An ultra-high performance liquid chromatography (UPLC) method was developed for the simultaneous determination of 19 free amino acids and taurine in formulas for special medical purpose intended for infants. The samples were hydrolyzed by α-amylase, and purified by precipitating proteins and other impurities through pH adjustment. The method was based on pre-column derivatization with 6-aminoquinolinyl-N-hydroxysuccinimidate (AQC). Formic acid-ammonium formate (20 mmol/L, pH 2.25), formic acid-ammonium formate (20 mmol/L, pH 3.00), and acetonitrile were used as mobile phases A, B and C for gradient elution, respectively. The analytes were separated on an AccQ-Tag Ultra C₁₈ column, detected with a diode-array detector and quantified by an external standard method. Good linearity was observed for cystine in the range of 5–125 μmol/L and 18 other amino acids and taurine in the range of 10–250 μmol/L with correlation coefficients higher than 0.999. The limit of detection (LOD) was 1.5 μmol/L for cystine, and 3 μmol/L for the other analytes. The limit of quantitation (LOQ) was 5 μmol/L for cystine, and 10 μmol/L for the other analytes. The average recoveries of the method were in the range of 90.16%–109.84% with relative standard deviation (RSD) not more than 4.77%. The method was easy to operate, accurate and highly reproducible, and could be suitable for the determination of 19 amino acids and taurine in formulas for special medical purpose intended for infants, providing strong technical support for enterprise quality control and government regulation.

A method for the determination of trimetazidine and clomiphene in animal-derived foods was developed by mixed-mode reversed-phase strong cation exchange solid phase extraction cleanup followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were extracted with 0.5% (V/V) formic acid in acetonitrile, and purified on a mixed-mode reversed phase strong cation exchange column (PRiME MCX). The chromatographic separation was performed on a Waters ACQUITY UPLC HSS T3 column by gradient elution using a mobile phase composed of acetonitrile and 0.1% formic acid. The analytes were detected in the positive ion mode using multiple reaction monitoring (MRM). Quantification was performed by the internal standard method. The results showed that good linearity was observed for trimetazidine and clomiphene in the concentration range of 0.3–100.0 ng/mL with determination coefficients (R²) > 0.999. The average recoveries of this method ranged from 93.4% to 112.1%, with relative standard deviations (RSDs) of 0.68%–4.81% (n = 6). The limit of detection (LOD) and the limit of quantitation (LOQ) were 0.1 and 0.3 μg/kg, respectively. The developed method is sensitive, stable, practical, and suitable for the determination of trimetazidine and clomiphene in animal-derived foods, which can provide effective technical support for food safety assurance for sports events.