Method for the determination of 182 Residual Pesticides in Milk using LCMS-8045 and GCMS-TQ8040 NX

Significance of the topic

Milk is a vital nutritional source especially for infants and children, but its complex matrix can harbor pesticide residues from contaminated feed or water. Regulatory agencies set stringent maximum residue limits in milk, often lower than those for fruits and vegetables, creating a demand for sensitive and reliable analytical methods.

Objectives and overview of the study

The study aimed to develop and validate a rapid, high-throughput workflow for the simultaneous determination of 182 pesticides in milk. A multi-residue method combining modified QuEChERS extraction with ultrafast LC-MS/MS and GC-MS/MS was optimized to meet global regulatory requirements including FSSAI limits.

Methodology and instrumentation

Sample preparation employed a modified QuEChERS protocol with acetonitrile deproteinization, partitioning by anhydrous MgSO4, and dual cleanup steps using C18 sorbent. Part of the extract was subjected to LC-MS/MS analysis, the remainder to GC-MS/MS after solvent exchange.

• LC-MS/MS: Shimadzu LCMS-8045 with Nexera X2, Shim-pack XR-ODS II column; gradient of ammonium formate and methanol with formic acid, flow rate 0.3 mL/min, run time 20 min, injection volume 10 µL.
• GC-MS/MS: Shimadzu GCMS-TQ8040 NX with AOC-20i+s injector, SH-Rxi-5Sil MS column; helium carrier, splitless injection of 2 µL, temperature program from 60 °C to 310 °C over 25 min.
• Data processing: LabSolutions Insight software, Shimadzu pesticide method package and Smart Pesticides Database for fast MRM optimization.

Key results and discussion

Validation followed SANTE guidelines covering specificity, linearity, recovery, repeatability and reproducibility. Calibration was linear from 1–20 µg/L (extended to 2–40 µg/L for certain analytes). Limits of quantification (LOQs) of 5 µg/kg were achieved for 101 LC-amenable and 73 GC-amenable pesticides; the remaining 31 analytes had LOQ of 10 µg/kg.

• Recovery ranged between 70 % and 120 % for most compounds; a subset fell between 35 % and 70 %.
• Precision (RSDr and RSDR) was within 20 % at LOQs for all analytes.
• Method covered 113 pesticides by LC-MS/MS, 92 by GC-MS/MS, including 61 of 66 FSSAI targets.

Benefits and practical applications of the method

The proposed workflow delivers high throughput through short run times, minimal sample handling and robust quantification. It supports routine QA/QC testing in dairy laboratories, ensuring compliance with stringent residue regulations.

Future trends and potential applications

Further developments may include extension to other dairy matrices, integration of high-resolution MS, on-line sample cleanup automation, expansion of analyte databases and adaptation to evolving regulatory lists.

Conclusion

The validated multi-residue method combines modified QuEChERS extraction with ultrafast LC-MS/MS and GC-MS/MS to sensitively quantify a broad spectrum of pesticides in milk. It demonstrates excellent accuracy, precision and throughput, making it suitable for regulatory compliance testing.

References

• GB 2763-2019 National Food Safety Standard—Maximum Residue Limits for Pesticides in Food.
• Anastassiades M, Lehotay SJ, Štajnbaher D, Schenck FJ, Fast and Easy Multiresidue Method Employing Acetonitrile Extraction/Partitioning and Dispersive Solid-Phase Extraction for the Determination of Pesticide Residues in Produce, J AOAC Int., 86, 412–431 (2003).
• Guidance document on analytical quality control and method validation procedures for pesticide residues and analysis in food and feed. SANTE/12682/2019.