Infrared radiation-assisted thermochemical vapor generation for mercury speciation by atomic absorption spectrometry†

Abstract

A simple, low-cost and sensitive technique using infrared radiation for thermochemical vapor generation coupled with atomic spectrometry was developed for the determination of mercury species in biological matrices. Thermochemical vapor generation (TVG) of inorganic and methylmercury species can be achieved by heating samples of formic acid solubilized materials with and without the use of hydrogen peroxide, respectively, at temperatures of 165 to 285 °C. Power output from a 1000 W infrared lamp was regulated via temperature-controlled output measured with a thermocouple. A quartz tube was used to flow the sample through the TVG reactor. The impacts of formic acid and hydrogen peroxide concentration, temperature and carrier gas flow (N₂) were evaluated in the system on response from inorganic and methylmercury in order to identify optimal conditions for thermochemical vapor generation efficiency. The accuracy of the method was validated using Certified Reference Materials NIST 1641d and NRC DORM-1 and DOLT-3.