Optimization of liquid chromatography and mass spectrometry parameters based on LC-QQQ: A case study on lysinoalanine

Lysinoalanine (LAL), commonly formed in high-protein foods, raises concerns due to its nephrotoxicity and potential reduction in nutritional properties, making its accurate detection crucial for food safety. Liquid chromatography-tandem quadrupole mass spectrometry (LC-QQQ) plays a pivotal role in the quantification of compounds, and its accuracy and sensitivity are significantly influenced by specific liquid chromatography (LC) and mass spectrometry (MS) parameters. However, the procedure and considerations for LC and MS parameters optimization have often not been discussed in depth in existing literature. Therefore, this study used LAL as a model compound to systematically optimize the key LC and MS parameters using LC-QQQ. The optimized MS parameters were as follows: parent ion m/z-234.2, capillary voltage-3.5 kV, cone voltage-30 V, desolvation temperature-500 °C, daughter ion m/z-84.2, and collision voltage-20 V. The optimized LC parameters were as follows: buffer-0.1 % formic acid (v/v), column, Polaris 3 Amide-C18 (150 × 3 mm, 3 μm). Under these optimized conditions, the limit of detection (LOD) for LAL was detected as 13 ng/mL in multiple reaction monitoring mode, which is considerably lower than the 125 ng/mL detected by LC-QQQ and marginally lower than the 15.23 ng/mL detected by LC-quadrupole Exactive Orbitrap MS reported in previous studies. Additionally, this study elucidates the critical factors to be considered when selecting LC and MS parameters, providing valuable insights into the detection of other compounds using LC-QQQ.