Speciation of Trace Elemental Species using GC-ICP-MS and GC-HR-ICP-MS

Importance of the Topic

Speciation analysis of trace elements is essential for accurate assessment of toxicity, bioavailability, mobility and reactivity in environmental, industrial and biochemical contexts. Regulatory requirements such as the EU Water Framework Directive demand ultra-trace detection of organotins, methylmercury and brominated flame retardants at sub-ng/L levels, which can only be met by sensitive speciation techniques.

Objectives and Study Overview

This application note evaluates two gas chromatography–inductively coupled plasma mass spectrometry (GC-ICP-MS) configurations for the speciation of mercury and tin species. The performance of a quadrupole ICP-MS (XSERIES 2) and a sector-field ICP-MS (ELEMENT 2) coupled to a TRACE GC Ultra is compared in terms of chromatographic reproducibility, sensitivity and detection limits.

Methodology and Instrumentation

Sample derivatization involved reaction of tin species with sodium tetraethylborate in hexane/acetate buffer. GC separation used a TRACE Tr-5 column (30 m × 0.25 mm ID, 25 µm) with PTV splitless injection and He carrier gas. Both ICP-MS instruments were operated under matched conditions: XSERIES 2 in high-sensitivity mode and ELEMENT 2 with X-cones. External aqueous standards were introduced simultaneously via a dual-mode GC interface to ensure plasma stability and allow direct calibration.

Used Instrumentation

• Thermo Scientific TRACE GC Ultra
• Thermo Scientific XSERIES 2 Quadrupole ICP-MS with GC coupling kit
• Thermo Scientific ELEMENT 2 Sector-Field ICP-MS with GC coupling kit

Main Results and Discussion

Chromatograms from both systems showed identical peak shapes and retention times for Hg and Sn species. The ELEMENT 2 exhibited an eightfold higher signal intensity compared to the XSERIES 2. Calibration curves for monobutyltin and dibutyltin displayed excellent linearity. Limits of detection calculated from blank measurements were substantially lower on the ELEMENT 2, demonstrating its suitability for ultra-trace applications.

Benefits and Practical Applications

• Quadrupole GC-ICP-MS enables routine speciation at sub-ng/mL levels with simple sample preparation.
• Sector-field GC-ICP-MS offers superior sensitivity and lower detection limits, critical for compliance with stringent environmental regulations.
• Simultaneous introduction of aqueous standards with volatile species ensures robust quantification in complex matrices.

Future Trends and Potential Applications

Advances in high-resolution ICP-MS and novel GC interfaces will further lower detection thresholds for emerging contaminants. Integration of automated sample preparation and data processing will expand applications to food safety, pharmaceuticals and metabolomics. Coupling with tandem mass spectrometry may enable structural confirmation of unknown species.

Conclusion

GC-ICP-MS coupling with either quadrupole or sector-field ICP-MS provides a powerful solution for ultra-trace elemental speciation. The ELEMENT 2 configuration delivers highest sensitivity and lowest detection limits, meeting tight regulatory demands. The methodology is adaptable to diverse sample types for direct monitoring of toxic species in environmental and industrial settings.