemical ionization mass spectrometry. Recoveries of cis- and trans-diethylstilbestrol, dienestrol and hexestrol from the immunoaffinity columns, determined after extraction from urine, plasma and buffer, ranged from 28 to 96%. The sensitivity for diethylstilbestrol in urine samples was ca. 10 ppt. The method was applied to the analysis of urine from calves given a single dose of 10 mg of diethylstilbestrol. Free and glucuronic acid conjugated diethylstilbestrol decreased with time, but their ratio was variable.

Metabolism of some anabolic agents: toxicological and analytical aspects

The metabolism of the animal growth promotants diethylstilbestrol, zeranol and 17 beta-trenbolone and of a few anabolizing steroids used in humans is briefly reviewed. The possible role of reactive metabolic intermediates in the toxicity of some anabolic agents is discussed. Analytical implications of the metabolism of anabolizing agents are described and examples of the analysis of metabolites by means of recently developed techniques are given. It is proposed to utilize the covalent binding of reactive metabolites of anabolic compounds to blood proteins such as haemoglobin and serum albumin for retrospective doping analysis.

Profiling of free and conjugated [3H]zeranol metabolites in pig plasma

Extraction and high-performance liquid chromatographic (HPLC) procedures are described that permit the complete analysis of free and conjugated zeranol metabolites in plasma from pigs implanted with [3H]zeranol. Free metabolites (9.0%) are extracted and then analysed by radio-HPLC on a reversed phase C18 column. They are distributed between three compounds that have been identified by gas chromatography-mass spectrometry as taleranol, zeranol and zeralanone. Direct radio-HPLC of the pre-extracted, deproteinated and Sep-Pak C18-purified plasma on a reversed-phase C18 column using tetrabutylammonium as an ion-pairing agent showed four main peaks: one corresponds to a weakly retained unidentified compound(s) (20%) and the other three were identified as the taleranol, zeranol and zeralanone glucuro conjugates. However, the total recovery is only about 25% owing to strong affinity of this polar material for the plasma proteins. Enzymatic deconjugation of the pre-extracted plasma followed by radio-HPLC analysis of the freed metabolites led to a good recovery of the radioactivity (81.8%) and allowed the quantitation of the different metabolites. These preliminary results indicate that zeranol is metabolized in the pig following pathways similar to those in other tested species.

Determination of melengestrol acetate in bovine tissues by automated coupled-column normal-phase high-performance liquid chromatography

A method has been developed for the determination of melengestrol acetate in bovine tissues at lower levels than previously reported. Liquid-liquid extraction of tissue homogenates provided crude clean-up while final isolation, screening, and quantification was done on-line with an automated, normal-phase, coupled-column high-performance liquid chromatographic system. The chromatographic system included phenyl and silica analytical columns for the purposes of isolation and final separation, respectively. These columns provided a large difference in selectivity when operated under normal-phase conditions which allowed for the efficient isolation of melengestrol acetate from the complex tissue extracts. Mobile phases were composed of hexane and dichloromethane modified with methanol and water. Transfer and enrichment of the analyte from the primary phenyl column to the silica column was via a short (12 mm x 4 mm I.D.) silica column. Regeneration and equilibration of the phenyl column was performed after the injection of each tissue extract and was accomplished simultaneously while analytical separation occurred on the final silica column. Routing of the mobile phases and regeneration solvent was performed with automated switching valves. The total time required for each analysis was 12 min. Quantification is demonstrated using external standards with UV detection at 287 nm. The overall recovery of the method was 86% with a coefficient of variation of 9.84% at the 10 ppb [the American billion (10(9] is used in this article] level in bovine liver extracts.