A Comparison of GC-ICP-MS and HPLC-ICP-MS for the Analysis of Organotin Compounds

Importance of the topic

Organotin compounds are persistent environmental pollutants with well-documented toxic effects in aquatic and human matrices. Their widespread use in antifouling agents, PVC stabilization, and industrial products has led to their accumulation in marine sediments, seafood, drinking water infrastructure, and even in blood. Accurate trace-level speciation analysis is critical to assess environmental exposure and human health risks, demanding methods combining selectivity, sensitivity, and robust quantification.

Study objectives and overview

This study presents a comparative evaluation of gas chromatography coupled to inductively coupled plasma mass spectrometry (GC-ICP-MS) and high-performance liquid chromatography coupled to ICP-MS (HPLC-ICP-MS) for the determination of organotin species. The objectives include assessing chromatographic performance, detection limits, method precision, and accuracy in complex matrices, using isotope dilution mass spectrometry (IDMS) to minimize uncertainties.

Methodology

An accelerated solvent extraction protocol was applied to sediment samples using a sodium acetate/acetic acid/methanol mixture, followed by dilution for HPLC analysis and derivatization with sodium tetraethylborate for GC analysis. Both techniques employed IDMS calibration, mixing isotopically enriched 117Sn-tributyltin spike with standards and samples. Chromatographic separations were optimized to resolve six compounds by HPLC and over ten by GC in a single run.

Instrumentation

• HPLC: Agilent 1100 system with PEEK components and a C18 column (2.1×150 mm, 3 μm).
• GC: Agilent 6890 GC equipped with an Agilent G3158A interface for ICP-MS coupling.
• ICP-MS: Agilent 7500i with ShieldTorch and secondary pump, optimized for low oxide and doubly charged ion formation.
• Detector tuning: Peltier-cooled spray chamber (−5 °C), oxygen or nitrogen addition to the carrier gas to enhance organic plasma stability and signal.

Results and discussion

GC-ICP-MS separated 10–12 organotin species per run versus 5–6 for HPLC-ICP-MS. HPLC afforded 40 % shorter cycle times and eliminated derivatization steps, while GC provided sharper peaks (4–6 s vs. 50–60 s) and greater baseline stability. Sensitivity enhancements by adding 5 % O2 or N2 to the plasma gas increased response factors up to 150-fold, lowering detection limits for TBT from 0.4 ng mL−1 (no gas) to 0.006 ng mL−1 (5 % N2). Both methods showed comparable precision (~1.6–1.7 %) and recovered TBT from sediment at ~840 ng g−1, aligning with certified reference values.

Benefits and practical applications

• HPLC-ICP-MS: rapid, no-derivatization workflow suitable for high-throughput monitoring.
• GC-ICP-MS: superior sensitivity and broader speciation capacity for ultratrace environmental studies.
• IDMS calibration: reduces measurement uncertainty, ensures high accuracy and precision.

Future trends and possibilities

Ongoing developments may include multi-element speciation of volatile forms, integration of online extraction and preconcentration, automation of derivatization, novel stationary phases for enhanced resolution, and portable ICP-MS interfaces for field analysis. Advances in isotopic labelling and detection technologies will further improve quantification at sub-picogram levels.

Conclusion

Both GC-ICP-MS and HPLC-ICP-MS coupled with IDMS offer robust solutions for organotin speciation. Method selection hinges on the balance between throughput and sensitivity: HPLC for routine, cost-effective screening, and GC for comprehensive ultratrace analysis. The incorporation of auxiliary gases and optimized plasma conditions markedly enhances detection capabilities.

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