Sensitive and Repeatable Analysis of Pesticides in QuEChERS Extracts with APGC-MS/MS

Significance of the Topic

The routine monitoring of pesticide residues in food is critical for consumer safety and regulatory compliance. Multi residue methods face challenges from low detection limits, diverse sample matrices and a growing list of pesticide compounds. Soft ionization approaches can improve sensitivity for difficult analytes.

Study Objectives and Overview

This study evaluates an integrated workflow combining QuEChERS sample preparation and atmospheric pressure gas chromatography tandem mass spectrometry (APGC-MS/MS) on a single platform to analyze GC amenable pesticides in strawberry, pear and spinach. The goal is to demonstrate enhanced sensitivity, selectivity and repeatable quantitation for twenty challenging pesticides.

Methodology and Instrumentation

Ultrafast GC separation was performed on a capillary DB5 column with helium as carrier gas and a temperature program from 70 to 300 C. APGC provided soft ionization favoring proton transfer to generate abundant molecular ions. Tandem MS analysis employed multiple reaction monitoring with optimized cone voltages and collision energies. Key steps included matrix matched calibration, deuterated injection standard addition, and replicate measurements across three days.

Used Instrumentation

• Waters 7890A gas chromatograph
• DB5-MS capillary column 30 m x 0.25 mm x 0.25 um
• Xevo TQ-S triple quadrupole mass spectrometer with interchangeable APGC and ESI sources
• DisQuE QuEChERS CEN method 15662 sample preparation kit
• TargetLynx application manager for data processing

Main Results and Discussion

Calibration curves for endosulfan sulphate and other pesticides showed linear responses from 0.05 to 50 ng per mL with R2 above 0.99 and residuals below 15 percent. Limits of detection ranged between 0.01 and 0.5 ng per mL, meeting or exceeding regulatory requirements. Spike recoveries at 1 ug per kg in three matrices achieved accuracy within 5 percent and precision under 5 percent RSD across ten replicates. APGC soft ionization significantly improved the abundance of parent ions compared to traditional electron ionization.

Benefits and Practical Applications

• Single MS platform for both GC and LC amenable pesticides simplifies laboratory workflows
• High sensitivity and selectivity enable detection of low level residues in complex matrices
• Reduced matrix interference through sample dilution extends instrument maintenance intervals
• Robust repeatability supports routine quantitative analysis in QA QC and research laboratories

Future Trends and Opportunities

The demonstrated performance of APGC MS MS suggests broader adoption for pesticide residue screening and confirmation. Future developments may include expanded multiresidue panels, faster chromatography, and integration with high throughput automation. Soft ionization techniques could also be applied to other semi volatile contaminants.

Conclusion

APGC MS MS on a Xevo TQ S with QuEChERS extracts delivers sensitive, repeatable quantitation of twenty challenging pesticides in fruit and vegetable matrices. The approach exceeds conventional EI based methods in sensitivity and specificity, supporting regulatory compliance and operational efficiency.

References

• Portoles T Cherta L Beltran J Hernandez F Investigation of APGC for soft ionization in pesticide residue analysis J Chromatogr A 1260 183 2012