Optimization of Pirimicarb and Its Metabolites by Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry

Pesticides enhance crop productivity but leave residues that threaten the health and the environment, necessitating sensitive analytical methods to detect widely used compounds like pirimicarb. This study focuses on optimizing the analysis of pirimicarb and its metabolites using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Key instrumental parameters including interface temperature, desolvation line temperature, heat block temperature, column oven temperature, collision-induced dissociation (CID) gas pressure, and interface voltage were systematically optimized to enhance method sensitivity and reliability. Among the tested conditions, interface temperatures of 150 °C and 400 °C provided the highest signal intensity for pirimicarb, while pirimicarb-desmethyl responded best at 250 °C, and pirimicarb-desmethyl-formamido showed maximum signals at 150 °C and 300 °C. For desolvation line temperature, 150 °C yielded the highest intensities for pirimicarb and pirimicarb-desmethyl, whereas 200 °C was optimal for pirimicarb-desmethyl-formamido. Pirimicarb exhibited peak response at a heat block temperature of 300 °C, while pirimicarb-desmethyl showed comparable intensities at 100, 200, and 350 °C, and pirimicarb-desmethyl-formamido responded best at 100 and 200 °C. Column oven temperatures of 40 °C and 50 °C enhanced the response for pirimicarb, with pirimicarb-desmethyl and pirimicarb-desmethyl-formamido showing optimal intensities at 50 °C. Additionally, a CID gas pressure of 270 kPa and interface voltage of 4.0 kV produced the highest ionization efficiency across all analytes. The results demonstrated that specific parameter adjustments significantly improved ionization efficiency and signal intensity, leading to a more robust analytical method. This study underscores the importance of systematic parameter optimization in LC-MS/MS for accurate pesticide residue detection and provides a framework for future research on other pesticide groups.