Liquid chromatography-tandem mass spectrometry method for the determination of dye residues in aquaculture products: development and validation.

A method is described for the identification and the quantitative determination of the triphenylmethane dyes, malachite green (MG), crystal violet (CV), brilliant green (BG) and leuco malachite green (LMG) and leuco crystal violet (LCV). The analytes were isolated from the matrix by liquid-liquid extraction with acetonitrile. Determination was performed using LC-MS/MS with positive electrospray ionisation. 4 different deuterated internal standards were introduced to improve the quantitative performance of the method. The method has been validated in line with the EU criteria of Commission Decision 2002/657/EC in accordance with the minimum required performance limit (MRPL) set at 2 µgkg(-1) for the sum of MG and LMG. For all the monitored compounds, accuracy, intra-day and inter-day precision were determined at each level of fortification (0.5, 0.75, 1.0 and 2.0 µgkg(-1)). Decision limits CCα and detection capabilities CCß were calculated according to the standard ISO 11843-2. A study on the applicability of the method was conducted on various aquacultured species with the aim to assess the matrix effects. The presence of residues of leuco brilliant green in fish has also been confirmed from experimental study performed on trout treated with brilliant green, using LTQ-Orbitrap mass spectrometer.

Stability of penicillin antibiotic residues in meat during storage. Ampicillin.

Incurred samples from a pig treated with ampicillin, one of the most important penicillin antibiotic drugs used in food-producing animal treatments, were analyzed at the residue level of the drug in muscle tissue (approximately 100 microg kg(-1)) during their freezing storage and using three different techniques: quantitative microbiological assay, HPLC-UV and LC-MS. Two parameters have been specifically monitored: storage temperature (-20 and -75 degrees C) and storage packaging (ground meat or bulk meat). No significant decrease was observed during the first 3 months of storage monitoring at -20 and -75 degrees C. On the contrary, the sample preparation significantly affected the drug concentration in muscle from the very beginning of the storage. Grinding the meat before storage allowed to keep the drug near the higher level of concentration (approximately 100 microg kg(-1)) when bulk meat stored frozen systematically led to a decreased value (approximately 75 microg kg(-1)). After 8 months of storage at -20 degrees C, a significant decrease arose and was never observed at -75 degrees C. All the results were similarly obtained with the three different techniques used simultaneously, which allows to indicate a good correlation between the techniques.

Multiresidue analytical method for the determination of eight penicillin antibiotics in muscle tissue by ion-pair reversed-phase HPLC after precolumn derivatization.

A high-performance liquid chromatographic multiresidue method was developed for the determination of 8 penicillin compounds (benzylpenicillin, phenoxymethylpenicillin, ampicillin, amoxicillin, nafcillin, oxacillin, cloxacillin, and dicloxacillin) at trace levels in muscle tissue. This method involves extraction of the penicillins with phosphate buffer pH 9 followed by cleanup and concentration on a C18 solid-phase extraction column and reaction with benzoic anhydride at 50 degrees C for 5 min and with 1,2,4-triazole and mercury(II) chloride solution pH 9 at 65 degrees C for 10 min. The derivatized compounds are eluted on a C8 column with a mobile phase containing acetonitrile and phosphate buffer (pH 6; 0.1 mol/L) loaded with sodium thiosulfate and ion-pairing tetrabutylammonium hydrogenosulphate. The method detection limit is approximately 3-11 micrograms/kg and the limit of determination was evaluated down to 25 micrograms/kg in line with the criteria of the EU decision No. 93/256/EEC.

Determination of isoxazolylpenicillins residues in milk by ion-pair reversed-phase high-performance liquid chromatography after precolumn derivatization.

A high-performance liquid chromatographic method has been developed for the determination of isoxazolylpenicillins (oxacillin, cloxacillin and dicloxacillin) residues in milk. This method involves extraction of the penicillins from milk with phosphate buffer pH 8, deproteinization by acidification with sulfuric acid followed by cleanup and concentration on a C18 solid-phase extraction column and reaction with 1,2,4-triazole and mercury(II) chloride solution pH 9.0 at 65 degrees C. The derivatized compound is eluted on a C8 column with a mobile phase containing acetonitrile, methanol and phosphate buffer (pH 6.5, 0.1 mol l(-1)) loaded with sodium thiosulfate and ion-pairing tetrabutylammonium hydrogenosulphate. The detection limit of the method is 2 microg l(-1) for oxacillin, 3 microg l(-1) for cloxacillin and 5 microg l(-1) for dicloxacillin in milk and the three penicillins have been quantified down to 15 microg l(-1) in line with the EU criteria of the directive No. 93/256/EEC.

Determination of ampicillin residues in milk by ion-pair reversed phase high performance liquid chromatography after precolumn derivatization.

A high performance liquid chromatography method has been developed for the determination of ampicillin residues in milk. The method involves extraction of ampicillin from milk with trichloroacetic acid solution followed by concentration on a conditioned C18 solid phase extraction column, acetylation with acetic anhydride in aqueous solution (pH 8.0) at ambient temperature for 3 min followed by reaction with 2 M 1, 2, 4-triazole and 10(-2) M mercury (II) chloride solution (pH 9.0) at 65 degrees C for 10 min. The resulting product is eluted on a C18 column with a mobile phase containing phosphate buffer (pH 6.5; 0.1 M), the ion-pairing agent tetrabutylammonium hydrogenosulphate, acetonitrile and methanol. The detection limit of the method is 3 ng ml-1 in milk.