Analysis of Organotin Compounds in Biological and Environmental Samples by Gas Chromatography and Pulsed Flame Photometric Detection (GC-PFPD)

Importance of the topic

Organotin compounds serve as stabilizers, catalysts, biocides and pesticides across multiple industries. Despite the ban on their use in marine antifouling paints since 2008, they persist in water, sediment and biota, posing endocrine disruption risks. The high toxicity and bioaccumulation potential of organotins drive regulatory control and growing demand for robust analytical methods in environmental and biological monitoring.

Study objectives and overview

This study aimed to develop a sensitive, selective and accessible gas chromatography–pulsed flame photometric detection (GC-PFPD) method for organotin analysis. Key goals included establishing a reliable derivatization protocol, optimizing instrument parameters for tin specificity, generating calibration data, and demonstrating application in wastewater, sludge, urine and blood samples.

Methodology

Derivatization of tin chlorides and sample extracts was achieved via ethylation with sodium tetraethylborate (STEB) in THF or methanol and sodium acetate buffer at pH 4.9. Careful handling of pyrophoric STEB under inert gas was essential. Multi-point calibrations were performed and linear regression applied. Samples were processed at three laboratories (San Diego PUD, OI Analytical and University of Iowa) to assess reproducibility and detector contamination issues.

Instrumentation

The method employed Shimadzu GC-2010 Plus and Agilent 7890A gas chromatographs coupled to OI Analytical PFPD models 5380 and 5383. Columns included Restek Rtx-1, Rtx-5, Rxi-5MS, Rxi-35SIL MS and Supelco SPB-1 (30 m×0.25 mm, film thickness 0.25–1.0 μm). Detector temperatures of 325–350 °C reduced peak tailing. Typical hydrogen and air flows ranged from 11–13 mL/min. Splitless injections (1–2 μL) were used with temperature programs tailored to each lab’s matrix.

Main results and discussion

Calibration covered 0.5–250 ppb with correlation coefficients ≥0.997 for monobutyltin, dibutyltin, tributyltin and tetraethyltin. Raising PFPD temperature above 325 °C minimized peak tailing. Wastewater and sludge extracts showed no detectable MBT, DBT or TBT, while human urine contained 0.6 ppb MBT and 3.7 ppb DBT; blood analyses required alumina clean-up. Matrix effects were mitigated by adjusting extract concentration, column selection and oven programming. Detector contamination at ~3–4.5 ms was linked to prolonged high-level injections; resolving strategies included clipping the column end and installing a guard column.

Benefits and practical applications

• The GC-PFPD approach provides part-per-billion sensitivity and high tin selectivity over hydrocarbons.
• Derivatization and instrument setup utilize common laboratory glassware and resources.
• Applicable to diverse matrices—environmental waters, sludge, biological fluids—without specialized capital investment.

Future trends and potential applications

As regulatory scrutiny intensifies, wider adoption of GC-PFPD for organotin monitoring is anticipated. Future refinements may include enhanced sample clean-up techniques, guard column deployment to extend column life, alternative derivatization reagents, and automated workflows. Expanding to other organometallic analytes and miniaturized detector designs may further improve throughput and field applicability.

Conclusion

The presented GC-PFPD method offers a reliable, rugged and cost-effective solution for organotin analysis in environmental and biological samples. With straightforward derivatization, optimized detector conditions and robust calibration, laboratories can implement this protocol to meet increasing demands for organotin monitoring.

Reference

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