Analysis of sulfonamide residues in bovine liver by liquid chromatography-tandem mass spectrometry without chemical extraction or clean-up procedures

A new procedure for direct extraction and analysis of sulfonamides residues in bovine liver was developed. Briefly, an amount of homogenized sample was mixed with sand and incubated in an ultrasonic bath to promote tissue disruption. After, samples are centrifuged in an empty cartridge with a fritted glass filter. The filtrate was diluted with acetonitrile to precipitate proteins and centrifuged again. The final supernatant was diluted with HPLC mobile phase (ammonium acetate 10 mM: methanol, 85:15) and analyzed with a LC-MS/MS system with electrospray ionization in positive mode. Six sulfonamides were studied, and the procedure showed good recoveries values for all analytes, except for sulfamethoxazole and sulfaquinoxaline. Sulfapirydine was used as internal standard. Consumption of organic solvents was restricted to 2 mL of acetonitrile per sample.