Determination of Colistin B in Chicken Muscle and Egg Using Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry.

Colistin, an imperative member of the polymyxin group, is a cationic peptide antibiotic. Itis also known as polymyxin E, but this peptide antibiotic has been forbidden for human consumption due to its high toxicity. Regrettably, this antibiotic is utilized as a feed additive and veterinary drug for animals. Due to the toxicity of colistin, the presence of its residue in the animal system represents a threat to human health regarding the consumption of meat, especially chicken. A novel method was proposed for quantifying colistin B in chicken muscles and eggs using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). In this method, extraction of colistin B from samples was achieved by mixing the sample with acidified methanol:water (1/1, v/v), followed by centrifugation and filtration by a membrane filter excluding solid-phase extraction (SPE) clean up, as well as evaporation steps. The analysis was conducted by optimized liquid chromatography-tandem mass spectrometry (LC-MS/MS), and method performance was assessed in terms of the limit of quantitation, specificity, selectivity, precision, linearity and recovery in coherence with the guidelines of SANTE and the Commission Decision 2002/657/EC. The result obtained from the study showed the limit of quantitation (LOQ) as 10 µg Kg-1 for muscles and 5 µg Kg-1 for eggs, with acceptable recoveries along with precision. The linearity was plotted in the range of 5-25 µg L-1 (solvent) for egg and 10-50 µg Kg-1 (matrix-matched) for muscles. The result of average recoveries showed the value of 70-94% (3.3-12% relative standard deviation (RSD)) for chicken muscles and 88-107% (2.5-18.6% RSD) for egg samples, which meets the criteria for acceptability of method according to both SANTE and 2002/657/EC guidelines. This proposed protocol provides a cost-effective solution for food testing labs by reducing the cost of the sample preparation by 60% along with the time required for SPE cleanup. Further, the optimized method was also tested on real samples collected from nearby provinces in Solan city, Himachal Pradesh, India, and three out of 20 muscles were found to have colistin B in the range of 50-560 µg Kg-1.