Development and validation (according to the 2002/657/EC regulation) of a method to quantify sulfonamides in porcine liver by fast partition at very low temperature and LC-MS/MS

A novel multi-residue method for the quantification of 15 sulfonamides in porcine liver is described. It involves the application of a liquid-liquid extraction with fast partition at very low temperature (LLE-FPVLT) procedure followed by HPLC-MS/MS (high performance liquid chromatography coupled to tandem mass spectrometry) analysis. By this innovative method, acetonitrile is added to a minced porcine liver sample and the resulting suspension centrifuged and immersed in a container with liquid nitrogen for 15 s. The acetonitrile phase, which remains liquid under these conditions, is isolated, evaporated to dryness, recomposed with formic acid 0.1% v/v, and injected into the liquid chromatograph. The whole analytical procedure was validated according to the European Commission Decision 2002/657/EC and acceptable values (except for sulfanilamide) were obtained for the following parameters: linearity (0.97 < R2 < 0.99), decision limit (107.70 µg kg-1 < CCα < 128.65 µg kg-1), detection capability (115.40 µg kg-1 < CCβ < 157.29 µg kg-1), limit of detection (5.58 µg kg-1 < LOD < 16.75 µg kg-1), limit of quantification (18.41 µg kg-1 < LOQ < 55.26 µg kg-1), accuracy (recovery rates), precision (repeatability, intermediate precision, and measurement uncertainty tests), selectivity, and robustness. Recoveries higher than 70%, at three concentration levels (0.5, 1.0 and 1.5 of the maximum residue limit, MRL), were attained for the majority of the sulfonamides. These very promising results point to the inclusion of the present methodology into the National Residue Control Plan scope of the Ministry of Agriculture, Livestock and Food Supply of Brazil.