Conventional CVG makes use of chemical reducing agents
such as sodium tetrahydroborate(III) or tin(II) chloride for the
reduction of Hg(II) to Hg(0).4 This reduction is very efficient and
can be accomplished in both batch and online systems. However,
these reducing agents are expensive and unstable (i.e., freshly
prepared reagents are required). In addition, traditional tetrahydroborate(
III)-based CVG methods are prone to interferences by
transition metals due to their interaction with the reducing reagent
or catalytic decomposition of the reaction products on the surfaces
of the reduced concomitant metals.