Mercury is one of the most toxic elements that may be found in natural water bodies and can negatively affect living organisms, human health as well as drinking water quality. In addition, water is the main transportation and transformation pathway of mercury into the environment and living organisms. Mercury analysis in water is of great importance, in order to monitor water quality and associated environmental stresses. Mercury is also known to be a persistent, bio-accumulative toxin, indicating that its toxicity does not diminish through decomposition or chemical reaction, and that it is absorbed faster than it can be excreted. Recently, efforts to minimise the release of mercury, and to track its migration when released, have demanded more sensitive analytical techniques for its measurement.