Examination of the different procedural steps in the determination of organotin compounds in water samples

Levels of tin and organotin compounds in human urine samples from Iowa, United States

Exposure to tin in the general US population is near ubiquitous, as determined using urinary tin levels measured by inductively coupled plasma mass spectrometry (ICP-MS). Urinary tin levels are associated with chronic health outcomes, such as diabetes; however, it is unclear if these associations are due to the presence of inorganic and organic forms of tin in urine. To address this knowledge gap, levels of total tin and several organotin compounds (OTCs) were measured in convenience urine samples from pregnant women and adults from Iowa, United States. Total tin and OTC levels in urine samples were quantified using ICP-MS and gas chromatography with pulsed flame photometric detection (GC-PFPD), respectively. ICP-MS detected tin in almost all urine samples from both study populations. Low levels of dibutyltin were detected in two out of fifty human urine samples. Importantly, storage of urine samples in plastic containers, but not HNO3-pretreated glass vials drastically reduced the recoveries of OTCs, in particular, tributyltin. Although their detection frequency is low, exposures to OTC should be considered when studying associations between human exposures to tin compounds and adverse health outcomes; however, urinary OTC levels measured in banked urine samples may not be suitable as biomarkers of OTC exposure.

Study of the degradation of butyltin compounds in surface water samples under different storage conditions using multiple isotope tracers and GC-MS/MS

The degradation of butyltin compounds in surface water samples under different storage conditions has been studied. A triple spike solution, containing monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) labelled with a different tin isotope, was added to the sample to calculate the extent of the interconversion reactions among butyltin compounds. Real surface water samples (river water) were collected and stored in glass, polypropylene or polytetrafluoroethylene (PTFE) containers. The presence of light, addition of acetic acid, storage temperature (22, 4 or -18 °C), and the influence of a filtration step were evaluated. Moreover, Milli-Q water with and without the addition of a high concentration of humic acids was prepared in parallel and the results compared to those obtained from the real samples. The water samples were analysed by gas chromatography-tandem mass spectrometry (GC-MS/MS) in selected reaction monitoring (SRM) mode at two different storage times (2 weeks and 4 months after its preparation) to carry out both a short- and a long-term stability study. The lowest butyltin degradation was obtained when the samples were stored at -18 °C in the dark. Under these conditions, both TBT and DBT showed negligible dealkylation factors after 2 weeks. After 4 months, DBT dealkylation to MBT increased up to 19 % but TBT degradation was not observed.

Rapid determination of butyltin species in water samples by multicapillary gas chromatography with atomic emission detection following headspace solid-phase microextraction

A procedure for the rapid determination of mono-, di- and tributyltin in water samples is described. The analytes are simultaneously ethylated and concentrated on a solid-phase microextraction fibre placed in the headspace over the sample for 2 min. The ethylated species are then separated and selectively quantified in only 90 s using a multicapillary gas chromatography column combined with atomic emission detection. The influence of blank signals and sampling conditions on the sensitivity of the method is described. Detection limits of 1-5 ng/l and relative standard deviations of 6-10% at concentrations of 20 ng/l were obtained.