Determination of Mercury by Flow Injection-Atomic Fluorescence Spectrometry Using Chromium(II) Reduction-Cold Vapor Generation

Abstract

Chromium(II) ions were produced through the reduction of chromium(III) ions by using a flow-type electrolytic cell, and applied to the cold vapor generation of mercury in the presence of iodide. The atomic fluorescence intensity of the vaporized mercury was determined at 253.7nm on an atomic fluorescence spectrometer coupled with a flow injection device. The chromium(II) reduction system could completely reduce the mercury-iodide complex, HgI₄^2-, to elemental mercury, thus enabling an atomic fluorescence determination. The addition of iodide ions (>10mg l^-1 as the final concentration) stabilized mercury ions as HgI₄^2- and showed no memory effect due to the adsorption of mercury on the inner walls of the system. Therefore, ample iodide ions were first added to sample solutions; the formed mercury-iodide complex was then reduced to elemental mercury using an on-line chromium(II) reduction system. The present method can be used to determine mercury at the μg l^-1 level in aqueous samples without any interference from coexisting iodide ions at a level as great as 100mg l^-1.