Simultaneous Analysis of 66 Pesticides by GC-MS Using Hydrogen Carrier Gas

Significance of the topic

The increasing scarcity and rising cost of helium have spurred the exploration of hydrogen as an alternative carrier gas in gas chromatography-mass spectrometry (GC-MS). Using hydrogen offers potential benefits in cost savings and supply stability while maintaining analytical performance in routine pesticide monitoring for environmental, agricultural, and food safety applications.

Objectives and overview of the study

This study evaluates the performance of hydrogen carrier gas for simultaneous analysis of 66 pesticides using the Shimadzu GCMS-QP2010 Ultra. Key aims include comparing spectral integrity, sensitivity, and repeatability against traditional helium gas under standardized conditions.

Methodology and instrumentation

The analytical method employed a 30 m × 0.25 mm i.d. Rtx-5MS column with a 0.25 µm film thickness. Standard mixtures at 0.005 and 0.5 mg/L were prepared in methylene chloride. Injection was performed in splitless mode (250 °C, 2 µL) under high pressure, and the oven temperature ramped from 80 °C to 280 °C. Mass spectra were recorded in scan (m/z 70–360, 0.5 s/event) and SIM modes (0.3 s/event) monitoring characteristic ions for each compound.

Used Instrumentation

• Shimadzu GCMS-QP2010 Ultra with Dual Inlet Turbo Molecular Pump
• Rtx-5MS capillary column (30 m × 0.25 mm i.d., 0.25 µm film)
• Custom SkyLiner splitless glass liner
• Hydrogen and helium carrier gases
• Mass spectrometer interface at 250 °C and ion source at 230 °C

Main results and discussion

• Mass spectral patterns for representative pesticide dichlorvos showed no alteration when using hydrogen, indicating spectral stability across all 66 compounds.
• Sensitivity in SIM mode decreased with hydrogen carrier gas due to elevated chromatographic baseline, resulting in lower signal-to-noise ratios compared to helium (e.g., S/N for dichlorvos dropped from 490 to 66).
• Despite reduced sensitivity, repeatability at 0.005 mg/L was satisfactory. Relative standard deviations (%RSD) for all analytes remained below 10%, demonstrating robust quantitative performance.

Benefits and practical applications

Switching to hydrogen carrier gas can alleviate helium supply constraints and reduce operational costs. The validated method maintains acceptable spectral fidelity and reproducibility, making it suitable for routine pesticide residue screening in environmental, food safety, and regulatory laboratories.

Future trends and opportunities

• Integration of hydrogen generators and safety systems to streamline laboratory workflows and minimize handling risks.
• Method refinement to improve baseline stability and sensitivity through optimized flow control and column technologies.
• Expansion to multiclass contaminant panels and coupling with high-resolution mass spectrometry for enhanced selectivity.

Conclusion

The GCMS-QP2010 Ultra with hydrogen carrier gas delivers reliable simultaneous analysis of 66 pesticides, preserving spectral integrity and offering satisfactory repeatability despite lower sensitivity relative to helium. Laboratories can consider hydrogen as a viable alternative carrier gas, subject to safety measures and performance verification.