Determination of Semicarbazide in Fresh Egg and Whole Egg Powder by Liquid Chromatography/Tandem Mass Spectrometry: Interlaboratory Validation Study

An interlaboratory validation study was conducted according to harmonized protocols to evaluate the effectiveness of a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of semicarbazide (SEM) in fresh whole egg and in an industrially processed whole egg powder. The sample was extracted with hydrochloric acid and derivatized with 2-nitrobenzaldehyde, with 1,2-[15N213C]SEM as the internal standard. The extract was neutralized and purified on a solid-phase extraction cartridge. SEM was determined by reversed-phase LC with detection by MS/MS. Five fresh egg samples, of which 3 were obtained from hens fed nitrofurazone (NFZ), one was spiked with SEM at 50 μg/kg and one was a blank sample, and 5 industrial whole egg powder samples, of which 3 were spiked with fresh whole egg from hens fed NFZ, one was spiked with SEM at 350 μg/kg, and one was a blank sample, were sent to 15 laboratories in 10 different European countries. Results were obtained from 12 participants. Average recoveries of SEM from the fresh egg and the egg powder samples were 105.3 and 121.3%, respectively. The relative standard deviation for repeatability (RSDr) ranged from 2.9 to 9.3%, and the relative standard deviation for reproducibility (RSDR) ranged from 22.5 to 38.1%. The method showed acceptable within- and between-laboratory precision for both matrixes, as evidenced by the HorRat values, at the target levels for the determination of SEM.

Determination of Semicarbazide in Baby Food by Liquid Chromatography/Tandem Mass Spectrometry: Interlaboratory Validation Study

An interlaboratory validation study funded by the European Commission, Directorate General for Health and Consumer Protection (DG SANCO), was conducted to evaluate the effectiveness of a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of semicarbazide (SEM) in different types of baby food at a possible future European regulatory limit (10 ng/g). The test portion of the sample was extracted with hydrochloric acid, and the analyte was derivatized with 2-nitrobenzaldehyde, with 1,2-[15N2, 13C] SEM as an internal standard. The extract was neutralized and then purified on a solid-phase extraction cartridge. The SEM was determined by reversed-phase LC with detection by MS/MS. Apple puree, rice pudding, and meat/vegetable meal baby food materials, spiked with SEM at levels of about 3, 10, and 30 ng/g, respectively, were sent to 20 laboratories in 12 different European countries, which submitted results from 17 participants. Recoveries ranged from 88.8 to 106.1%. Based on results for spiked samples (blind pairs at 3 levels), the relative standard deviations for repeatability (RSDr) ranged from 4.2 to 6.9% and the relative standard deviations for reproducibility (RSDR) ranged from 16.6 to 24.3%. The method showed acceptable within- and between-laboratory precision for all 3 matrixes, as evidenced by HorRat values, at the target levels for the determination of SEM.

Development of a strategy for the quantification of food allergens in several food products by mass spectrometry in a routine laboratory

Worldwide, mass spectrometry is widely used to detect and quantify food allergens, especially in complex and processed food products. Yet, the absence of a regulatory framework for the developed methods has led to a lack of harmonization between laboratories. In this study, ten allergens were analyzed in eight food products by UHPLC-MS/MS, in order to establish criteria for the retention time, variation tolerance, the ion ratio deviation, and the signal-to-noise ratio for allergen detection. The set of criteria should help laboratories to compare results and avoid false positives and negatives. Furthermore, a strategy combining standard addition and labeled peptide correction was used to quantify milk, soy, peanut, and egg allergens in eight food products. This strategy is particularly interesting for routine laboratories, which receive hundreds of samples and cannot use an external calibration curve for each sample.

Liquid chromatography coupled to tandem mass spectrometry for detecting ten allergens in complex and incurred foodstuffs

Food allergy is a considerable heath problem, as undesirable contaminations by allergens during food production are still widespread and may be dangerous for human health. To protect the population, laboratories need to develop reliable analytical methods in order to detect allergens in various food products. Currently, a large majority of allergen-related food recalls concern bakery products. It is therefore essential to detect allergens in unprocessed and processed foodstuffs. In this study, we developed a method for detecting ten allergens in complex (chocolate, ice cream) and processed (cookie, sauce) foodstuffs, based on ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Using a single protocol and considering a signal-to-noise ratio higher than 10 for the most abundant multiple reaction monitoring (MRM) transition, we were able to detect target allergens at 0.5mg/kg for milk proteins, 2.5mg/kg for peanut, hazelnut, pistachio, and cashew proteins, 3mg/kg for egg proteins, and 5mg/kg for soy, almond, walnut, and pecan proteins. The ability of the method to detect 10 allergens with a single protocol in complex and incurred food products makes it an attractive alternative to the ELISA method for routine laboratories.

Discrimination between Synthetically Administered and Endogenous Thiouracil Based on Monitoring of Urine, Muscle, and Thyroid Tissue: An in Vivo Study in Young and Adult Bovines

Thiouracil (TU), synthesized for its thyroid-regulating capacities and alternatively misused in livestock for its weight-gaining effects, is acknowledged to have an endogenous origin. Discrimination between low-level abuse and endogenous occurrence is challenging and unexplored in an experimental setting. Therefore, cows (n = 16) and calves (n = 18) were subjected to a rapeseed-supplemented diet or treated with synthetic TU. Significant higher urinary TU levels were recorded after TU administration (<CC_α, 15 642 μg L^-1) compared to rapeseed supplementation (<CC_α, 65.8 μg L^-1), however, with overlapping values. TU was not detected in the edible meat; however, concentrations between the CC_α and 10 μg kg^-1 were noted in thyroid tissue of calves and cows following rapeseed supplementation. The latter concentrations were significantly higher in thyroid tissue of calves (22.9-41.8 μg kg^-1) and cows (16.9-36.7 μg kg^-1) after synthetic TU administration. These results strongly point toward thyroid analysis as a discriminatory tool.

Advances in ultra-high performance liquid chromatography coupled to tandem mass spectrometry for sensitive detection of several food allergens in complex and processed foodstuffs

Sensitive detection of food allergens is affected by food processing and foodstuff complexity. It is therefore a challenge to detect cross-contamination in food production that could endanger an allergic customer's life. Here we used ultra-high performance liquid chromatography coupled to tandem mass spectrometry for simultaneous detection of traces of milk (casein, whey protein), egg (yolk, white), soybean, and peanut allergens in different complex and/or heat-processed foodstuffs. The method is based on a single protocol (extraction, trypsin digestion, and purification) applicable to the different tested foodstuffs: chocolate, ice cream, tomato sauce, and processed cookies. The determined limits of quantitation, expressed in total milk, egg, peanut, or soy proteins (and not soluble proteins) per kilogram of food, are: 0.5mg/kg for milk (detection of caseins), 5mg/kg for milk (detection of whey), 2.5mg/kg for peanut, 5mg/kg for soy, 3.4mg/kg for egg (detection of egg white), and 30.8mg/kg for egg (detection of egg yolk). The main advantage is the ability of the method to detect four major food allergens simultaneously in processed and complex matrices with very high sensitivity and specificity.

The Production of Polyclonal Antibodies in Laboratory Animals. The Report and Recommendations of ECVAM Workshop 35

This is the report of the thirty-fifth of a series of workshops organised by the European Centre for the Validation of Alternative Methods (ECVAM). ECVAM's main goal, as defined in 1993 by its Scientific Advisory Committee, is to promote the scientific and regulatory acceptance of alternative methods which are of importance to the biosciences and which reduce, refine or replace the use of laboratory animals. One of the first priorities set by ECVAM was the implementation of procedures which would enable it to become well informed about the state-of-the-art of non-animal test development and validation, and the potential for the possible incorporation of alternative tests into regulatory procedures. It was decided that this would be best achieved by the organisation of ECVAM workshops on specific topics, at which small groups of invited experts would review the current status of various types of in vitro tests and their potential uses, and make recommendations about the best ways forward (1). This joint ECVAM/FELASA (Federation of European Laboratory Animal Science Associations) workshop on The Immunisation of Laboratory Animals for the Production of Polyclonal Antibodies was held in Utrecht (The Netherlands), on 20-22 March 1998, under the co-chairmanship of Coenraad Hendriksen (RIVM, Bilthoven, The Netherlands) and Wim de Leeuw (Inspectorate for Health Protection, The Netherlands). The participants, all experts in the fields of immunology, laboratory animal science, or regulation, came from universities, industry and regulatory bodies. The aims of the workshop were: a) to discuss and evaluate current immunisation procedures for the production of polyclonal antibodies (including route of injection, animal species and adjuvant ); and b) to draft recommendations and guidelines to improve the immunisation procedures, with regard both to animal welfare and to the optimisation of immunisation protocols. This report summarises the outcome of the discussions and includes a number of recommendations and a set of draft guidelines (included in Appendix 1).

Preliminary study on the presence of prednisolone in porcine urine and liver - How to distinguish endogenous from therapeutically administered prednisolone

In animal breeding in Europe, synthetic corticosteroids are not allowed as growth-promoting agents. However, prednisolone residues have recently been found in porcine urine samples collected at slaughterhouses. The aim of this work was therefore to look for prednisolone in porcine urine and liver, to determine if detected residues might be of endogenous origin, and to check the possible relation with stress. An analytical method developed in-house was validated, combining immunoaffinity-based purification and ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). This method was applied to urine and liver samples collected from sows experimentally treated either with prednisolone or tetracosactide hexaacetate (synthetic analogue of ACTH). Thanks to the performance of the analytical method, both cortisol and prednisolone were detected in all pig urine samples collected before or after administration of prednisolone or tetracosactide hexaacetate. High levels of prednisolone were found in porcine urine just after prednisolone administration, decreasing quickly to within the range detected in non-treated animals. In urine, the cortisol level varied depending on the time lapse between administration and sampling. On the other hand, prednisolone was detected also in liver samples of treated pigs. In this matrix, the cortisol level remained constant and prednisolone/cortisol level could be used to detect prednisolone administration at least 4 days after injection. In conclusion, the best indicator for detecting illicit prednisolone administration to pigs seems to be the prednisolone/cortisol ratio in liver samples. This preliminary work must be confirmed by a larger-scale study and metabolites should also be included.

Validation of methods for the detection and quantification of engineered nanoparticles in food

The potential impact of nanomaterials on the environment and on human health has already triggered legislation requiring labelling of products containing nanoparticles. However, so far, no validated analytical methods for the implementation of this legislation exist. This paper outlines a generic approach for the validation of methods for detection and quantification of nanoparticles in food samples. It proposes validation of identity, selectivity, precision, working range, limit of detection and robustness, bearing in mind that each "result" must include information about the chemical identity, particle size and mass or particle number concentration. This has an impact on testing for selectivity and trueness, which also must take these aspects into consideration. Selectivity must not only be tested against matrix constituents and other nanoparticles, but it shall also be tested whether the methods apply equally well to particles of different suppliers. In trueness testing, information whether the particle size distribution has changed during analysis is required. Results are largely expected to follow normal distributions due to the expected high number of particles. An approach of estimating measurement uncertainties from the validation data is given.

Transfer of flubendazole and tylosin from feed at cross-contamination levels to various poultry matrices

Residues of veterinary drugs and feed additives used extensively in animal husbandry are sometimes found in edible matrices. In this study, broilers received experimental feed, containing either flubendazole or tylosin, at cross-contamination levels of 2.5%, 5%, and 10% of the therapeutic dose to determine the transfer ratio of these molecules from feed to poultry matrices. Breast and thigh muscle and liver samples were collected during treatment and depletion periods and then analyzed using liquid chromatography-tandem mass spectrometry. The parent molecule flubendazole and its 2 major metabolites were quantified. After 3 to 5 d, a plateau phase was reached, and a few days after withdrawal of the experimental feed, a depletion of residues was noted. Significant difference between both muscle types was noted for flubendazole. Strong metabolization of flubendazole in the liver was seen. For tylosin, no residue concentrations above the limit of quantification could be detected in muscle. None of the residue concentrations for either molecule exceeded the corresponding maximum residue limits.

Screening for the coccidiostats halofuginone and nicarbazin in egg and chicken muscle: development of an ELISA

Nicarbazin and halofuginone have been widely used as coccidiostats for the prevention and treatment of coccidiosis in poultry. It has been shown that accidental cross-contamination of feed can lead to residues of these compounds in eggs and/or muscle. This paper describes a direct competitive assay for detecting halofuginone and nicarbazin, developed as qualitative screening assay. In an optimized competitive ELISA, antibodies showed 50% binding inhibition at approximately 0.08 ng ml(-1) for halofuginone and 2.5 ng ml(-1) for dinitrocarbanilide (marker residue for nicarbazin). Extraction from the matrix was carried out with acetonitrile followed by a wash with hexane. The assay's detection capability (CCbeta) for halofuginone was < 0.5 microg kg(-1) in egg and < 1 microg kg(-1) in muscle. For dinitrocarbanilide, the CCbeta was estimated at < 3 microg kg(-1) in egg and < 10 microg kg(-1) in chicken muscle.

Incidence of residues of nine anticoccidials in eggs

A survey of the presence of residues of anticoccidials was performed. Three hundred and twenty egg samples, purchased in eight different European countries, were analysed for the presence of nine different compounds: dimetridazole, diclazuril, halofuginone, robenidine, nicarbazin, narasin, salinomycin, lasalocid and monensin. Analyses were performed by LC-MS/MS. Of the samples analysed, 114 (35.6%) contained one or more of the nine anticoccidials in concentrations ranging from 0.1 to 63 microg kg-1. Salinomycin and lasalocid account for more than 60% of all positive samples. Almost 90% of all positive samples contained less than 2 microg kg-1. Results were put into perspective of the farming method and country of origin.

Multi-allergen screening immunoassay for the detection of protein markers of peanut and four tree nuts in chocolate

A multiresidue enzyme immunoassay was developed to check for the presence of markers of peanut, hazelnut, almond, cashew and Brazil nuts in a single run. The assay was designed under the competitive indirect format and adapted for screening purposes applied to chocolate samples. The limit of detection for this assay was below 1 microg g-1 protein for each allergenic food. In most cases, the high specificity of the antibodies used allowed the identification of each particular allergenic food with no possible confusion. This assay was proven to be useful as part of an analytical procedure involving the identification of the unknown allergenic food among peanut and other tree nuts in recalled samples before the application of a quantitative technique to determine the level of cross-contamination.

Determination of halofuginone in eggs by liquid chromatography/tandem mass spectrometry after cleanup with immunoaffinity chromatography

A sensitive and very selective high-performance liquid chromatography/tandem mass spectrometric (LC/MS/MS) method for the detection of halofuginone in whole egg has been developed. After deproteinisation with acetonitrile and evaporation of the organic solvent, halofuginone was further isolated by applying immunoaffinity chromatography. The concentrated eluent was injected into the LC/MS/MS system on a C18 column. The precursor ion ([M+H]+) produced by positive electrospray ionisation was selected for fragmentation with argon. Validation parameters such as recovery, linearity and repeatability, decision limit (CCalpha) and detection capability (CCbeta) were determined.

Urinary 19-norandrosterone purification by immunoaffinity chromatography: application to gas chromatography/combustion/isotope ratio mass spectrometric analysis

The detection of exogenous 19-norandrosterone (19-NA) in urines was investigated by using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). 19-NA is, for the first time to our knowledge, isolated from urinary matrix by specific immunoaffinity chromatography (IAC) before analysis. The sample preparation consisted of a preliminary purification of urine by solid-phase extraction after hydrolysis by beta-glucuronidase. Unconjugated 19-NA was thus isolated by IAC and directly analysed by GC/C/IRMS. Optimisation of IAC purification was achieved and the reliability of the technique for anti-doping control is discussed.

Identification and quantification of five macrolide antibiotics in several tissues, eggs and milk by liquid chromatography-electrospray tandem mass spectrometry

We present an electrospray high-performance liquid chromatographic tandem mass spectrometric (HPLC-MS-MS) method capable of determining in several tissues (muscle, kidney, liver), eggs and milk the following five macrolides: tylosin, tilmicosin, spiramycin, josamycin, erythromycin. Roxithromycin was used as an internal standard. The method uses extraction in a Tris buffer at pH 10.5, followed by protein precipitation with sodium tungstate and clean-up on an Oasis solid-phase extraction column. The HPLC separation was performed on a Purospher C18 column (125 x 3 mm I.D.) protected by a guard column, with a gradient of aqueous 0.1 M ammonium acetate-acetonitrile as the mobile phase at a flow-rate of 0.7 ml min(-1). Protonated molecules served as precursor ions for electrospray ionisation in the positive ion mode and four product ions were chosen for each analyte for multiple reaction monitoring (MRM). A validation study was conducted to confirm the five macrolides by MRM HPLC-MS-MS analysis of a negative control and fortified samples. All of the samples analysed were confirmed with four ions. The ion ratio reproducibility limit ranged from 2.4 to 15%. All compounds could be detected and quantified at half-maximum residue limits (MRLs). The method is specific, quantitative and reproducible enough to conform to European Union recommendations within the concentration range 0.5 MRL-2 MRL (accuracy: 80 to 110%, relative standard deviation: 2 to 13%). This whole method allows extraction and analysis of up to 50 samples per day.

Determination of a method for detecting and quantifying azaperone, azaperol and carazolol in pig tissues by liquid chromatography-tandem mass spectrometry

A quick, simple method for quantifying carazolol, azaperol and azaperone is described. Liquid extraction was followed by a clean-up on an Oasis SPE cartridge. The analytes were separated by HPLC and analysed by MS-MS with atmospheric pressure chemical ionisation in the positive mode. The method was applied to muscle and kidney from untreated pigs, the samples being spiked with the three molecules of interest. Recovery was between 70 and 106%. Quantification parameters were also good: the accuracy was between 80 and 110% and the coefficient of variation did not exceed 16%, being below 8% for 90% of the samples. Linearity was good from MRL/4 to 2MRL. For unequivocal identification of each analyte, four ions were detected. The method proved very suitable for routine analysis.

Long-term detection of clenbuterol in human scalp hair by gas chromatography-high-resolution mass spectrometry

A method for the detection of clenbuterol in human scalp hair by gas chromatography-high-resolution mass spectrometry (GC-HRMS) is described. The sample preparation involved chemical digestion of the protein structure, which was achieved by incubating the hair with 1 M KOH at 70 degrees C. A single extraction step with tert.-butyl methyl ether provided approximately 90% of the analyte, which was dried and derivatized with N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA) to yield clenbuterol N,O-bis-trimethylsilyl (TMS). Hair was collected from four pregnant women who were therapeutically treated with Spiropent (clenbuterol-HCl) and from the infant of one female patient. Hair samples were taken during the application time and two to six months after completion of clenbuterol administration. The detection limit of the method was approximately 4 ng clenbuterol/g hair when 25 mg hair material were processed and 2 ng/g for 50 mg hair samples (corresponds to 4 pg per injection). The method allows clenbuterol to be measured retrospectively for up to at least six months. The levels of clenbuterol determined in hair ranged from 2 to 236 ng/g. No clenbuterol was found in the hair of the infant, which was taken five and a half months after delivery. To improve sample preparation, an additional purification step via immuno affinity chromatography (IAC) was integrated. The IAC purified extracts showed reduced biological background interference and an improved limit of detection (0.8 ng/g).

GC-MS determination of anabolic steroids after multi-immunoaffinity purification

For many years, EC regulations have prohibited the use of anabolic agents in food-producing animals. Multiple screening methods have been published, but some lack specificity and some are difficult to apply when screening for unknowns in surveillance programmes. This paper presents a new and powerful technique, combining multiresidue immunoaffinity chromatography and GC-MS, for the simultaneous identification and semi-quantification of various anabolic steroids in urine and faeces samples of bovine origin. It should reduce the cost, time and effort of screening by limiting the number of tedious clean-up steps and analyses required. A preliminary extraction step is applied to the individual biological specimens: solid-phase extraction followed by enzymatic digestion in the case of urine samples and a single liquid extraction step for faeces. This step is followed by a first clean-up step involving both a solid-phase column and a rapid RP-HPLC separation. The individual biological fractions (urine or faeces) are further purified on a multiresidue immunoaffinity chromatographic gel (MIAC-steroids-CER) so as to decrease interferences due mainly to background signals. A final trimethylsilyl derivatization is followed by the analysis of the biological samples by a sensitive and specific GC-MS procedure.

Comparison of purification procedures for the isolation and detection of anabolic residues in faeces using gas chromatography-mass spectrometry

Within several regional field laboratories and the national reference laboratory a harmonised methodology for the analysis of anabolic residues in faecal samples was developed. The method consists of a liquid-liquid and a solid-phase extraction step, followed by a high-performance liquid chromatography purification step. Using gas chromatography-mass spectrometry, currently illegally used anabolic steroids can be detected in faeces at the ppb level. Within this context acidification, followed by centrifugation under cooling, allows efficient, practical and rapid defatting of faecal samples. Furthermore, a combination of a silica and an aminopropyl solid-phase extraction column was found to give the best results as regards the sample purification process.

Multi-laboratory study of the analysis and kinetics of stanozolol and its metabolites in treated calves

The European Union banned the use of anabolic steroids for cattle fattening in 1988. Analytical techniques able to detect trace amounts of the parent drugs and their metabolites are mandatory for the control of abuse. Stanozolol (Stan) is an anabolic steroid that is often found in injection sites and cocktails. However, it has never been detected in tissues (kidney fat, meat) or excreta (urine, faeces) taken during regulatory inspection. The difference between the structure of Stan and the other steroids (a pyrazole ring fused to the androstane ring system) is probably the cause of this phenomenon. In the multi-laboratory study described here, veal calves were treated with intramuscular doses of Stan. In the excreta of these calves the presence, absence and/or concentration of Stan and of its major metabolites 16 beta-hydroxystanozolol and 3'-hydroxystanozolol were determined. For the determination of these analytes the different laboratories used different extraction and clean-up procedures and also evaluated different analytical techniques such as GC-MS (negative chemical ionization) and LC-MS-MS. The aim of this investigation was to explore which analyte should be validated for veterinary inspection purposes.

Quantitative determination of several synthetic corticosteroids by gas chromatography-mass spectrometry after purification by immunoaffinity chromatography

A study was conducted to test a multiresidue analytical procedure for detecting and quantifying several corticosteroids on which the European Union imposes maximum residue limits (MRLs). Primary extracts from different matrices (liver, milk, urine, faeces) were first purified on C18 cartridges. A new immunoaffinity clean-up step was included. The immunoaffinity gel was used to purify several corticosteroids simultaneously with enrichment of the corresponding fractions. The extracts were treated with an aqueous solution of pyridinium chlorochromate to fully oxidise all corticosteroids and to facilitate their extraction with dichloromethane. After evaporation, the final extract was reconstituted with toluene before injection into the GC-MS apparatus. The analysis was performed in the CI-negative ionisation mode using ammonia as the reactant gas. The estimated detection and quantification limits were, respectively, 0.25 and 0.5 ppb or lower. Overall, the method is reproducible to within 20%. Recovery is between 50 and 80% according to the corticosteroid.

Long-term detection and identification of metandienone and stanozolol abuse in athletes by gas chromatography-high-resolution mass spectrometry

The misuse of anabolic androgenic steroids (AAS) in human sports is controlled by gas chromatography-mass spectrometric analysis of urine specimens obtained from athletes. The analysis is improved with modern high-resolution mass spectrometry (HRMS). The detection and identification of metabolites of stanozolol (I) [3'-hydroxystanozolol (II) and 4 beta-hydroxystanozolol (III)] and metandienone (IV) I17 beta-methyl-5 beta-androst-1-ene-3 alpha,17 alpha-diol (V) and 18-nor-17,17-dimethyl-5 beta-androsta-1,13-dien-3 alpha-ol (VI)] with GC-HRMS at 3000 resolution yielded a large increase in the number of positive specimens. A total of 116 anabolic steroid positives were found in this laboratory in 1995 via GC-MS and GC-HRMS screening of 6700 human urine specimens collected at national and international sporting events and at out-of-competition testing. Of the 116 positive cases, 41 were detected using conventional (quadrupole) GC-MS screening. The other 75 positives were identified via GC-HRMS screening. To confirm the HRMS screening result, the urine sample was reanalyzed using a specific sample workup procedure to selectively isolate the metabolites of the identified substance. II and III were selectively isolated via immunoaffinity chromatography (IAC) using an antibody which was prepared for methyltestosterone and shows high cross reactivity to II and III. V and VI were isolated using high-performance liquid chromatography (HPLC) fractionation.

By-products of steroid synthesis: a cause of interferences in thin-layer chromatography residue analysis

Since the late 1980s all of the laboratories involved in high-performance thin-layer chromatography (HPTLC) control of hormonal residues in kidney fat, have occasionally detect a green fluorescent spot with similar RF values and colour to those observed for methyltestosterone (MT). This spot (product) could lead to false positive results for MT and was thus named 'le faux méthyl' (the false methyl) by a french speaking colleague. All of the samples with a false methyl spot also contained a relatively high concentration of progesterone. Differentiation of this product from methyltestosterone can be performed in three ways: firstly, extra HPTLC on reversed-phased plates, secondly, extra purification of the extract with HPLC prior to HPTLC and thirdly, gas chromatography--mass spectrometry. This interference was identified as 20 beta-hydroxyprogesterone, a by-product of progesterone. The problem of the false methyl was not only linked with the TLC characteristics of MT but also to the progesterone used as standard. Some laboratories used an analytical-reagent grade standard and others used commercial progesterone powders as standards (e.g., obtained in crude form from pharmaceutical companies). The commercial-grade progesterones showed two spots in comparison with the analytical standard that showed just one spot. As the false methyl was observed not only in kidney fat and meat samples, but also in illegal hormone cocktails, it was concluded that we had detected a by-product of an illegally used 'natural progesterone'.

Control of the illegal administration of natural steroid hormones in the plasma of bulls and heifers

In the context of the control of the illegal administration of natural steroid hormones in cattle husbandry, an attempt was made to establish the decision levels for sex steroid hormones in the plasma of adult cattle, taking into account the effect of the treatment. Bulls and heifers were treated with two injections, at a two week interval, of an estradiol-testosterone cocktail. Steroid hormone and biochemical precursor concentrations were measured in plasma samples by using specific radioimmunoassays, before and after the treatment. When the treatment significantly (p < 0.05) modified a hormone concentration, a decision level was established for that hormone concentration. At each decision level, a score was assigned that represented the percentage of treated animals detected when the decision limit was applied. For heifers, 17 beta-estradiol and testosterone concentrations in plasma, which increased after the treatment, are the best criteria to use to detect treated animals, with decision limits of 20 pg ml-1 and 125 pg ml-1, respectively. In the instance of bulls, both testosterone and steroid biochemical precursor concentrations decreased in the plasma after the treatment. We proposed decision limits of 1500 pg ml-1 and 28 pg ml-1 for testosterone and androstenedione concentrations, respectively, the bulls displaying concentrations below these limits being positive. We observed that the repetition of the injection increased the score of the decision limit. The scores for testosterone are 70%, 14d after the first injection and 100% 14 d after the second injection, and for androstenedione, these scores are 60 and 100%, respectively.

Combined immunoextraction approach coupled to a chemiluminescence enzyme immunoassay for the determination of trace levels of salbutamol and clenbuterol in tissue samples

A monoclonal immunoglobulin G1 (IgG1) antisalbutamol, which exhibits a 75% cross-reactivity with clenbuterol, has been used in the setup of an immunoaffinity chromatography method and a chemiluminescence enzyme immunoassay for the extraction and the quantification of salbutamol and clenbuterol in tissue samples. After analytical validation, the proposed methodology was applied to liver, kidney and muscle samples obtained from calves and pigs treated with these beta 2-agonists (100 micrograms per kg of body weight) for 10 d. This methodology allowed the quantification of both drugs until 6 d after the final dose. At this time, however, salbutamol and clenbuterol were concentrated in the liver. Our results indicate that the liver is the preferred tissue to sample for the detection of illegal use of beta 2-agonists as growth promoters, in the absence of urine samples.

Detection of clenbuterol residues in hair

Sixty rats were grown in the presence of 10 (n = 30) and 100 (n = 30) micrograms kg-1 body mass of clenbuterol for a period of 10 d. An immunoextraction step coupled with a competitive enzyme immunoassay allowed the quantification of clenbuterol in hair upon 20 (10 micrograms kg-1) and 30 d (10 micrograms kg-1) after the last dose. This accumulation in hair contrasts with the rapid clearance in tissues. The nature of the immunoreactive material was confirmed by mass spectrometry.

Radioimmunoassay of a bovine pregnancy-associated glycoprotein in serum: its application for pregnancy diagnosis

A sensitive and specific double-antibody RIA for a bovine pregnancy-associated glycoprotein (bPAG) is described. The limit of detection was 0.2 ng/ml. The assay was specific for bPAG in that pituitary and placental gonadotropic hormones and other placental or serum proteins assayed in serial dilutions did not cross-react. The RIA allowed measurement of bPAG in placental extracts, fetal serum, fetal fluids, and serum or plasma of pregnant cows. About 20% of unbred heifers and nonpregnant cows had detectable levels ranging from 0.30 +/- 0.09 to 0.50 +/- 0.17 ng/ml (mean +/- SD), and 15% of bull sera showed higher concentrations (3.01 +/- 1.73 ng/ml) of bPAG or bPAG-like protein. Variations among animals was observed in fetal serum bPAG concentrations. Bovine PAG was detected in maternal peripheral blood at Day 22 of pregnancy (mean +/- SD, 0.38 +/- 0.13 ng/ml) in some animals and at Day 30 in all pregnant cows. Peripheral serum bPAG levels increased progressively to 3.60 +/- 1.73 ng/ml (mean +/- SD) at Day 30 of pregnancy, to 24.53 +/- 8.81 ng/ml at Day 120, and to 1551.91 +/- 589.68 ng/ml at Day 270. Peak concentration of bPAG was 2462.42 +/- 1017.88 ng/ml and it occurred 1-5 days prior to parturition. After delivery, bPAG concentrations decreased steadily to 499.63 +/- 267.20 ng/ml at Day 14 postpartum (pp), 10.12 +/- 7.84 ng/ml at Day 60 pp, and 1.44 +/- 1.08 ng/ml at Day 90 pp. The undetectable concentration (less than 0.20 ng/ml) was reached by Day 100 +/- 20 pp. An investigation undertaken in Holstein heifers, Holstein cows, and Hereford cows used as recipients for purebred Holstein embryos supplied evidence of the influence of breed of recipient and sex of fetuses on peripheral concentrations of bPAG. A herd of 430 Holstein-Friesian heifers that had received transferred embryos were bled at Day 35 postestrus (pe) for measurement of bPAG. The bPAG was detected in 287 of 430 serum samples analyzed. By rectal palpation performed at Day 45 pe, 267 heifers with detectable levels of bPAG at Day 35 pe were confirmed to be pregnant as were 3 of 143 heifers previously diagnosed as not pregnant by RIA. These results suggest that detection of this placental-specific antigen in the serum could be used as a specific serological method for early pregnancy diagnosis in cattle from 28 days after breeding.

Identification and characterization of 19-nortestosterone in urine of meat-producing animals

To monitor the illegal use of 19-nortestosterone as an anabolizing agent in meat-production, the Belgian Institute of Veterinary Expertise applies a strategy of urine control by radioimmunoassay, positive samples being confirmed by thin-layer chromatography. We have evaluated this control strategy, using gas chromatography-mass spectrometry to confirm the presence of 19-nortestosterone, or its metabolite oestrane-diol, in positive samples from radioimmunoassay. Our results show that the effective way of proceeding remains reliable in cattle, for mature and immature males as well as non-pregnant females, and in pigs, for pregnant and non-pregnant sows. The possible presence of endogenous 19-nortestosterone in cattle, in pregnant cows urine, and in pigs, in boars and in cryptorchid pigs, impedes the control of the use of 19-nortestosterone on these samples. False-positive (not confirmed by gas chromatography-mass spectrometry) results were produced by radioimmunoassay in the urine of castrated pigs and sheep.

Development of a specific radioimmunoassay for the detection of clenbuterol residues in treated cattle

A radioimmunoassay for clenbuterol detection in cattle has been validated and used to monitor treated cattle. The tracer used was 4-amino-3,5-dichloro-alpha(tert-butylamino-methyl) benzyl alcohol (benzyl-3H)(clenbuterol) prepared by catalytic tritiation with tritium gas of 4-amino-3,5-dibromo-alpha-(tert-butylamino)-acetophenone, followed by chlorination at positions 3 and 5 in the aromatic ring. The rabbit antiserum was raised against a diazotized clenbuterol/human serum albumin conjugate. The assay described was sensitive (7.8 pg/tube) and reproducible. The intra- and inter-assay variability, which was assessed by measuring known quantities of clenbuterol in plasma, urine and faeces, was satisfactory for RIA. When this assay was used to monitor treated cattle the concentrations of clenbuterol in plasma, urine and faeces were directly related to the administered dose. The absorption and elimination of clenbuterol in cattle was rapid. Data obtained were consistent with results obtained in other species where a rapid clearance rate was also demonstrated.

Detection of cell proliferation in pig testis and intestine sections using monoclonal anti-bromodeoxyuridine antibody and immunogold silver staining

For the first time a monoclonal antibody against 5-bromodeoxyuridine was used to detect cell proliferation in pig testis and intestine sections. The influence of several parameters such as mode of injection, addition of thymidine biosynthesis inhibitor, tissue fixation, hydrolysis and revelation was examined. The technique of choice consisted in intravenously injecting the animals with 50 mg/kg BUdR added to 10 mg/kg FUdR 2 h before tissue collection and Bouin fixation; hydrolysis of sections was performed by HC1 4N: Ethanol 70 degrees (1:1 v/v); revelation of BUdR was made by a secondary antibody linked to colloidal gold particles, followed by a silver enhancement step. The data were superior when compared to those obtained by direct immunofluorescence and by the PAP technique. The described method is convenient and sensitive, provides an intense nuclear labelling without background and allows simultaneous examination of histology. The advantages over the technique using tritiated thymidine are particularly obvious when fast screening of numerous samples is required or when new experimental protocols are developing.