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Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2018 Apr;35(4):695-705. doi: 10.1080/19440049.2018.1433333. Epub 2018 Feb 20.

Stability study of veterinary drugs in standard solutions for LC-MS/MS screening in food.

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a Nestlé Research Center , Institute of Food Safety and Analytical Science , Lausanne , Switzerland.
b LGC Labor GmbH , Analytical Service , Augsburg , Germany.


A study on stability of veterinary drugs in standard solutions stored at -80°C and at -20°C was conducted over 1 year. Data were acquired on 152 individual stock standard solutions and also on 15 family mixes and 2 working standard solutions. All solutions were prepared, stored and compared 1 year later against freshly prepared ones by LC-MS/MS. A statistical analysis was performed to set the acceptability criteria, taking into account the variability of standard preparations. In individual stock standard solutions stored at -80°C (12 months) and -20°C (9 months), stability was demonstrated for 141 and 140 out of 152 compounds, i.e. for 92% and 93% of compounds, respectively. Drugs were even more stable when solubilised in either diluted family mixes or working standard solutions, with more than 99% and 94% of compounds found unaltered when stored at -80°C and at -20°C, respectively. In mixes, beta-lactams from the cephalosporin (cefadroxil and cephalexin) and penicillin (amoxicillin and ampicillin) families were found to be the least stable compounds when stored at -20°C (6 months), necessitating storage at -80°C to achieve a 1-year shelf life. The study also evidenced solubility issues for two sulfonamides (sulfadiazine and sulfamerazine) in methanol-based solutions. An independent stability study conducted by a second laboratory confirmed the 1-year stability of 3 family mixes-quinolones, sulfonamides and tetracyclines.


LC-MS/MS; Veterinary drugs; stability study; standard solutions

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