Use of gold as a routine and long term preservative for mercury in potable water, as determined by ICP-MS

A study was made of the effects of storing both deionised and potable water spiked with mercury in both glass and poly(ethylene terephthalate) (PET) containers, using gold as a preservative. Bulk solutions of mercury at three different concentrations ( 0.5, 1.0 and 1.5 mu g l(-1)) were prepared separately in deionised (DI) water and locally obtained potable water. Individual glass and PET bottles containing gold, as gold chloride solution, were filled with these solutions and then analysed over a four week period, by ICP-MS. Details of the ICP-MS operational criteria are given in the text. The results show that there was little difference in mercury recovery from any of the solutions used when stored in either the glass or the PET containers during the study. The maximum/minimum recoveries for each system spiked at 1 mu g l(-1) Hg were: glass-DI water 103/93%; glass-potable water, 106/96%; PET + gold-DI water, 103/97%; PET + gold-potable water, 106/99%. This establishes the effectiveness of gold as a preservative agent for mercury in potable water up to a concentration of 1.0 mu g l(-1) Hg, adequately covering the range up to the Prescribed Concentration or Value (PCV) required by UK legislation. The effect of the gold on the analysis of other low concentration metals in potable water using ICP-MS was studied and recoveries ranging from 92-103% were obtained in its presence. The determination of mercury using the cold vapour fluorescence technique was affected by the presence of the gold chloride. All mercury containing solutions and standards were matrix matched to potable water by the addition of calcium, potassium and sodium salts.