Determination of Chemical Cpecies and Canoparticles in Water Samples: Analytical Methods, Preconcentration and Validation
It is now recognized that measurement of the total concentration of an element is not sufficient to obtain information about its environmental impact and its toxicity, elements being present under different chemical forms or as nanoparticles (NPs). Only size fractionation techniques or speciation analysis (identification and determination of the different species of an element) yield this information. This approach needs to have well defined sampling, storage and sample treatment procedures that do not modify the distribution of the chemical forms. Furthermore, taking into account the new EU regulations, this approach also needs more and more sensitive, accurate and robust analytical tools. Hyphenation between separation techniques based on liquid or gas chromatography or flow fractionation on one hand and inductively coupled plasma mass spectrometry (ICP MS) on the other hand are analytical methods that present the greatest potential for these analyses. An overview of these approaches is detailed in terms of their potential and their analytical performances as well as applications for different elements (As, Hg, Sn, Cr or Sb). Through these examples, the following items will be described : The main validation tools such as species isotopic dilution (methylmercury in natural waters) and the use of alternative methods (example of Sb speciation); Preconcentration techniques to decrease quantification limits to be in agreement with new regulations (Cr(VI)); The physico-chemical characterization of colloïds in natural waters.