Determination of pesticides in foods using phosphorus and sulfur detection by GC-ICP-QQQ

Significance of the Topic

The monitoring of pesticide residues in foods is critical to protect public health, particularly for sensitive populations such as infants and children. Many organophosphorus and organosulfur pesticides pose endocrine‐disrupting risks even at low levels, driving the need for analytical methods that combine rapid sample preparation with highly selective and sensitive detection.

Goals and Study Overview

This application note evaluates the coupling of gas chromatography to triple-quadrupole inductively coupled plasma mass spectrometry (GC-ICP-QQQ) for selective determination of phosphorus (P) and sulfur (S) heteroatoms in pesticide residues. The study aims to assess linearity, detection limits, and applicability to real food matrices using a QuEChERS sample-prep approach.

Methodology

Samples of baby‐food purees and various teas were homogenized and extracted via the AOAC 2007.01 QuEChERS protocol. The extracts were cleaned with dispersive SPE, then analyzed by GC-ICP-QQQ in MS/MS mass-shift mode using O2 cell gas. P and S were quantified as 31PO+ at m/z 47 and 32SO+ at m/z 48 respectively.

Applied Instrumentation

• Agilent 7890 GC coupled to Agilent 8800 ICP-QQQ with GC-ICP-MS interface (G3158D)
• First column: 5 m × 0.18 mm × 0.18 µm DB-35ms Ultra Inert capillary
• Second column: 15 m × 0.25 mm × 0.25 µm DB-5MS Ultra Inert capillary
• Splitless injection (1 µL) at 280 °C; pre-heated makeup gas
• ICP-QQQ tuning with H2S-spiked argon; optimized O2 reaction cell conditions

Key Results and Discussion

Calibration for P (0.01–16 µg/L) and S (0.8–33 µg/L) yielded correlation coefficients > 0.997 for 18 pesticides. Detection limits for P‐containing pesticides ranged from 0.02 to 0.9 µg/L (as compound) and 0.02 to 0.4 µg/L (as element), comparable or superior to GC-MS/MS. S‐based limits were within typical GC/MS/MS performance. Mixed‐standard and real‐sample chromatograms confirmed selective heteroatom detection and identification of multiple organophosphorus residues in baby foods and teas.

Benefits and Practical Applications

• High selectivity and reduced spectral interferences through MS/MS reaction cell
• Low background for P and S enabling sub-µg/L quantitation
• Orthogonal heteroatom detection complements GC-MS/MS workflows
• Applicable to diverse matrices with QuEChERS sample prep

Future Trends and Applications

• Extension to other heteroelements (Cl, Br) for flame retardants and additives
• Routine monitoring of chemical warfare agents and polymer contaminants
• Automation of sample prep and data analysis in high-throughput labs
• Advanced cell gases and hardware refinements to minimize residual backgrounds

Conclusion

GC-ICP-QQQ provides a robust platform for selective, sensitive heteroatom detection of organophosphorus and organosulfur pesticides in food. Its low detection limits, strong linearity, and compatibility with standard QuEChERS workflows make it a viable alternative or complement to established GC-MS/MS methods for food-safety applications.

References

1. S. J. Lehotay et al., "Determination of pesticide residues in foods by acetonitrile extraction and partitioning with magnesium sulfate," J AOAC Int., 90(2), 485-520 (2007).
2. P. L. Wylie, C. Meng, "A Method for the Trace Analysis of 175 Pesticides Using the Agilent Triple Quadrupole GC/MS/MS," Agilent publication 5990-3578EN (2009).
3. M. Churley, Agilent Technologies, "Application Note 5991-4131EN" (2014).