What are CVAA Mercury Analyzers Systems?
In a previous blog post, we wrote about Cold Vapor Atomic Absorption Spectroscopy, a primary technique for mercury analysis. In this post, we will describe Teledyne Leeman Labs’ instruments that facilitate the process.
Leeman Labs offers two CVAA systems; the Hydra IIAA, an entry-level CVAA system that can detect mercury limits of less than 5.0 ng/L with a usable range of 5 ng/L to 1 mg/L; and the QuickTrace M-7600 CVAA Mercury Analysis System, which is a dual beam system capable of ultra-trace detection limits of less than 0.5 ng/L.
Hydra IIAA Mercury Analyzer
The Hydra IIAA design was based on the US EPA method 245.1, which allows for determination of total mercury in drinking, surface, ground, sea and brackish waters and industrial and domestic wastewaters. Method 245.1 typically requires sample digestion techniques that produce liquid samples with mercury present in the +2 valence state. The Hydra IIAA system can be converted to a direct analysis combustion mercury analyzer by quickly changing the analyzer’s module.
The system works as an acidified digested aqueous sample from an autosampler is introduced via the peristaltic pump as Hg2 dissolved in a solution of stannous chloride (10% w/v) in 10% hydrochloric acid. A sodium or potassium borohydride solution will also work. At the same time, a reducing agent (10% SnCl2 in 7 – 10% HCl) is introduced via another parallel peristaltic pump channel.
The sample and the reagent streams meet at the mixing tee and then enter the mixing tube where the stannous chloride (Sn2+) reduces Hg2+ into Hg0 while the mixture is on its way to the Gas Liquid Separator (GLS). At this stage, the analyte is present as a finely dispersed emulsion of liquid (metallic) Hg0 micro-droplets, in excess SnCl2 solution medium.
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