The determination of Hg by cold-vapor atomic absorption (CVAA) was first proposed by Poluektov et. al. in 1963. In this method mercuric ions in an acidic solution are reduced to ground state mercury atoms by a reducing agent such as stannous chloride. The mercury atoms are then swept by an inert gas stream into a quartz absorption cell placed in the optical path of an atomic absorption instrument. In the past, this produced a transient atomic absorption signal with which the analyst attempted to obtain good accuracy and precision. Through automated analysis we are able to do this.
This technique assumes that your sample is in aqueous form and all mercury in solution is unbound and present as the mercuric ion. If this is not the case, please see ASTM D3223-02: Standard test method for total mercury in water or alternate digest plans that may be available.
The Center’s Teledyne Hydra II uses the CVAA technique so that low concentration mercury, high ppt to mid ppb range, in solution can be safely measured with minimal waste generated for disposal.
This tool does have some hurdles to overcome, as do most mercury analysis systems. Common interferences:
- Interferences have been reported for waters containing sulfide, chloride, copper and tellurium.
- Organic compounds which have broad band UV absorbance (around 253.7 nm) are confirmed interferences. Contaminant (e.g. interferences) concentration levels difficult to define, so quality control procedures must be strictly followed.
- Volatile materials (e.g. chlorine) which absorb at 253.7 nm will cause a positive interference.
- Low level mercury sample preparation, digestion, and analysis may be subject to environmental contamination if performed in areas with ambient backgrounds where mercury was previously employed as an analytical reagent in analyses such as total Kjeldahl nitrogen (TKN) or chemical oxygen demand (COD).
This is another system that uses a proprietary sample vial. Part numbers and most recent cost can be obtained from CEST staff.