Determination of mercury in potable water by ICP-MS using gold as a stabilising agent

A method for the routine determination of mercury in potable water samples was developed that uses addition of gold to samples to preserve mercury by amalgamation and subsequent analysis by inductively coupled plasma mass spectrometry (ICP-MS). The method was validated using the guidelines of the NS 30 document and shows compliance with the analytical performance criteria required by the UK's Drinking Water Inspectorate over the range 0-1.2 mu g l(-1) Hg. The prescribed concentration or value (PCV) for mercury is 1.0 mu g l(-1). A limit of detection 0.032 mu g l(-1) and a recovery of 99.0% at the PCV were obtained. Gold was added off-line to both samples and standard solutions. It was also added to the ICP-MS wash water to eliminate any memory effects from mercury in previous samples. The details of gold addition and the operating conditions of the Perkin-Elmer SCIEX Elan 6000 ICP-MS instrument are described. This work forms part of a project to enable the routine determination of all the low-concentration metals in potable water samples to be achieved in a single run using ICP-MS.