Initial Work for Automation of Organo Chlorine Pesticides and Poly Chlorinated Biphenyls in Water

Significance of the Topic

The reliable determination of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in water is essential for environmental monitoring, regulatory compliance, and public health protection. Automated sample preparation and analysis reduce human error, increase laboratory efficiency, and support high-throughput testing demands.

Objectives and Study Overview

This work aimed to develop and evaluate an on-line, automated liquid-liquid extraction (LLE) workflow for 39 OCPs and 19 PCBs in water. The study focused on miniaturizing the conventional method, optimizing solvent usage, and integrating key instrumentation to improve throughput, sensitivity, and reproducibility.

Instrumentation

• Dual Head GERSTEL MPS XT autosampler
• GERSTEL Agitator for automated mixing
• Anatune CoolRPLUS rapid GC oven cooling
• GERSTEL Cooled Injection System (CIS)
• Agilent 7890 GC coupled to 5977B mass spectrometer with High Efficiency Source (HES)
• Maestro control software integrated workflow

Methodology and Instrumentation

Samples of 18 mL water were extracted with 500 µL of iso-hexane:acetone (95:5) in 20 mL vials. The GERSTEL Agitator mixed samples at 750 rpm, and a small polar solvent addition broke emulsions. A 10 µL aliquot of the organic layer was directly injected into the CIS by large volume injection to compensate for the reduced extraction scale. Calibration standards (5, 25, 50, 100 ng/L) were prepared by automated spiking of concentrated stock solutions. Initial full-scan runs established retention times, followed by Selected Ion Monitoring (SIM) for quantification on a 30 m DB-5MS UI column.

Main Results and Discussion

The automated workflow doubled sample throughput, enabling 44 injections per 24 h using the PrepAhead function. Compared to manual LLE, the method saved 3 900 analyst hours per year and reduced solvent consumption by over 160 L annually. The HES source provided a 20–50× sensitivity increase over traditional sources. Linearity for trifluralin yielded R²=0.9997, and internal standard (trifluralin-d14) reproducibility showed 5.5 % RSD. Some low-level compounds required further optimization due to blank noise and column age.

Benefits and Practical Applications of the Method

• 100 % increase in throughput and significant analyst time savings
• Reduced solvent usage, storage, and disposal costs
• Minimized human pipetting errors and health risks
• Consistent, accurate, and reproducible data
• Lower instrument maintenance requirements

Future Trends and Potential Applications

Further enhancements may include integrating automated centrifugation to address emulsions, exploring larger injection volumes, refining extraction parameters, and extending the approach to complex matrices. Advances in source design and software scheduling could further boost sensitivity and throughput.

Conclusion

This study demonstrates the feasibility of automating and miniaturizing LLE for OCPs and PCBs in water while achieving high sensitivity, reproducibility, and significant resource savings. Continued optimization will expand compound coverage and support routine environmental monitoring applications.