Monitor Organophosphorus Pesticides in Air, Using ORBOTM-49P Tubes and Capillary GC

Significance of the Topic

Monitoring airborne organophosphorus pesticides is critical for protecting worker health and ensuring environmental safety. These compounds, widely used in agriculture and vector control, pose inhalation risks at low concentrations. A robust analytical approach enables accurate exposure assessment, regulatory compliance, and timely intervention.

Study Objectives and Overview

This application note evaluates a unified sampling and analysis procedure for five organophosphorus pesticides (chlorpyrifos, diazinon, dichlorvos, malathion, parathion) in vapor and aerosol forms using ORBO™-49P adsorbent tubes and capillary gas chromatography with flame photometric detection (GC-FPD). The goal is to confirm desorption efficiency, detection limits, and practical sampling volumes under workplace conditions.

Instrumentation Used

• ORBO™-49P adsorbent tubes (270 mg Supelpak-20 resin front bed, 140 mg backup bed, glass fiber filter, polyurethane foam plugs)
• Gas chromatograph with flame photometric detector (FPD)
• SPB-20 fused silica capillary column (60 m × 0.53 mm ID, 1.0 µm film)
• Helium carrier gas, toluene desorption solvent containing tributyl phosphate internal standard

Methodology and Procedure

Air is drawn at 1.0 L/min through ORBO-49P tubes for up to 8 hours (480 L) for all analytes except malathion (60 L). Both vapor and aerosol phases are captured: resin retains vapors, fiber filter traps aerosols. Tubes are desorbed with 2.0 mL toluene containing 78 µg/mL tributyl phosphate. Front and backup beds plus filter media are analyzed separately. GC conditions: injector at 220 °C, oven ramp from 200 °C (2 min) to 250 °C at 4 °C/min, FPD at 300 °C, helium flow 8 mL/min, 1 µL splitless injection.

Main Results and Discussion

Desorption efficiencies exceeded 94 % for all pesticides, matching or surpassing OSHA data. Reliable quantitation limits range from 0.92 µg/sample (dichlorvos) to 1.8 µg/sample (malathion), corresponding to 0.21–2.2 ppb in air. Breakthrough was negligible under recommended volumes, and high humidity (80 % RH) did not impair retention. GC analysis resolved five compounds in under 13 minutes with acceptable background levels.

Benefits and Practical Applications

• Single-tube sampling simplifies field collection without tandem filters or adsorbents.
• Simultaneous capture of vapor and aerosol improves representativeness of workplace air.
• High sensitivity and rapid analysis support compliance monitoring at action levels.
• Compatible with OSHA Method 62 and related procedures for other pesticides.

Future Trends and Potential Applications

Advances may include portable GC systems, real-time sensor integration, and expanded tubing formulations for broader pesticide classes. Automation of desorption and data processing could further streamline large-scale exposure assessments. Miniaturized samplers and on-site analysis modules may enable continuous monitoring in agricultural and industrial environments.

Conclusion

The combination of ORBO-49P adsorbent tubes and SPB-20 GC-FPD provides a reliable, high-throughput method for monitoring key organophosphorus pesticides in air. Its simplicity, sensitivity, and robustness make it well suited for occupational safety and environmental surveillance.

References

1. OSHA Analytical Methods Manual, Method 62. Organic Methods Evaluation Branch, OSHA Analytical Laboratory, Salt Lake City, Utah, USA (Oct. 1986).