Determination of the stability of antibiotics in matrix and reference solutions using a straightforward procedure applying mass spectrometric detection

Abstract

The stability of an antibiotic is a very important characteristic, especially in the field of antibiotic residue analysis. During method development or validation, the stability of the antibiotic has to be demonstrated no matter if the method is used for screening, confirmation, qualitative or quantitative analysis. A procedure for testing the stability of antibiotics in solutions and food samples using LC-MS/MS is described. The procedure is based on the assumption that the antibiotics are stable when stored at -70 °C. Representative solutions or spiked samples containing the antibiotic were stored at the temperature to be tested (-18 or 4 °C) and at -70 °C. After a selected storing time samples were moved from the chosen storage temperature to -70 °C. At the end of the study, all samples--per class of antibiotic--were analysed in one batch. By applying statistical models, it was finally concluded in which circumstances the antibiotic is stable. The stability of 60 antibiotics belonging to the classes of tetracyclines, sulphonamides, quinolones, penicillins, macrolides and aminoglycosides were tested. The stability of solutions containing tetracyclines and penicillins is only guaranteed for 3 months while stored at -18 °C. Solutions of all other antibiotics tested are stable for at least 6 or 12 months when stored at 4 °C. In muscle tissue stored at -18 °C no severe degradation of the tested antibiotics was observed, with the exception of the penicillins. The stability data reported here are useful as a reference for laboratories carrying out validation studies of analytical methods for antibiotic (residue) detection. The data should save the time needed for long-term stability testing of solutions and samples.

Analysis of 76 veterinary pharmaceuticals from 13 classes including aminoglycosides in bovine muscle by hydrophilic interaction liquid chromatography–tandem mass spectrometry

“…Very limited degradation was observed for all tested analytes during a storage period of 60 days (2 months) at −18 • C. The recovery ratio after and before storage was between 0.90 and 1.05 for all the veterinary drugs and pharmaceuticals, except for ampicillin which was subjected to a degradation of approximately 12%. These results come into agreement with previous published studies [46,[48][49][50]. Therefore, it was concluded that tissue samples that are kept frozen before analysis must be analyzed within the first 8 weeks of sample receipt.…”

“…As it has been repeatedly reported in literature, these antibiotics show severe instability if stored for over than a 3-month period, even at −18 • C [2,46,47]. All other analytes present no degradation for at least 6 months when stored at −18 • C [2,[46][47][48][49][50]. Table S2.…”

Identification and Characterization of the First Cathelicidin from Sea Snakes with Potent Antimicrobial and Anti-inflammatory Activity and Special Mechanism

“…Many traditional antibiotics, including ␤-lactam antibiotics, cephalosporins, tetracyclines, and quinolones, are often unstable in aqueous solutions, which significantly restricts their usage (31,32). In contrast, Hc-CATH is extremely stable in aqueous solution (Fig.…”

Reconnaissance of 47 antibiotics and associated microbial risks in seafood sold in the United States

“…A previous study, examining the effect of sample storage at −18°C, showed that tetracyclines, sulfonamides, quinolones, macrolides, and aminoglycosides are stable and remain intact structurally and quantitatively, as demonstrated using a porcine muscle matrix [43]. However, penicillins were observed to attenuate, by about 30% and 20%, respectively, for ampicillin and cloxacillin over the course of 3-6 months [43]. Hence, the concentrations of penicillins at the time of purchase in samples of seafood analyzed here may have been higher than the values of less than <1.2 to <1.6 ng/g fw reported here.…”