Analysis of Pesticides Residue in Brown Rice by LCMS-8050RX - Comparison of On-Line Purification vs QuEChERS Methods

Importance of the Topic

Monitoring pesticide residues in staple foods such as brown rice is essential to meet strict regulatory limits and ensure consumer safety. Efficient multi-residue methods reduce analysis time, lower variability between operators, and minimize laboratory waste.

Objectives and Study Overview

This study compares two cleanup strategies for QuEChERS extracts of brown rice using an LCMS-8050RX platform:

• Traditional dispersive solid-phase extraction (dSPE)
• On-line purification via a Revive ILSP column integrated into the LC flow path

Performance metrics include recovery rates, reproducibility, calibration linearity, and cleanup efficiency for 164 pesticides.

Methodology and Instrumentation Used

Sample Preparation:

• 1.0 g ground brown rice + 1 mL water (15 min equilibration)
• Add 15 mL acetonitrile with 1 % acetic acid, shake
• Add QuEChERS extraction salts, shake and centrifuge
• Collect supernatant spiked to 2 ng/mL for cleanup comparison
• dSPE cleanup: PSA/C18/MgSO₄ kit
• ILSP cleanup: Revive ILSP Pesticides Single 5×2.1 mm cartridge inline column

Instrumentation:

• LCMS-8050RX with CoreSpray nebulizer
• Nexera X3 UHPLC and Shim-pack Velox Biphenyl column (100×2.1 mm, 2.7 µm)
• Mobile phases: 2 mM ammonium formate/0.002 % formic acid in water (A) and methanol (B)
• Gradient from 3 % to 100 % B over 12 min, 0.4 mL/min, 2 µL injection
• ESI in positive/negative MRM mode, DL 150 °C, block heater 300 °C

Key Results and Discussion

Calibration and Linearity:

• All compounds exhibited excellent linearity (R² > 0.996) over 0.5–50 ng/mL

Recovery and Reproducibility:

• dSPE: 98 of 164 pesticides recovered within 70–120 %
• ILSP: 130 of 164 pesticides recovered within 70–120 %
• %RSD was ≤ 20 % for the majority of analytes in both methods

Matrix Cleanup Efficiency:

• ILSP effectively removed co-eluting matrix interferences absent in dSPE data
• Cleaner baselines observed for critical compounds such as prochloraz and pyridaben

Benefits and Practical Applications

• On-line ILSP streamlines sample pretreatment by eliminating off-line cleanup steps
• Reduces plastic consumables and associated costs
• Improves consistency by minimizing operator-dependent variability
• Maintains or enhances recovery and reproducibility compared to dSPE

Future Trends and Potential Uses

Integration of inline purification columns is expected to expand to diverse food and environmental matrices. Future developments may include:

• Automation of sample handling for high-throughput laboratories
• Broader applicability to complex matrices such as soils and processed foods
• Development of multi-mode cleanup cartridges targeting additional classes of contaminants

Conclusion

The combination of QuEChERS extraction with an on-line Revive ILSP column on the LCMS-8050RX platform offers a fast, robust, and resource-efficient approach for multi-residue pesticide analysis in brown rice. On-line cleanup delivered comparable or superior performance to traditional dSPE while simplifying workflow and reducing waste.

Instrumentations Used

• LCMS-8050RX triple quadrupole mass spectrometer with CoreSpray neonizer
• Nexera X3 UHPLC system
• Shim-pack Velox Biphenyl column, 100 × 2.1 mm, 2.7 µm
• Revive ILSP Pesticides Single 5 × 2.1 mm cartridge (RESTEK P/N 27882)
• QuEChERS extraction salts kit (RESTEK P/N 26237)

References

1. Lupo S.A., Romesberg R.L., Lu X. Automated inline pigment removal for the analysis of pesticide residues in spinach by liquid chromatography tandem mass spectrometry. J. Chromatogr. A 1629 (2020), 461–477.