Leeman Labs PS200II Mercury Analyzer - Theory
The PS200 II employs a spectrometric absorbance technique for the determination of the concentration of mercury in a liquid sample. Unlike other analytical techniques, the initial oxidation state of the mercury in the sample is not important.
Using a peristaltic pump, a portion of the sample is combined with an acidic tin chloride solution. The tin chloride reduces all of the mercury species to ground state mercury. After a short delay, to allow the reduction reaction to take place, the ground state mercury is stripped out of the sample using an argon stream.
The stripping gas is passed from the reaction area into an absorbance cell. Light from an argon source is passed down the axis of the absorbance cell, and into a photocell on the other end of the cell. Any mercury vapor entering the cell absorbs some of the light emitted from the source. The amount of light absorbed by the mercy vapor is proportional to the amount of mercury present in the cell. The concentration-absorbance relationship is defined by analyzing a set of standards. The mercury concentration in an unknown sample is then determined by comparing the observed absorbance with the relationship determined from the standards.