Quantitative Analysis of Amino Acids and Their Derivatives in Lucilia sericata Larval Excretions/Secretions Using Capillary Electrophoresis–Mass Spectrometry

A capillary electrophoresis-mass spectrometry (CE-MS) method was developed and validated for the determination of 19 amino acids and related compounds in excretions/secretions (ES) of Lucilia sericata larvae. Sample preparation consisted of dilution of ES with water, filtration and direct CE-MS analysis. Separation was performed with 50 mM formic acid as the background electrolyte, and methanol-water (1:1, v/v) containing 1% formic acid was used as sheath liquid. The total analysis time was 20 min. The method showed acceptable linearity, precision, accuracy, limit of detection (LOD), limit of quantification (LOQ), sensitivity, apparent recovery and short-term applicability for freshly prepared samples. Correlation coefficients for the calibration curves ranged from 0.983 to 0.998. Precision was within 18% at the lowest quality control level and within 15% at medium and high levels. Accuracy ranged from 83% to 118% at the lowest level and from 85% to 115% at the other levels. In larval ES, the most abundant compounds were threonine (565 ± 7 µM), tryptophan (455 ± 6 µM), anserine (404 ± 7 µM), histidine (330 ± 14 µM) and cystine (279 ± 4 µM). The method offers a simple workflow for targeted profiling of amino acids and related compounds in larval ES.