University of Colorado at Denver and Health Sciences CenterCollege of Liberal Arts and SciencesUniversity of Colorado at Denver and Health Sciences Center
Leeman Labs PS200II Mercury Analyzer
Overview -
As the name suggests, the Leeman Labs PS200II Mercury Analyzer is used to determine the concentration of mercury in liquid sample.
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.
An overview of the PS200 II Mercury Analyzer
Methods -
Microwave digestion of media
Microwave digestion of filter paper
Detection Limits -
The Detection Limit for the PS200 II is in the low parts-per-trillion range. With other analytical techniques, this might be problematic, as samples with higher mercury concentrations would need to be diluted to bring the analyte into the concentration range corresponding to a linear absorbance response. With the PS200 II, though, the amount of sample analyzed can be decreased, and/or the flow rate of the stripping gas can increased, decreasing the amount of ground state mercury ending up in the absorbance cell. This procedure allows mercury concentrations into the parts-per-million to be determined.
Sample Matrix -
The sample must be in a liquid matrix, prefferably aqueous.
Sample Size -
Typically, 2-3 mL of sample is required for each replicate analysis.
Approximate C0st -
Neglecting the cost of sample preparation, the cost of the instrument is $XX.XX/hour.