Benefits of EMR—Lipid Cleanup with Enhanced Post Treatment on Pesticides Analysis by GC/MS/MS

Importance of the Topic

The reliable detection of pesticide residues in high-fat foods such as avocado is crucial for food safety monitoring. Traditional QuEChERS workflows often leave lipid and water residues that impair GC/MS/MS performance, especially for labile analytes. The development of advanced sorbent materials and post-treatment steps addresses these challenges by improving sample cleanliness and analytical reproducibility.

Objectives and Study Overview

This study evaluates a modified sample preparation protocol combining Agilent Bond Elut EMR-Lipid cleanup with an enhanced post-treatment step using anhydrous MgSO4. The goals are to assess improvements in GC/MS/MS response, peak shape, system reproducibility, and maintenance of matrix removal efficiency and analyte recovery in avocado matrices, focusing on four labile pesticides.

Methodology

The procedure follows a standard QuEChERS extraction, followed by EMR-Lipid dispersive SPE. The innovation lies in a post-cleanup polish and drying step:

• Decant acetonitrile extract into a tube containing EMR-Lipid sorbent
• Add polishing salts and mix, then separate phases
• Transfer extract to a preweighed tube with 300 mg anhydrous MgSO4
• Centrifuge to remove residual water and water-soluble residues
• Transfer cleaned aliquot to vials for GC/MS/MS analysis

Used Instrumentation

• Agilent 7890A GC with 7693B autosampler and 7000C Triple Quadrupole MS
• Agilent J&W DB-5ms column with backflushing capability
• GenoGrinder, CentraCL3R and Eppendorf centrifuges
• Vortexers, pipettes, and EMR-Lipid dSPE and EMR-MgSO4 pouches

Key Results and Discussion

The enhanced post-treatment delivers a 3- to 10-fold increase in signal for labile pesticides and produces sharper, more symmetric peaks, facilitating data processing. Over 100 injections of avocado samples, relative standard deviations for most analytes fell below 10%, compared to up to 70% RSD with traditional PSA/C18 cleanup. Both splitless and dimple liners remained virtually free of residue, indicating extended instrument maintenance intervals. Matrix removal efficiency remained at ∼80%, and pesticide recoveries averaged within acceptable ranges with enhanced repeatability below 5% RSD.

Benefits and Practical Applications

• Significantly improved analytical reproducibility for labile pesticides
• Enhanced GC/MS/MS sensitivity and peak shape
• Extended inlet liner and column lifetime with reduced maintenance
• High lipid and water removal compatible with strict regulatory criteria

Future Trends and Opportunities

Further refinements may integrate automated post-treatment modules to streamline workflows. Applying similar strategies to other challenging matrices, such as high-fat animal tissues, could broaden the technique’s impact. Advances in sorbent design and micro-scale drying protocols may further reduce solvent consumption and improve throughput.

Conclusion

The modified EMR-Lipid cleanup with enhanced MgSO4 post-treatment offers a robust, high-throughput approach for fatty samples by GC/MS/MS. It combines superior water and lipid removal with excellent analyte recovery and system stability, meeting rigorous food safety testing requirements.

Reference

1 Anastassiades M et al Fast and easy multiresidue method employing dispersive SPE for pesticide analysis J AOAC Int 2003 86 412
2 Lehotay SJ et al Buffering strategies to improve problematic pesticides in QuEChERS J AOAC Int 2005 88 615
3 Chamkasem N et al Analysis of pesticides in avocado Using modified QuEChERS J Agric Food Chem 2013 61 2315
4 Hildmann F et al Pesticide residues in chicken eggs sample prep for GC and LC J Chromatogr A 2015 1403 1