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The short- and long-term stability of multi-component mixtures and intermediate mixtures of analytical standards of veterinary drugs, which can potentially occur in food and feed chains, was examined by an isochronous measurement approach. Short-term stability testing of calibrants included storage for 1, 2, 4, and 7 days at --20 (as a baseline) 4, and 23 °C (with and without exposure to sunlight), respectively. Long-term stability testing conditions of intermediate mixes were --20 °, 4 °C, 23 °C (with and without exposure to sunlight), and control temperature at --80 °C while the testing period was 2, 4, 8, and 12 weeks, respectively. Results indicated that calibration standards should ideally be stored at 4 °C for only 1-2 days, without the presence of acid. Neutral storage conditions were acceptable even at room temperature. Storage of intermediate mixtures containing ß-lactams and cephalosporins for longer than 1 month under 4 °C and room temperature resulted in a loss of almost 90%. When it comes to the intermediate mixtures with penicillin V and G, acceptable storage conditions were 2 weeks at --20 °C, without the presence of acid. Other classes of veterinary drugs were less critical as considers long-term stability. Overall, storage conditions at --20 °C were considered optimal for long-term storage of intermediate mixes of veterinary drug standards. [ABSTRACT FROM AUTHOR]