Residue study of nitroimidazoles depletion in chicken feathers in comparison with some other selected matrixes.

This paper presents the results from a residue study conducted on a statistically representative number of chicken broilers that were individually orally treated with the selected nitroimidazoles (metronidazole, ornidazole and ipronidazole) in an appropriate amount close to the theoretical therapeutic dose. A mutual persistence comparison of the monitored analytes in feathers, serum, muscle and shanks was performed and attention was also paid to selected metabolites (hydroxymetronidazole and hydroxyipronidazole). An analytical LC/MS/MS method using SupelMIP SPE nitroimidazoles cartridges was developed for the determination of nitroimidazoles residues in poultry feathers, serum, muscle and shanks and the method was validated according to Commission Decision 2002/657/EC. High concentrations of nitroimidazoles residues in feathers were observed 19 days after the broilers' treatment unlike the muscle and serum samples, where nitroimidazoles depletion was significantly faster (residue concentrations were below detection limits in 5 days in muscle and in 12 days in serum). Shanks (chicken claws) also proved to be a very useful matrix for the detection of nitroimidazoles drugs misuse due to the longer persistence of these drugs residues and their metabolites in this matrix (determinable concentrations were observed 19 days after the broilers' last treatment). Feathers and shanks appear to be suitable matrixes for the screening of various nitroimidazoles in poultry because long-term persistence of residues enables reliable detection of the illegal use of nitroimidazoles compounds in official checks.

Method for the determination of thyreostats in milk samples using LC-MS/MS.

A sensitive and selective analytical method for the determination of four thyreostats (tapazol, thiouracil, methylthiouracil and propylthiouracil) in cow's milk, lamb's milk, and goat's milk was developed and validated according to 2002/657/EC criteria. Proteins in milk samples were precipitated by acetonitrile and analytes were derivatised with 3-iodobenzylbromide. Afterwards, derivatives were separated from the matrix by liquid-liquid extraction with ethyl acetate as an organic solvent and analysis was carried out using LC-MS/MS in a positive electrospray mode. The method provides, for all determined analytes, decision limits CCα below 1 ng ml(-1) and a detection capability CCß value below 1.5 ng ml(-1). The stability of analytes in sample extracts stored at various conditions was also tested and evaluated.