A New GC Interface for Sector Field ICP-MS

Significance of the topic

The accurate speciation and quantification of trace mercury and organotin compounds in surface waters is critical for environmental monitoring and regulatory compliance. Upcoming amendments to the EU Water Framework Directive will impose stringent ppt and sub-ppt limits for toxic species such as methylmercury and tributyltin. Achieving these low detection limits requires advanced analytical interfaces that combine high sensitivity with robust operation.

Objectives and overview

This study evaluates a newly developed gas chromatograph interface for the Thermo Scientific ELEMENT 2/XR sector field ICP-MS system. The goal is to compare its performance with the existing GC-XSERIES 2 coupling in terms of sensitivity, detection limits, chromatographic fidelity, and suitability for trace speciation of mercury and tin species in environmental samples.

Methodology and instrumentation

Derivatization and sample preparation involved ethylation and propylation of target species followed by headspace extraction from 40 mL water samples. The sealed vials were agitated, and the organic phase was transferred to GC vials after centrifugation for enriched recovery studies.

• Gas chromatograph: TRACE GC Ultra™ with modified ELEMENT 2/XR torchbox for dual gas and aerosol introduction
• Capillary column: TR-5, 30 m × 0.25 mm, 25 µm film thickness
• Injection: Programmable temperature vaporizer, splitless, 1 µL at 250 °C with ramp to 400 °C
• Carrier gas: Helium at 3 mL min⁻¹
• Nebulizer and spray chamber: Concentric impact bead with Ar at 600 mL min⁻¹
• ICP-MS: ELEMENT 2/XR sector field operating at 1400 W with on-line mass bias correction

Key results and discussion

The new interface delivered a fivefold increase in peak intensity for mercury species compared to the GC-XSERIES 2, with typical limits of detection improved by 2–5 times. Chromatograms from both systems exhibited identical peak shapes and retention times. Measured limits of detection for MeHg⁺ and Hg²⁺ approached sub-ppt levels using only 40 mL sample volumes. Field samples from ponds, lakes, and nature reserves showed MeHg⁺ and Hg²⁺ concentrations below regulatory limits, while some butyltins were detected at low ng L⁻¹ levels. Spike recovery ranged from 110 % to 180 %, indicating efficient derivatization and extraction.

Benefits and practical applications

The enhanced sensitivity and stability of the ELEMENT 2/XR interface allow for reliable speciation at ultra-trace levels with minimal sample volume. Easy setup and tuning, combined with on-line internal standard addition, support routine environmental monitoring, QA/QC in industrial labs, and research applications requiring robust quantification of toxic elemental species.

Future trends and potential applications

Further improvements may include the use of cleaner reagents to reduce background tin, optimization of derivatization protocols for broader organotin species, and scaling to larger sample volumes for even lower detection limits. Integration with automated sample preparation and coupling with other chromatographic techniques could expand applicability to additional trace metal speciation workflows.

Conclusion

The new GC interface for the ELEMENT 2/XR sector field ICP-MS demonstrates superior sensitivity, robust operation, and low detection limits for mercury and tin speciation in environmental waters. Its performance meets the requirements of forthcoming regulatory standards while maintaining ease of use and minimal sample volume.

Reference

No external literature references were provided in the source document.