Proficiency test for antibiotics in beef

The aim of this proficiency study was to give laboratories the possibility to evaluate or demonstrate their competence for the analysis of antibiotics in bovine tissues, including the screening analysis. This study also provided an evaluation of the methods applied for screening and quantitative and confirmatory analysis of antibiotics in beef

Proficiency test for antibiotics in bovine muscle

The aim of this proficiency study was to give laboratories the possibility to evaluate or demonstrate their competence for the analysis of antibiotics in bovine muscle, including the screening analysis. This study also provided an evaluation of the methods applied for screening and quantitative confirmatory analysis of antibiotics in bovine muscle

Homogeniteit als uitgangspunt voor monsternamestrategie : monsternamestrategie van partijen diervoedergrondstoffen in relatie tot de heterogeniteit voor controle op mycotoxines en dioxinen

In dit rapport wordt de monsternameproblematiek toegespitst op de analyse van mycotoxines en dioxinen in diervoedergrondstoffen. Eerst wordt in hoofdstuk 2 de Europese regelgeving betreffende monstername van diervoeders uiteengezet. In hoofdstuk 3 wordt de homogeniteit gedefinieerd en in hoofdstuk 4 wordt ingegaan op de onzekerheid in het eindresultaat. In hoofdstuk 5 worden relevante parameters voor beperking van de monsternameonzekerheid geïdentificeerd en worden methodes ter bepaling van de monsternameonzekerheid bediscussieerd. Op basis hiervan worden in hoofdstuk 6 conclusies getrokken en aanbevelingen gedaan voor vervolgonderzoek en een praktisch toepasbare strategie voor de controle van diervoedergrondstoffen op mycotoxines en dioxinen die moet leiden tot een betere interpretatie van analyseresultaten

LC-MS residue analysis of antibiotics : what selectivity is adequate?

In residue analysis of antibiotics quantitative and qualitative aspects are involved in declaring a sample non-compliant. The quantitative aspect regards the determination of the amount of the compound present in the sample. Validation procedures are available to determine the uncertainty of this result, which is taken into account in the decision making process. The qualitative aspect regards the confirmation of the identity of the compound present. In this, selectivity is the main parameter which is defined as the ability of a method to discriminate the analyte being measured from other substances. A trend observed in residue analysis is towards more generic methods for the detection of a broad range of compounds in a single run. As a result, by definition, selectivity is compromised. Procedures to determine the uncertainty of the qualitative aspect are lacking and, as a result, whether or not a method is adequately selective is a matter of experts’ judgment. In this thesis a method is presented for grading selectivity of methods using liquid chromatography coupled to tandem mass spectrometry. Based on the outcome it can be stated if selectivity is adequate and thus if a confirmatory result stands strong when challenged in a court case. If selectivity is found inadequate, additional measures can be taken like the selection of another product ion or the use of a third product ion to obtain adequate selectivity. Furthermore, two examples of analyses are presented in which selectivity plays an important role. First, the analysis of the banned antibiotic chloramphenicol (CAP). CAP contains two chiral centers and the nitro-group can either be para- or meta-substituted. Therefore, eight different isomers of CAP occur of which only RR-p-CAP is antimicrobially active. In the analysis of CAP, extreme selectivity is needed to distinguish the antimicrobially active compound from its inactive isomers. A method applying chiral liquid chromatography with tandem mass spectrometry was developed to discriminate antimicrobially active CAP for its inactive isomers. Also the research for the possible natural occurrence of this drug is presented. It is shown that CAP can be produced in unamended soil by Streptomyces venezuelaein appreciable amounts and that crops can take up CAP from soils. Therefore, it is concluded that CAP can occur in crops and animal feed due to its natural production by soil bacteria. Second, the development of a multi-ß-lactam method is presented. In this method a derivatization is applied to be able to effectively detect off-label ceftiofur use. In this selectivity is intentionally compromised and no unequivocal confirmation can be carried out using this method. The developed method is applicable to a wide range of ß-lactam antibiotics including penicillins, cephalosporins and carbapenems and is the best method available today for effective monitoring of off-label ß-lactam usage in poultry breeding. </p

Inter-laboratory study for tetracyclines in poultry muscle

The aim of this inter-laboratory study was to give laboratories the possibility to evaluate or demonstrate their competence for the analysis of tetracyclines in poultry muscle. This study also provided an evaluation of the methods applied for quantitative and confirmatory analysis of tetracyclines