Development and validation of a rapid LC-MS/MS method for the confirmatory analysis of the bound residues of eight nitrofuran drugs in meat using microwave reaction.

A rapid analytical method was developed and validated for the analysis of eight bound nitrofurans in animal tissue, shortening laboratory turnaround times from 4 to 2 days. The majority of methodologies for nitrofuran analysis focus on the detection of only four drugs (nitrofurantoin, furazolidone, furaltadone and nitrofurazone), and is time-consuming given the 16-h overnight derivatisation step and a double liquid-liquid extraction. In this study, the narrow scope of analysis was addressed by including further four important nitrofuran drugs (nifursol, nitrofuroxazide, nifuraldezone and nitrovin). Full chromatographic separation was achieved for the metabolites of all eight nitrofurans, using phenyl-hexyl column chemistry and a rigorous optimisation of the mobile phase additives and gradient profile. The conventional, lengthy sample preparation was substantially shortened by replacing the traditional overnight water bath derivatisation with a rapid 2-h microwave-assisted reaction, followed by a modified-QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) extraction. This confirmatory method was fully validated in accordance with the new 2021/808/EC legislation, and was shown to perform satisfactorily when applied to incurred tissues. The decision limit (CCα) for the eight analytes ranged between 0.013 and 0.200 µg kg, showing abundant sensitivity given that the current RPA for nitrofurans is 0.5 µg kg. This innovative method can play a major role in the surveillance of the illegal use of nitrofuran drugs.