Chemical Stability and Compatibility - Mercury (Hg) stability in plastic containers

The amount of time before instability may be observed appears to be a function of concentration, in that concentrations of <100 ppb (approximately) Hg preserved in HNO3 and stored in plastic may be ‘lost’ within minutes to hours. Higher concentrations of ~10-100 ppm may suffer a few ppm of Hg loss over weeks to months. Our general supposition is that the total amount of Hg that may be adsorbed is a function of the availability of reactive sites on plastic surfaces, and therefore could be related to ratio of volume to surface area. It also appears that how the bottle is cleaned beforehand could affect Hg stability. It seems that with regard to Hg stability in HNO3 and plastic bottles that simple answers are difficult to come by. For your application, we would predict that ~100 ppb or lower Hg solutions in 2-5% (v/v) HNO3 that are stabilized with 1 ppm Au (as Au-chloride) would be stable for weeks to months (we would not expect any issues over a few days). As for the NaCl solution, the total amount of chloride present may likely affect Hg stability, as HCl matrices (>5%) are effective at stabilizing Hg in plastic containers, and you are in essence creating a pseudo-HCl matrix by combing NaCl with HNO3. A working hypothesis would be that if the NaCl/Hg ratio is high enough, and the solution sufficiently acidic, then Hg would be stable for more than a few days. However, as you can imagine, there are a large number of important variables, and we think your approach of conducting stability studies of your specific solutions is an excellent idea.