Cold Vapor Atomic Absorption (CVAA)
Galbraith Laboratories uses Cold Vapor Atomic Absorption (CVAA) to measure mercury content of organic and non-organic samples. CVAA measures mercury content by reducing it to the elemental state and purging it from solution into an aerosol. The aerosol passes through an atomic absorption spectrophotometer where absorption of light (253.7 nm) is measured. The absorbed light correlates to the mercury content of the analysis solution.
Aqueous samples must be acidified and organic samples must be digested prior to analysis.
Mercury is reduced to the elemental state by Tin (II) Chloride. The reduced sample solution is purged with air to liberate mercury as an aerosol. The aerosol passes into an atomic absorption cell where absorbance at 253.7 nm is recorded.
Galbraith’s general method was written from the nationally accepted methods, EPA SW846 7470 and 7471. Click below to view a copy of the method summary:
Galbraith also offers analysis for mercury by ICP-MS.
Unless otherwise evaluated, the quantitation limit (QL) depends on the concentration of the lowest calibration standard used to calibrate the instrument. In general, the QL of this method is 0.012 mg/L. Results that read below the QL are reported as less than values, i.e <50 ppb.
Results are reported using the mass of sample originally taken for the analysis. Typical reporting units are ppm, ppb, mg/L, or µg/L. Other units may be reported.
CVAA is susceptible to a variety of interferences. Undigested organic matter, Sulfide and high chloride levels are the most common. These are addressed by adequately digesting the sample, treating the sample with permanganate to oxidize sulfide and hydroxylamine is added to ensure free chlorine is not present.
The general methodology is suitable for the analysis of regulated samples. The method is considered validated to a reference substance, but not to the sample matrix unless a formal validation is conducted.