An approach is described to validate a fast and simple targeted screening method for antibiotic analysis in meat and aquaculture products by LC-MS/MS. The strategy of validation was applied for a panel of 75 antibiotics belonging to different families, i.e., penicillins, cephalosporins, sulfonamides, macrolides, quinolones and phenicols. The samples were extracted once with acetonitrile, concentrated by evaporation and injected into the LC-MS/MS system. The approach chosen for the validation was based on the Community Reference Laboratory (CRL) guidelines for the validation of screening qualitative methods. The aim of the validation was to prove sufficient sensitivity of the method to detect all the targeted antibiotics at the level of interest, generally the maximum residue limit (MRL). A robustness study was also performed to test the influence of different factors. The validation showed that the method is valid to detect and identify 73 antibiotics of the 75 antibiotics studied in meat and aquaculture products at the validation levels.
Aquaculture has been the fastest growing animal production industry for the past four decades, and almost half of the fish eaten in the world are now farmed fish. To prevent diseases in this more intensive aquaculture farming, use of therapeutic chemicals has become a basic choice. The monitoring of malachite green, a triphenylmethane dye and one of the oldest and widely used chemicals in fish production, has gained more interest since the mid 1990s when this substance was finally proven to be toxic enough to be prohibited in seafood products destined for human consumption. The enforcement of the European Union (EU) regulation of this banned substance along with some other triphenylmethane dye congeners and their metabolites in its domestic production and in seafood imports was undertaken through the National Residue Monitoring Plans implemented in nearly all of the 28 EU member states. The reliability of the overall European monitoring of this dye contamination in aquaculture products was assessed by using the results of proficiency testing (PT) studies provided by the EU Reference Laboratory (EU-RL) in charge of the network of the EU National Reference Laboratories (NRLs). The proficiency of each NRL providing analytical support services for regulating dye residues was carefully checked during three PT rounds. In the process, the analytical methods developed and validated for this purpose have gradually been improved and extended over the last two decades.
Antimicrobial cross-contamination
of animal feed may occur during
feed manufacturing, because shared production lines can be used for
the production of medicated and nonmedicated feeds, and also during
feed transport, storage at the farm level, and usage. This is a major
issue in the current context in which antimicrobial usage must be
controlled to maintain their effectiveness. The purpose of this study
was to assess the antimicrobial cross-contamination rate of feed at
the farm level. Here, we optimized a liquid chromatography–tandem
mass spectrometry method for the determination of 11 antimicrobials
in feed for pigs, poultry, and rabbits, which were strategically chosen.
The method was validated according to European regulations in terms
of mass spectrometry identification criteria and quantification criteria
(linearity, trueness, precision, limit of quantification, and limit
of decision). The results were in compliance with these regulations
except for doxycycline, which may be quantified with higher uncertainty.
This method was applied to the analysis of 192 nonmedicated pig, poultry,
and rabbit feed samples that were collected directly from farms to
assess antimicrobials animal exposure. Cross-contamination rates were
relatively high with 44% of the samples being contaminated at a concentration
above the quantification limit of 0.125 mg/kg and 15% of the samples
being contaminated above 1 mg/kg. This result suggests that the current
regulations and feed processing recommendations need to be improved,
taking into account the risks arising from these contaminations.
Two interlaboratory studies were organized in 2002-2003 in order to check the proficiency of laboratories in confirming the presence of sulfonamide residues in muscle and milk. These studies involved 25 EU National Reference Laboratories (NRLs) from 21 different European Countries in charge of statutory monitoring of antimicrobial residues in food of animal origin at a national level. The study was conducted according to international and national guidelines by the Community Reference Laboratory (CRL) in charge of antimicrobial substances. Four different test matrices of sheep muscle and four different test matrices of bovine milk containing different sulfonamide substances were prepared and sent to the participants. Each participant was asked to use his own routine confirmatory method and to analyse each sample in triplicate within a period of about six weeks during which the stability of the materials was checked by the organizer. The sulfonamide content of each material was determined by calculating the robust means of all the results and the deviation of the results from the assigned values was assessed by calculating Z-scores. Overall, results were satisfactory, particularly considering that it was the first proficiency test dealing with sulfonamides organised by the Community Reference Laboratory.
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