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- Tributyltin (TBT) (1)
The European Union (EU) has included tributyltin (TBT) and its compounds in the list of priority water pollutants. Quality standards demanded by the EU Water Framework Directive (WFD) require determination of TBT at so low concentration level that chemical analysis is still difficult and further research is needed to improve the sensitivity, the accuracy and the precision of existing methodologies. Within the frame of a joint research project “Traceable measurements for monitoring critical pollutants under the European Water Framework Directive” in the European Metrology Research Programme (EMRP), four metrological and designated institutes have developed a primary method to quantify TBT in natural water using liquid–liquid extraction (LLE) and species-specific isotope dilution mass spectrometry (SSIDMS). The procedure has been validated at the Environmental Quality Standard (EQS) level (0.2 ng L−1 as cation) and at the WFD-required limit of quantification (LOQ) (0.06 ng L−1 as cation). The LOQ of the methodology was 0.06 ng L−1 and the average measurement uncertainty at the LOQ was 36%, which agreed with WFD requirements. The analytical difficulties of the method, namely the presence of TBT in blanks and the sources of measurement uncertainties, as well as the interlaboratory comparison results are discussed in detail.
Determination of tributyltin in whole water matrices under the European water framework directive
(2016)
Monitoring of water quality is important to control water pollution. Contamination of the aquatic systemhas a large effect on human health and the environment. Under the European Water Framework Directive(WFD) 2000/60/EC and the related directive on environmental quality standards (EQS) in the field of waterpolicy 2008/105/EC, the need for sensitive reference methods was highlighted. Since tributyltin (TBT) isone of the WFD listed priority substances a method was developed which is capable to qualify and quantifythe pollutant at the required low WFD EQS of 0.2 ng L⁻¹ in whole water bodies, i.e. in non-filtered watersamples with dissolved organic carbon and suspended particulate matter. Therefore special attention waspaid on the interaction of TBT with the suspended particulate matter and humic substances to obtain acomplete representation of the pollution in surface waters. Different water samples were investigatedvarying the content of organic dissolved and suspended matter. Quantification was performed usingspecies-specific isotope dilution (SSID) and gas chromatography with inductively coupled plasma massspectrometry (GC-ICP-MS). Different sample treatment strategies were evaluated and compared. Theprocess of internal standard addition was investigated and optimized, hence the equilibrium betweeninternal standards and matrix is of primary importance to perform accurate SSID. Samples spiked at EQSlevel were analyzed with a recovery between 95 and 105 %. Additionally real surface water samples wereinvestigated and the TBT concentration for the whole water body was determined and compared withconventional routine analysis method.
The European Water Framework Directive 2000/60/EC requires monitoring of organic priority pollutants in so-called whole water samples, i.e. in aqueous nonfiltered samples that contain natural colloidal and suspended particulate matter. Colloids and suspended particles in the liquid phase constitute a challenge for sample homogeneity and stability. Within the joint research project ENV08 ‘‘Traceable measurements for monitoring critical pollutants under the European Water Framework Directive 2000/60/EC’’, whole water test materials were developed by spiking defined amounts of aqueous slurries of ultrafinely milled contaminated soil or sediment and aqueous solutions of humic acid into a natural mineral water matrix. This paper presents the results of an European-wide interlaboratory comparison (ILC) using this type of test materials. Target analytes were tributyltin, polybrominated diphenyl ethers and polycyclic aromatic hydrocarbons in the ng/L concentration range. Results of the ILC indicate that the produced materials are sufficiently homogeneous and stable to serve as samples for, e.g. proficiency testing or method validation. To our knowledge, this is the first time that ready-to-use water materials with a defined amount of suspended particulate and colloidal matter have been applied as test samples in an interlaboratory exercise. These samples meet the requirements of the European Water Framework Directive. Previous proficiency testing schemes mainly employed filtered water samples fortified with a spike of the target analyte in a water-miscible organic solvent.
We have prepared and evaluated three whole water test materials containing eight polycyclic aromatic hydrocarbons (PAHs), six polybrominated diphenyl ethers (PBDEs) and tributyltin (TBT) with respect to homogeneity and short-term stability. The test materials were used as samples in two inter-laboratory comparisons. The materials were composed of natural mineral water and model suspended particulate matter (SPM) containing the target compounds at ng L-1 levels. The expanded uncertainty of the estimated mass concentrations in the final test materials was obtained by combining contributions from the homogeneity, the stability and the model SPM characterization.
The whole water materials were sufficiently homogeneous and stable at 4 °C for their intended use. In total, 12 out of 15 investigated target parameters could be assessed to be present with a relative combined expanded uncertainty below 25 %. The outcome of the two interlaboratory comparisons confirmed the good quality of the test materials and the level of uncertainties associated with the estimated mass concentrations. These findings are an important contribution towards the development of whole water matrix reference materials certified for PAH, PBDE and TBT in support of the Water Framework Directive of the European Union.