Stability and storage problems in organotin speciation in environmental samples

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.

Long-term stability and temporal trends of organic contaminants in four collections of mussel tissue frozen standard reference materials

The stability of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and chlorinated pesticides in frozen mussel tissue Standard Reference Materials (SRMs) stored at -80 °C was assessed by analyzing samples of SRM 1974, SRM 1974a, and SRM 1974b Organics in Mussel Tissue (Mytilus edulis) periodically over 25 y, 20 y, and 12 y, respectively. The most recent analyses were performed during the certification of the fourth release of this material, SRM 1974c. Results indicate the concentrations of these persistent organic pollutants have not changed during storage at -80 °C. In addition, brominated diphenyl ethers (BDEs) were quantified in each of the materials during this study. The stability information is important for on-going monitoring studies collecting large quantities of samples for future analyses (i.e., formally established specimen banking programs). Since all four mussel tissue SRMs were prepared from mussels collected at the same site in Dorchester Bay, MA, USA, the results provide a temporal trend study for these contaminants over a 17 year period (1987 to 2004).

Storage stability studies for tributyltin determination in human urine samples using headspace solid-phase microextraction and gas chromatography mass spectrometry

A headspace solid-phase micro-extraction (HS-SPME) method was employed in order to study the effect of storage conditions of human urine samples spiked with tributyltin (TBT) using gas chromatography and mass spectrometry. To render the analyte more volatile, the derivatization (ethylation) was made in situ by sodium tetraethylborate (NaBEt(4) ), which was added directly to dilute unpreserved urine samples and in buffers of similar acidity. The stability of TBT in human urine matrix was compared with the stability of TBT in buffer solutions of similar pH value. Critical parameters of storage conditions such as temperature and time, which affect the stability of TBT in this kind of matrix, were examined extensively. The tests showed that the stability of TBT remains practically satisfactory for a maximum of 2 days of storage either at +4 or 20°C. Greater variations were observed in the concentration of TBT in human urine samples at +4°C and lower ones at -20°C over a month's storage. The freeze-thaw cycles have negative effect on the stability and should be kept to a minimum. The results from spiked urine samples are also discussed in comparison to those acquired from buffer solutions of equal TBT concentration.

Speciation and degradation of triphenyltin in typical paddy fields and its uptake into rice plants

Triphenyltin (TPhT) is a biocide used worldwide in agriculture, especially in rice crop farming. The distribution and dissipation of TPhT in rice fields, as well as uptake of TPhT and other phenyltin compounds (monophenyltin, MPhT, and diphenyltin, DPhT) is still unknown at present. In this study, speciation analysis of phenyltin compounds was carried out in soil and water from a rice field where TPhT was applied during rice seeding according to legal application rates in Brazil. The results indicate the degradation of biocide and distribution of tin species into soil and water. To evaluate whether TPhT is taken up by plants, rice plants were exposed to three different TPhT application rates in a controlled mesocosm during 7 weeks. After this period, tin speciation was determined in soil, roots, leaves, and grains of rice. Degradation of TPhT was observed in soil, where DPhT and MPhT were detected. MPhT, DPhT, and TPhT were also detected in the roots of plants exposed to all TPhT application rates. Only TPhT was detected in leaves and at relatively low concentration, suggesting selective transport of TPhT in the xylem, in contrast to DPhT and MPhT. Concentration of phenyltin species in rice grains was lower than the limit of detection, suggesting that rice plants do not have the capability to take up TPhT from soil and transport it to the grains.

Zebrafish larvae as a model for the evaluation of inorganic arsenic and tributyltin bioconcentration

The European REACH legislation establishes the need to study the toxicity, persistence and bioaccumulation of those chemicals with an exceeding production of 100tons and/or chemicals considered PBTs substances (Persistence, Bioaccumulation and Toxicity). Currently, the OECD technical guideline 305 is the most used protocol to determine bioconcentration factors of contaminants in aquatic environments. However, this procedure implies high cost and amount of adult fishes. Zebrafish (Danio Rerio) has been selected since this animal model has several advantageous features over other vertebrates, mainly fast embryonic development and easy growth. The analytical methodology here developed has been applied to calculate the bioconcentration factors (BCFs) of two contaminants: inorganic arsenic and tributyltin (measured as arsenic and tin). The method is based on the use of an ultrasonic probe assisted extraction for accelerating the sample treatment followed by detection using graphite furnace atomic absorption spectrometry with Zeeman correction (ZGFAAS). Results obtained for the BCFs values are in good agreement with previously reported data on freshwater aquatic organisms. In the case of arsenic, after exposing larvae to concentrations of 5 and 50μgL(-1), very low BCFs were observed (between 2.2 and 9.5); while for tributyltin, the BCFs observed were within the range 840-1280 after exposure to concentrations of 0.2 and 2.0μgL(-1), respectively. This study shows the use of zebrafish larvae together with the proposed analytical approach as a promising alternative to the OECD 305 test to evaluate the BCFs of classical and emergent contaminants.

Preparation, preservation and application of pure isotope-enriched phenyltin species

A method combining liquid/liquid extraction and chromatographic fractionation has been developed for the preparation of pure monophenyltin (MPhT), diphenyltin (DPhT), and triphenyltin (TPhT), synthesized from isotope-enriched Sn metal using phenylation of SnI(4) in diethylether (DEE) followed by quenching with HBr and water. After two successive extractions of the aqueous HBr phase with DEE, >99% of both DPhT and TPhT was recovered in the combined DEE phase and 94% of the MPhT remained in the aqueous phase. The MPhT in the aqueous phase was extracted into dichloromethane. The organic phases were vaporized and the PhTs were redissolved in MeOH/water/acetic acid/sodium acetate (59/30/6/8, v/v/v/w), which was also used as storing solution. Aliquots of the two solutions containing either DPhT and TPhT or MPhT were injected into a silica-based C(18) column for isolating and purifying single species. The yields of pure MPhT, DPhT, and TPhT, each synthesized from isotope-enriched (118)Sn metal, (122)Sn metal, and (124)Sn metal, were better than 99%. After chromatographic separation, the single phenyltin compounds were mixed to prepare a spike for multiple-isotope species-specific isotope dilution (MI-SSID). MI-SSID was successfully used to determine phenyltin compounds in the certified reference material, mussel tissue BCR CRM-477. At -20 degrees C, all of the fractionated phenyltin species were stable in the storage solution for at least 197 days. When these standards were stored at 4 degrees C or 22 degrees C, 4-6% of the DPhT and TPhT degraded within 27 days. The degradation of DPhT and TPhT increased with the ionic strength and acidity of the storage solution.

Organotin contamination in the Atlantic Ocean off the Iberian Peninsula in relation to shipping

Imposex in female snails, a bioindicator of TBT contamination, and the presence of organotins in snails' tissue and sediments were studied at nine sites off the western Iberian Peninsula. The study was part of a European project (acronym HIC-TBT) co-financed by the EU-LIFE programme, intending to investigate and communicate the impact of organotins from ships in marine ecosystems. Snails and sediments were sampled during two cruises in May/June 1999 and in January 2000 in areas of high, intermediate and low-shipping density. Imposex was found in female snails from several sampling sites, some of which had an imposex incidence of 100%. Differences in sensitivity were found between species; hence comparison of imposex levels between locations where different species were collected was not straightforward. Total organotin concentrations in sediments (sum of butyl and phenyltin compounds) ranged from 21 to 185 ng Sn g(-1) with higher values for most sites sampled in the vicinity of shipping lanes. Organotin concentration in snails' tissue ranged from <5 to 196 ng Sn g(-1), which are similar to those found in snails from other offshore areas contaminated by TBT. Overall, these results give further support to the recent ban on the use of organotin based antifouling paints to all ship size.

Concentrations of organotin compounds and imposex in the gastropod Hexaplex trunculus from the Lagoon of Venice

In four stations located close to the channels connecting the Lagoon of Venice with the Adriatic Sea (two inside the lagoon and two outside it), individuals of Hexaplex trunculus were collected in order to assess their contamination. Concentrations of some organotin compounds, i.e. tributyltin and triphenyltin with their di- and mono- substituted metabolites, were measured and endocrine disruption such as imposex (superimposition of male sexual characteristics on females of gonochoristic gastropods) was observed. Vas deferens sequence indexes (VDSI) of 4.1-4.9 were found in organisms from stations inside the lagoon, and 3.6-4.2 in the sea stations. Organotin derivatives were measured in both the visceral coil and the rest of the soft body of the organisms. Total concentrations of butyltin compounds ranged from 102 +/- 17 to 432 +/- 27 ng Sn g(-1) d.w. in the visceral coil, and from 96 +/- 24 to 297 +/- 107 ng Sn g(-1) d.w. in the rest of the soft body. Phenyltins were found at far lower concentrations, ranging from 8 +/- 1 to 41 +/- 3 ng Sn g(-1) d.w. (visceral coil) and from 0.25 to 32 +/- 22 ng Sn g(-1) d.w. (rest of soft body). The degree of imposex in female gastropods, evaluated from VDSI and penis lengths, was related to organotin contents in the soft body. In particular, female penis lengths were significantly correlated (r = 0.917 and r = 0.982, P<0.05) to tributyltin (TBT) contents and the sum of organotin compounds in organisms.

Temporal fluctuations of tributyltin in the bivalve Venerupis decussata at five stations in southwest Spain

Filter feeding clams, Venerupis decussata, were sampled every 4 months for 8 years at five locations on the southwest Spain coast and analysed for organotins. All the stations showed a significant sinusoidally shaped seasonal evolution pattern for tributyltin (TBT) superimposed upon a linear decreasing tendency. The amplitude and frequency of fluctuations differed among stations and were correlated to the harbour activities. Fluctuations were greatest at stations with the greatest TBT presence. The long-term trend of TBT in clams indicated half-life values of about 7-14 years. During 1993, water and sediment samples were also collected at monthly intervals and analysed. Correlations between TBT bivalve contents and water concentrations were higher than those found between biota and sediments.