Organochlorine Pesticides, PCBs, and BFRs on Rxi®-XLB and Rxi®-17Sil MS (GCxGC-ECD)

Meaning of the topic

The simultaneous analysis of organochlorine pesticides, polychlorinated biphenyls (PCBs) and brominated flame retardants (BFRs) is critical for environmental monitoring, food safety, and regulatory compliance. These persistent, bioaccumulative compounds require highly selective and sensitive methods to detect trace levels in complex matrices. Comprehensive two-dimensional gas chromatography with electron capture detection (GC×GC-ECD) offers enhanced separation power and detection sensitivity, making it a valuable tool for laboratories focused on multiresidue analysis.

Objectives and Study Overview

The primary aim of this application note was to evaluate the performance of two GC columns (Rxi®-XLB and Rxi®-17Sil MS) in a GC×GC-ECD configuration for the separation of tri-class analytes (organochlorine pesticides, PCBs, BFRs). Key goals included:

• Assessing chromatographic resolution and peak capacity for target analytes.
• Optimizing modulation parameters to achieve rapid second-dimension separation.
• Demonstrating method applicability to standard mixtures of PBDEs, PCB congeners and organochlorine pesticides.

Methodology and Instrumentation

This study employed a dual-column GC×GC setup with hot-jet modulation and ECD detection. The main instrumentation and conditions were:

• Columns: Rxi®-XLB (30 m × 0.25 mm ID, 0.25 µm) as first dimension; Rxi®-17Sil MS (1 m × 0.15 mm ID, 0.15 µm) as second dimension with a 0.2 m guard segment.
• Carrier gas: Helium, constant flow at 2.0 mL/min.
• Modulator settings: Temperature offset +20 °C; separation time 3.5 s; hot pulse 1.25 s; cool time 0.50 s.
• Injection: 1 µL splitless, inlet at 250 °C, purge flow 20 mL/min.
• Detector: μ-ECD at 325 °C, data rate 50 Hz.
• Oven programs: Rxi®-XLB from 80 °C (1 min) to 120 °C at 10 °C/min then to 300 °C at 3 °C/min; Rxi®-17Sil MS from 85 °C (1 min) to 125 °C at 10 °C/min then to 305 °C at 3 °C/min.
• Samples: PBDE mix, PCB congener mix (Method 8082A), organochlorine pesticide mix; concentration 250 pg/µL in isooctane.

Main Results and Discussion

The GC×GC-ECD method achieved clear baseline separation of all target compounds within a total run time under 40 minutes. Key observations included:

• Enhanced resolution: The combination of mid-polarity and semi-polar columns resolved coeluting isomers and congeners.
• Efficient modulation: A 3.5 s modulation period provided distinct 2nd-dimension peaks without wrap-around.
• High sensitivity: μ-ECD detection delivered low-picogram detection limits for chlorinated pesticides and PCBs.

Benefits and Practical Applications

The described GC×GC-ECD workflow offers several advantages:

• Comprehensive screening: Simultaneous analysis of multiple contaminant classes in a single run.
• Regulatory compliance: Suitable for environmental monitoring, food safety and QA/QC laboratories.
• Analytical robustness: Reproducible retention times and peak shapes across complex mixtures.

Future Trends and Potential Uses

Advancements likely to enhance this methodology include:

• Integration with high-resolution mass spectrometry for confirmation of unknowns.
• Automated data processing algorithms for faster deconvolution and quantitation.
• Miniaturized or portable GC×GC platforms for on-site environmental assessments.

Conclusion

The evaluated GC×GC-ECD approach on Rxi®-XLB and Rxi®-17Sil MS columns provides a powerful and sensitive solution for multiresidue analysis of organochlorine pesticides, PCBs and BFRs. Its robust separation performance and low detection limits make it ideal for laboratories working on environmental and food safety monitoring.

Reference

Restek Corporation Application Note GC_EV1243, Bellefonte, PA.