UHPLC-MS/MS Determination of Residual Amounts of 16 Benzimidazoles in Milk Powder

The sample (2.000 0 g) was extracted ultrasonically for 5 min with 8 mL of 0.1 mol·L^-1 hydrochloric acid solution and 7 mL of acetonitrile. The extract was purified on activated MCX solid phase extraction (SPE) column. The purified solution after treatment was separated by UHPLC using Waters ACQUITY UPLC BEH column as the stationary phase, and mixtures of 0.02% (φ) formic acid solution and acetonitrile, mixed in various volumic ratios, as mobile phase in gradient elution. ESI⁺ and MRM were adopted in MS. Linear relationships between values of peak area and mass fraction of 16 benzimidazoles were found in definite ranges, with detection limits (3S/N) in the range of 3.2-4.4 μg·kg^-1. Test for recovery was made by standard addition at 3 concentration levels, giving results in the range of 82.0%-108%, with RSDs (n=6) all less than 9.0%.