How to improve analytical strategies to monitor growth promoting agents misuse in cattle

Transcription

1 5th interantional Symposium on Recent Advances in Food Analysis Prague, Czech Republic, 1-4 November 2011 How to improve analytical strategies to monitor growth promoting agents misuse in cattle Emmanuelle Bichon, Sandrine Rochereau, Ludivine Sérée, Stéphanie Prevost, Fabrice Monteau, Bruno Le Bizec LUNAM Université, Oniris, Laboratoire d'etude des Résidus et Contaminants dans les Aliments (LABERCA), Nantes, F-44307, France

2 1. Introduction According to the European Regulation, growth promoting agents are forbidden in animal breeding (Annexe I of the 96/23/EC decision). Nowadays, the well known xenobiotics, i.e. methyltestosterone or clenbuterol, are very well monitored by the EU laboratories in implementing specific sample preparations followed by liquid or gas chromatography coupled to tandem mass spectrometry. However, the analytical strategies have to be always up to dated to fight the novel forbidden practices. Actually, it seems probable that either new b-agonists or natural steroids can be used in the goal to be transparent to the analysis. Indeed, the analytical signals are respectively not monitored because the structure is unknown or masked by the natural occurrence in the matrix of interest. This presentation aims to synthesize the novel analytical strategies that can be used to monitor new β-agonists, estradiol and zeranol in animal breeding. Natural compounds Incurred sample 17a-testosterone bb Unknown compounds clenbuterol 17a-testosterone bb Untreated animal Unknown β-agonist 2/9

3 2. How to highlight of unknown compounds? β-agonists in feed Context β-agonists belongs to the group A5 in the annexe I of the 96/23/EC directive. Its use is forbidden in animal breeding in the EU. Cl H 2 N HO Cl HN H 3 C NH The well known β-agonists, like clenbuterol, zilpaterol, isoxuprine and ractopamine, are generally monitored in LC-(ESI+)-MS/MS in single reaction monitoring. However, a lot of new β-agonists can be synthetised around the same generic part called «phenylethanolamine». In order to also monitor such compounds, a specific analytical strategy is performed based on a MIP sample preparation followed by a LC-MS/MS analysis in the neutral loss acquisition mode. Actually, the loss of water, which is not generally specific, allows screening the whole β- agonist family. NH HO O N NH Neutral Loss relevance Fragmentation of Clenbuterol in ESI+ MS/MS at 15 ev Cl H 2 N Cl HN H 3 C [M+H] /9

4 2. How to highlight of unknown compounds? β-agonists in feed : protocol and results Protocol 5 g Feed 40 ppb deuterated internal standard Results Internal std 15 ml Me 20 ml COONa 0.2 M, ph 5.2 Spike Sample Shaking and Centrifugation Molecular Imprinted Polymer Reconstitute in 80:20 H 2 O/Me Discussion UPLC-MS/MS NL 18 ESI + The results shown on the right are illustrated with three different feed samples, whom on the top, a spike with a mixture of more than 15 β-agonists, on the middle a blank sample and on the bottom an unknown feed sample. In spite of the low specificity giving by the neutral loss of 18, the results demonstrate a efficient interpretation in using a specific MIP to prevent coeluted analytes. The blank sample is easy to interpretate and the conclusions are the same for unknown samples (in this case, a compliant sample). Blank Sample Unknown Sample 4/9

5 2. How to highlight natural compound abuse? Estradiol in cattle Context Estradiol belongs to the group A3 in the annexe I of the 96/23/EC directive. Its use is forbidden in animal breeding in the EU. Procedure 2 ml bovine plasma Enzymatic hydrolysis H LLE ether (1) HO H H copolymeric SPE (1) LLE Pentane (1) Si SPE (1) MIP: estradiol (AFFINIMIP Polyintell) In 1989, a threshold was set up at 40 pg.ml -1 in bovine plasma for animals below 2 years old above which the sample was conclude non compliant. To assure such a sensitivity, a purification based on MIP step was developed to simplify the powerful but more expansive method (1). Preparative HPLC (1) dimethylaminopropyle Derivatisation PFB/TMS (1) GC-MS/MS Derivatisation TMS (1) F. Courant et al. Analytica Chimica Acta 2007;586: /9

6 2. How to highlight natural compound abuse? Estradiol in cattle : performances Results The quantification is performed until 10 pg.ml -1 with two transitions detected per analyte. Blank plasma 10 ppt 40 ppt 100 ppt 17β-estradiol-d 3 419>285 17α/β-estradiol 416>129 17α/β-estradiol 416>285 The threshold at 40 pg.ml -1 can be now monitored with a rapid and efficient sample preparation and a classical ionisation in electronic impact with TMS derivatisation. 6/9

7 2. How to highlight natural compound abuse? Zeranol abuse in cattle Context Procedure Zeranol belongs to the group A4 in the annexe I of the 96/23/EC directive. Its use is forbidden in animal breeding in the EU. 2 ml bovine urine Enzymatic hydrolysis O O MIP Zearalenone IAC Zeranol HO NH 2 SPE This compound is also an urinary metabolite of the Fusarium sp. toxin called zearalenone. LC-(ESI-)-MS/MS MRM To confirm the administration of zeranol, the strategy is based on the Launay (1) approach, where the 6 main metabolites have to be quantified before to conclude to an administration. To improve the efficiency of the method, three strategies using two specific purifications were tested : - MIP zearalenone (Affinimip, Polyintell, France); -immunoaffinity column (IAC) Zeranol (CER, Belgium). The strategies are described on the right. Log (Zeranol+Taleranol) (ng/ml) Projection according to Launay et al. (2004) 1 2 1,5 1 0,5 0-0, ,5 Log Fusarium toxin (ng/ml) 1 Launay et al. Food Additives and Contaminants, Vol. 21, No. 9 (September 2004), pp /9

8 2. How to highlight natural compound abuse? Zeranol abuse in cattle Results If the MIP is used alone, the MIP cartridges remain not enough specific for zeranol and taleranol purification for urine purification at ppb levels (a). However, the addition of an NH 2 cartridge discards all the coeluted compounds and induces best quantification results (loss of matrix effect (b)). Nevertheless, recoveries on taleranol are two times lower than those for zeranol (c). With the immunoaffinity column (IAC) Zeranol, the specificity is excellent but recoveries are lower for zearalanone (d). Regarding the cost of each strategy, the prices between MIP+NH2 and IAC (if IAC is reused at least 10 fold) are equivalent. The MIP+NH 2 strategy is finally chosen for a confirmatory method. Spike urine (1 ng.ml -1 ) MIP+NH 2 MIP IAC Taleranol-d4/Zeranol-d4 Taleranol/Zeranol (c) (b) (a) α/β-zearalenol Zearalenone (d) Zearelenone 8/9

9 5. Conclusion The aim of the presentation was to propose several analytical tools dealing with in the same time the improvement of the sample preparation and an associated specific detection. These developments are led in keeping in mind the solvent consumption and the time of preparation and analysis. After general considerations, we have based our discussion on several examples, whom the animal feed preparation with MIP-β-agonists in order to analyze all the known and unknown compounds by LC-(ESI+)-MS/MS in neutral loss mode; the serum preparation on MIP to analyze estrogens residues by GC-MS/MS after TMS derivatisation at very low levels (down to ppt level) and the comparison of zeranol and Fusarium sp. metabolites analysis by LC-(ESI-)- MS/MS after different sample preparations, i.e. immunoaffinity, MIP or successive SPE. These strategies appeared very promising to prevent misuse of such new or natural compounds. During this last decade, the improvement of the analytical instruments but also the development of specific sample preparation supports like MIP have contributed to reach these kind of analytical performances to open new features for growth promoter monitoring. 9/9