Development and Validation of Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) Methods for the Analysis of Veterinary Drugs in Various Biological and Feed Matrices Utilizing Efficient Extraction Protocols
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1.4 CHEMICAL SCIENCES
The transfer of farming practices from low intensity farming systems for livestock production to commercial enterprises which employ intensive practices has resulted in the use of veterinary drugs becoming a critical component of food production. Resulting residues of veterinary drugs occurring in food of animal origin may give rise to potential health risks to consumers. The aim of this research is the development of analytical methods capable of screening and confirming increased number of these residues in more target matrices by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS). Its focus is the analysis of nitroimidazole residues in food of animal origin and authorised and prohibited medicinal additives in animal feed. This research resulted in the development and validation of methods for analysis of nitroimidazoles (NMZs) in plasma, eggs, milk and honey and prohibited and authorised medicinal additives in animal feed. The analytical technique used in all methods was the highly selective and sensitive LC-MS/MS. This technique allowed for multi-analyte methods to be developed for different matrices. NMZ residues examined were metronidazole, dimetridazole, ronidazole, ipronidazole, ternidazole, ornidazole, carnidazole and tinidazole along with three metabolite, hydroxymetronidazole, 2-Hydroxymethyl-1-methyl-5-nitroimidazole (HMMNI) and hydroxy-ipronidazole. Chloramphenicol was included with the analysis of NMZs in the matrices of milk and honey. Fourteen medicinal additives; metronidazole, dimetridazole, ronidazole, ipronidazole, clopidol, carbadox, sulfadiazine, sulfamethazine, dinitolimide, chloramphenicol, ethopabate, avilamycin, tylosin and virginiamycin were analysed for in animal feed. The final method developed allowed for coccidiostats; halofuginone, robenidine, nicarbazin, diclazuril, decoquinate, iii semduramicin, lasalocid, salinomycin, monensin, narasin and maduramicin to be analysed for at levels related to unavoidable carryover in feed. All veterinary residue methods used were validated in accordance with EU legislation; Commission Decision 2002/657/EC. This legislation is concerned with the performance of analytical methods and the interpretation of results. Validation criteria were examined using protocols set out in this legislation and these included specificity, accuracy, precision, repeatability, reproducibility, decision limits (CCα), detection capabilities (CCβ) along with measurement uncertainty (MU). In the four methods developed for the analysis of NMZ residues in plasma, egg, milk and honey the accuracy and precision for all analytes ranged from 87.2% to 108.9% and 3.7% to 11.3% respectively in all matrices. CCα and CCβ for all nitroimidazole residues ranged from 0.33 to 1.60 g L-1 / g kg-1 and 0.56 to 2.64 g L-1 / g kg-1 respectively with MUs ranging from 18 to 90% for all compounds in the various matrices. Chloramphenicol CCα and CCβ values were below its minimum required performance level (MRPL) of 0.3 g L-1 / g kg-1. At present there is no legislation in place describing validation approaches for methods used for the analysis of medicinal additives in animal feed. Therefore for the validation of the two feed methods developed as part of this research the veterinary residue legislation was used as a basis. In the case of the analysis of coccidiostats at unavoidable carry over levels; the method was validated entirely in accordance with veterinary residue legislation, Commission Decision 2002/657/EC. However the method for the analysis of 14 prohibited medicinal additives in feed was validated with some adaptations to this legislation. To ensure that the method was fit for purpose a wide variety of feed was used in validation and a wider concentration range was examined. Parameters of specificity, accuracy, precision, iv repeatability, reproducibility were all examined and deemed to be acceptable along with measurement uncertainty.
Cronly, M.: Development and Validation of Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) Methods for the Analysis of Veterinary Drugs in Various Biological and Feed Matrices Utilizing Efficient Extraction Protocols. Doctoral Thesis. Dublin Institute of Technology, 2011.