An analytical method was established for the determination of the residues of 11 sulfonamides and five quinolones in infant formula milk powder using ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS). Acidified acetonitrile was used for sample extraction and the extract was purified and concentrated by solid phase extraction (SPE) using a PRiME hydrophilic lipophilic balance (HLB) column, then separated on an XBridge BEH C18 column, detected in the positive ion mode using an electrospray ionization source, and quantified by the calibration curve method with matrix matching. The calibration curves of all analytes showed a good linear relationship in the concentration range of 2–100 ng/mL with correlation coefficients greater than 0.995 0. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1-0.2 and 0.3-0.5 μg/kg, respectively. Recoveries for spiked samples were between 84.8% and 108.0%, with relative standard deviations (RSDs) between 0.36% and 5.41%. The proposed method is simple, efficient, reliable and sensitive.

An ultra-high performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS) method was established for the determination of six quaternary ammonium disinfectant residues in milk-containing food for special medical purposes. The sample was extracted with 80% acetonitrile in water and the extract was separated on a RRHD Eclipse Plus C18 column, detected in the positive ion mode using an electrospray ionization source with multiple reaction monitoring (MRM), and quantified by matrix-matched standard calibration. The calibration curves for the six quaternary ammonium disinfectants was linear in the concentration range of 0.1–5.0 ng/mL with correlation coefficient higher than 0.996 0. The limit of detection (LOD) was 0.5 μg/kg and the limit of quantification (LOQ) was 1 μg/kg. The recoveries were 72.8%-102.3% for spiked solid matrix samples, and 71.8%–100.8% for spiked liquid matrix samples with relative standard deviations (RSDs) in the range of 0.25%–3.88% and 0.19%–2.51%, respectively. The proposed method is simple, efficient, rapid, sensitive, and suitable for the qualitative and quantitative analysis of quaternary ammonium disinfectant residues in food for special medical purposes.