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Researchers have developed a method to quantify concentrations of the pollutant tributyltin (TBT) in whole water bodies using species-specific isotope dilution (SSID) and gas chromatography with inductively coupled plasma mass spectrometry (GC–ICP-MS).
Researchers have developed a method to quantify concentrations of the pollutant tributyltin (TBT) in whole water bodies using species-specific isotope dilution (SSID) and gas chromatography with inductively coupled plasma mass spectrometry (GC–ICP-MS) (1).
The implementation of the European Water Framework Directives (WFD) placed new and challenging demands on the analytical methods used for environmental water analysis. The reassessed list of toxic substances also came with new environmental quality standards (EQS) and limits of quantification (LOQ), and for several substances these defined limits were below the LOQ of established analytical methods (2,3).
A key point in the new WFD directives instructed the analysis of whole water bodies removing the filtration step usually associated with the analysis of surface waters. In practice this dictates that both dissolved contaminants and contaminants associated with suspended solids and colloids must be quantified, adding further caveats to the method development process.
TBT was highlighted as a priority because of the low EQS set by the WFD, stemming from its high toxicity in the aquatic environment (2,4) and the lack of a standardized analytical method. Disorders in growth, development, and reproduction in marine species have all been attributed to TBT contamination (5), and studies have also found TBT responsible for endocrine system imbalances in mammals, specifically humans and rodents (6).
While effective regulations have led to reduced TBT contamination, the pollutant will still be present in water, sludge, and soil for an indefinable time because of its high adsorption affinity to organic matter (7). Furthermore, natural sinks formed in sediments are continuously releasing TBT into aquatic ecosystems, which is expected to continue for decades (8).
In order to meet all of the WFD requirements, researchers developed two methods. Both used elaborate sample preparation and sample treatment in combination with a sensitive analytical technique (GC–ICP-MS) and quantification by isotope dilution to monitor TBT at sub ng/L-1 in complex waters with a wide range of humic acids (HA) and suspended particulate matters (SPM).
The designed methods showed high recoveries at defined levels of HA and SPM contents, however, when real surface waters were investigated it was shown that the developed method with a filtration step determined higher concentrations of TBT compared to the method that neglected the TBT adsorption at SPM and HA. Spiking experiments showed good robustness in the method.
The presented methods met the challenging criteria set by the WFD for monitoring TBT in surface waters and the authors also believe the described procedure could be applicable to TBT transformation products and other organotin species. - L.B.