Rapid Screening and Determination of Residual Amounts of β-Lactam Antibiotics in Foods by Ultrahigh-Performance Liquid Chromatography-High-Resolution Quadrupole Time-of-Flight Mass Spectrometry

We developed procedures for the rapid screening and sensitive determination of residues of 19 beta-lactam antibiotics in matrices of various food products (meat, kidneys, liver, bacon, milk, eggs, honey) using ultrahigh-performance liquid chromatography-high-resolution quadrupole time-of-flight mass spectrometry. Acetonitrile was used to precipitate proteins and extract analytes; the extract was used for analysis without further purification. Identification was performed by exact masses and retention times of analyte ions and by assessing the ion isotope distribution (mSigma). Penicillins form positively charged protonated adducts with methanol, while cephalosporins form protonated ions or adducts with sodium. We estimated matrix effect in the analysis of various samples. The matrix effect is slightly different for milk, meat, liver, kidneys, eggs, and salted pork fat (RSD <= 7%) and significantly different for honey. The detected analytes were quantified both by the standard addition method and using matrix calibration (RSD <= 5%). The recovery of beta-lactam antibiotics from different matrices in two versions of sample preparation ranged from 75 to 110%; RSD <= 11% under the conditions of matrix calibration. The limits of detection were 0.05-5 ng/g; the analytical ranges were from 1-10 to 200 ng/g (R-2 >= 0.99); the duration of screening the samples was 15-20 min; the duration of the analysis of the samples was 20-30 min.