The Challenge of Standard Stability in LC-MS Based Multi-Analyte Approaches for Veterinary Drugs

Abstract

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 ℃ (with and without exposure to sunlight), respectively.Long-term stability testing conditions of intermediate mixes were -20 ℃, 4 ℃, 23 ℃ (with and without exposure to sunlight), and control temperature at -80 ℃ while the testing period was 2, 4, 8, and 12 weeks,respectively. Results indicated that calibration standards should ideally be stored at 4 ℃ 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 ℃ 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 ℃, without the presence of acid. Other classes of veterinary drugs were less critical as considers long-term stability. Overall, storage conditions at -20 ℃were considered optimal for long-term storage of intermediate mixes of veterinary drug standards.

Keywords

• veterinary drugs
• long-term stability
• short-term stability
• isochronous measurement
• lc-ms/ms