Quantitation of Pesticide Residues in Milk Using the Agilent 6470 Triple Quadrupole LC/MS

Importance of Topic

The widespread use of pesticides in agriculture can lead to their accumulation in dairy animals and subsequent transfer into milk fat. Regulatory bodies establish maximum residue limits based on fat content to protect consumers from lipophilic contaminants.

Objectives and Study Overview

This application note presents a streamlined workflow for quantifying carbofuran, carbendazim, benomyl, edifenphos, and 2,4-D in milk. The goal is to achieve high sensitivity, specificity, and reproducibility without extensive cleanup, reporting results relative to milk fat percentage.

Methodology and Instrumentation

• Sample Preparation: QuEChERS extraction of 10 mL milk, centrifugation, and direct transfer of supernatant.
• Chromatography: Agilent 1290 Infinity II LC with XDB C18 column (3.0 × 150 mm, 3.5 μm), gradient of 0.1% acetic acid in water and acetonitrile at 0.3 mL/min.
• Detection: Agilent 6470 triple quadrupole MS with AJS ESI in positive/negative polarity switching, using MRM transitions optimized for each analyte.
• Data Analysis: Agilent MassHunter software for qualitative review and quantitative processing with 1/x or 1/x2 weighting.

Main Results and Discussion

• Linearity: Matrix-matched calibration from 0.4 to 100 ng/mL yielded r^2 > 0.995 for all target compounds.
• Recoveries: At fat-based MRL levels, recoveries ranged from 84% to 95%, demonstrating accurate quantitation in complex milk matrix.
• Precision: Six replicate injections at 10 ppb showed %RSD below 2.5% for all analytes, confirming method repeatability.
• Benomyl Instability: Benomyl converted to carbendazim during analysis and was reported as carbendazim.

Benefits and Practical Applications

This QuEChERS LC/MS/MS protocol features rapid sample throughput, minimal solvent usage, and high sensitivity, making it suitable for routine quality control laboratories monitoring pesticide residues in dairy products to comply with regulatory standards.

Future Trends and Opportunities

Emerging advances may include automated sample preparation, integration with high-resolution mass spectrometry, expansion to a broader range of contaminants, and application of chemometric tools to improve data interpretation in complex matrices.

Conclusion

A robust polarity-switching MRM method on the Agilent 6470 reliably quantifies key pesticides in milk based on fat percentage. The approach balances ease of preparation with high analytical performance, supporting routine dairy safety testing.

Instrumentation Used

• Agilent 1290 Infinity II LC system
• Agilent 6470 triple quadrupole LC/MS
• Agilent XDB C18 column (3.0 × 150 mm, 3.5 μm)

References

• Comprehensive LC/MS/MS Workflow of Pesticide Residues in Food Using the Agilent 6470 Triple Quadrupole LC/MS System, Agilent Technologies application note 5994-2370EN (2020)
• Bedi JS et al. Pesticide residues in milk and their relationship with pesticide contamination of feedstuffs supplied to dairy cattle in Punjab, India. Journal of Animal and Feed Sciences, 2018, 27, 18–25