TM92-03 Mercuric Chloride Preservation of S-34/S-32, O-18/O-16, and H-2/1-1-1 Samples

At present, the National Water Quality Laboratory (NWQL) catalog states that mercuric chloride should be added to samples for the stable isotope analyses for sulfur, oxygen, and deuterium ratios. Both the Chief of the Reston Isotope Lab and the Chief of the Denver Sulfur Isotope Lab have asked that this HgCl2 requirement be deleted. They agree that the HgCl2 is not necessary; that omitting the HgCl2 would improve conditions for the analysts, and that this would prevent unnecessary pollution of the environment. The NWQL conducted a comparison study to determine if the HgCl2 affected the results of these analyses (attached). As can be seen from the comparison data, the results are unaffected by the HgCl2. Please discontinue the addition of HgCl2 to samples for the stable isotope analyses for sulfur, 
oxygen, and deuterium. This policy is effective as of the date of this memorandum.