Comprehensive validation of a liquid chromatography-tandem mass spectrometry method for the confirmation of chloramphenicol in urine including stability of the glucuronide conjugate and efficiency of deconjugation.

This paper describes a method to reveal the illegal use of chloramphenicol (CAP) in animals intended for human consumption based on the detection of free CAP and chloramphenicol-glucuronide (CAP-glu) in urine. It details the different steps of the method, including hydrolysis of CAP-glu, extraction and cleanup with molecularly imprinted polymers and detection by LC-MS/MS, as well as the validation design. The efficiency of chloramphenicol release during the hydrolysis step and the stability of CAP-glu in urine samples stored at -20°C were also investigated. These verifications were important to ensure the method's suitability for checking CAP misuse in veterinary medicine. Validation results were fully compliant with the qualitative and quantitative criteria required by European regulations. Intraday relative standard deviations were all below 7.5%, while interday relative standard deviations were below 6.9%. Recoveries lay between 93.3 and 104.6%. Purification appears very effective since no matrix effect was demonstrated. CAP-glu was found to be stable for at least 3 months, and the mean recovery following deconjugation was assessed to be 79.4%. The decision limits (CCa) were all found to be lower than 0.1µg/kg.

The Monitoring of Triphenylmethane Dyes in Aquaculture Products Through the European Union Network of Official Control Laboratories.

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.

Stability study for 53 antibiotics in solution and in fortified biological matrixes by LC/MS/MS.

This study was performed in order to determine the stability of antibiotics belonging to eight families in solution or biological matrix. Knowledge of the stability of antibiotics has to be demonstrated during method development or validation. The stability of stock standard solutions of 53 antibiotics was assessed after determining the appropriate conditions of dissolution and storage. The stability of the same 53 antibiotics after addition to negative control cow milk or pork muscle tissue stored at -18 and -70 degrees C was also assessed. Our concern was to obtain information concerning the stability of antibiotic residues in fortified biological matrixes in order to make easier the implementation of a routine screening method for antibiotic residues within the framework of the French monitoring program. Antibiotic solutions and fortified samples were analyzed using an LC/MS/MS method previously validated for screening purposes and for which it was checked that all pertinent criteria to obtain interpretable stability results were fulfilled. The design for testing the stability of antibiotics in solutions and matrix samples is described, as well as the rules of decision that were observed. Term periods for the stability study ranged from 1 month to 1 year, depending on the class of compounds. The results presented in this article will be useful and time-saving for many reference and field laboratories because LC/MS/MS methods are more and more commonly used for screening purposes.