Development and validation of a procedure for determination of sulfonamide residues in pasteurized milk using...

An LC method for determination of 10 sulfonamides in milk using a modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method was developed. Unlike the standard QuEChERS method, addition of primary secondary amine was not required for the cleanup step. Sulfonamides were analyzed from the acetonitrile layer using LC/MS/MS with electrospray ionization. Sulfonamides studied included sulfanilamide, sulfadiazine, sulfathiazole, sulfamerazine, sulfamethiazole, sulfamethazine, sulfamethoxypyridazine, sulfamethoxazole, sulfadoxin, and sulfamethoxine. Three types of milk matrixes, namely, low- and high-fat liquid pasteurized milk and milk powder, were used in the study. Matrix effects of all three matrixes were studied. The LOQs for the 10 analytes for high-fat milk were 5.3-11.2 microg/L. The combined LOQ of the 10 sulfonamides was 83.15 microg/L, which is below the maximum residue limit recommended by the European Union for sulfonamides in milk.