Comment submitted by Lisa Touet, Massachusetts Department of Environmental Protection (MassDEP)

The proposed rule permits use of ICP/AES and ICP/MS for the analysis of mercury. Historically these methods have not demonstrated very good performance for mercury. In particular, the digestions associated with the methods result in a loss of mercury. Footnote 4 of the rule requires sample digestion. Notes included in the analytical methods specify that the digestions included in the methods are not appropriate for the analysis of mercury. If it is EPAs intent to permit use of these instruments to analyze for mercury the rule must provide specific guidance as to how mercury samples should be digested and analyzed to ensure method detection limits are low enough and that loss of mercury does not occur during sample preparation.