I found out that the best way for digesting samples for Hg analysis is a closed microwave digestion with HNO3 and some HCl. No Hg will be lost. What if i am doing a multi element analysis?
Total mercury analysis in water does not provide enough information about the quality of the water as regards this element. The studies of mercury may involve the analysis of bivalve species, which accumulate metals, sediment and water. These may provide an estimation of the level of pollution in a water system. There are many articles reporting validated methods for the analysis of the mercury species in aquatic systems.
You'd better study the" Handbook of Elemental Speciation II – Species in the Environment, Food, Medicine and Occupational Health". This book gives you sufficient information about this issue.
For mercury analysis , digestion must be done below 90oC due to loss of mercury at higher temperatures. Unfortunately this is a partial digestion procedure and microwave may be used, but you need to control the temperature effectively. Another is an ultrasonic method, which is fast and effective. Analysis of mercury is done by vapour generation. I hope this helps