Comparative evaluation of QuEChERS method with LC-MS/MS for three pesticides; novaluron, dimethomorph, and iprodione

This study aims to enhance the efficiency of field inspection centers, which require rapid testing and swift distribution control of non-compliant agricultural products. Currently, these centers in Korea use Multi-Residue Pesticide Test Method No. 2 to simultaneously analyse 510 pesticides. While 470 pesticides can be quantified using this method, others require additional quantification using individual test methods. Novaluron, dimethomorph, and iprodione, pesticides frequently exceed maximum residue limits, must be quantified using Individual Test Method No. 22 when detected by Method No. 2. This study validated and compared the effectiveness of these two methods for analysing the three pesticides in four agricultural matrices-lettuce, chili pepper, Welsh onion, and mandarin-by assessing specificity, linearity, detection and quantification limits, matrix effect, recovery rates, and repeatability. LC-MS/MS analysis showed both methods demonstrated high specificity and separation efficiency, with a coefficient of determination (R² > 0.99). LOQ values for vegetables were below 0.01 mg/kg, meeting regulatory standards; however, for mandarin, Method No. 2 exceeded the limit (0.02 mg/kg), while Method No. 22 remained within range. For vegetables recovery rates were slightly better with Method No. 22, but met validation criteria for both methods. In mandarin, recovery rates did not meet the validation criteria with Method No. 2. Novaluron at 0.02 mg/kg exceeded the acceptable RSD limit (23% vs. 20%), while iprodione showed slightly elevated RSD but remained acceptable. All other results met validation criteria. In conclusion, Method No. 2 was validated for quantifying the three pesticides in vegetables, demonstrating its potential application in field inspections. Monitoring of 1,744 agricultural samples revealed seven cases (0.4%) exceeding residue limits, including dimethomorph in basil (3 cases) and coriander (1 case) and iprodione in carrot (2 cases) and chard (1 case). Additionally, 46 cases (2.6%) were detected within acceptable limits, including novaluron (2 cases), dimethomorph (42 cases), and iprodione (2 cases).for mandarin samples did not meet the criteria in Method No. 2.