Cold-vapor mercury atomic absorption spectrometry: HCl as the cause of the double peak phenomenon.

An investigation has been made on the intermittent second peak that occurs in cold-vapor mercury atomic absorption spectrometry. Evidence that this peak is due to hydrogen chloride gas is presented. Analytical determination of mercury should therefore not include this peak, and a means to suppress or eliminate it, using glass wool adsorption between the reaction vessel and the spectrometer, is suggested.