Analysis of Dithiocarbamate Pesticides by GC-MS

Importance of the topic

Dithiocarbamate fungicides are among the most widely applied crop protection agents worldwide. Their broad efficacy, low acute mammalian toxicity, and cost-effectiveness make them indispensable in modern agriculture. However, their rapid degradation to carbon disulfide (CS₂) and toxic by-products poses analytical challenges for food safety and regulatory compliance.

Objectives and study overview

This work presents a validated, routine method for quantifying total dithiocarbamate residues in fruits and vegetables. By converting all dithiocarbamate species to CS₂ via SnCl₂/HCl hydrolysis and using GC-MS analysis, the goal is to achieve high sensitivity, precision, and robust recovery across diverse matrices.

Methodology and instrumentation

Sample preparation employs acid hydrolysis in closed bottles at 80 °C, extracting liberated CS₂ into iso-octane. After centrifugation, the organic phase is analyzed by GC-MS in SIM mode monitoring m/z 76 and 78.

• Gas chromatograph: Thermo Scientific™ TRACE GC Ultra™ with Triplus™ RSH autosampler
• Mass spectrometer: Thermo Scientific™ ITQ™ 900 ion trap (SIM, EI 70 eV)
• Columns tested: mid-polarity TraceGOLD™ TG-624 and low-polarity TG-5MS
• Detection limits: LOD 0.005 µg/mL, LOQ 0.04 µg/mL

Main results and discussion

The method shows excellent linearity (0.04–1.30 µg/mL CS₂, R² > 0.999). Matrix-matched recoveries in grapes, chili, potato, eggplant, and tomato ranged from 79 % to 104 % with repeatability and intermediate precision within acceptable limits. Potential interferences from brassica crops are noted due to endogenous CS₂ precursors. Avoidance of rubber materials prevents false positives.

Benefits and practical applications

This streamlined procedure delivers:

• Single-sum measurement of all dithiocarbamates
• High throughput: 1–2 h sample preparation
• Compatibility with standard GC columns and autosamplers
• Applicability across a broad range of produce

Future trends and potential applications

Emerging directions include coupling hydrolysis-GC-MS with high-resolution mass spectrometry for compound-specific identification and adapting the workflow to triple quadrupole platforms for enhanced selectivity. Integration into automated sample processors and expansion to processed foods are prospective developments.

Conclusion

The described SnCl₂/HCl hydrolysis followed by GC-MS provides a reliable, validated approach for total dithiocarbamate residue analysis in diverse fruits and vegetables. Its sensitivity, precision, and ease of implementation make it suitable for regulatory laboratories and quality control settings.

References

[1] Crnogorac G., Schwack W. Trends Anal. Chem. 2009, 28(1).
[2] Reynolds S. SELAMAT Workshop, Bangkok 2006.
[3] Eurl SRM Method (Dithiocarbamates CS₂).
[4] Amvrazi E.G. in Pesticides – Formulations, Effects, Fate, 2011.