Total Mercury Determination in Biological and Environmental Standard Samples by Gold Amalgamation Followed by Cold Vapor Atomic Absorption Spectrometry

Abstract

As a result of industrialization and changes in the environment during the twentieth century, human and animals are exposed to numerous chemical forms of mercury, including elemental mercury vapor (Hg 0), inorganic mercurous (Hg +) and mercuric (Hg 2+) compounds, and organic mercuric ( R–Hg +or R–Hg– R, where Rrepresents any organic ligand) compounds. All forms of mercury have toxic effects, therefore, it is important to determine total mercury in biological and environmental samples to establish baseline levels. This paper highlights the methodology developed for total mercury determination in biological and environmental samples using preconcentration by mercury amalgamation accessory followed by cold vapor atomic absorption spectrometry. The high-pressure microwave digested mercury samples were chemically reduced by stannous chloride and the vapor generated was collected on a mercury amalgamation tube (MAT). The concentrated mercury was revolatilized by rapid heating of the MAT to 500–800°C and was transferred to the absorption cell for determination by cold vapor atomic absorption spectrometry. The preconcentration on the MAT and subsequent revolatilization methodology was compared with the cold vapor atomic absorption determination without the preconcentration step. The preconcentration proved to be sensitive and as the result of the high sensitivity, small sample volumes were analyzed and only short sampling times were required. The values for NIST certified human urine, apple leaves, rice flour, bovine liver, buffalo sediments, estuarine sediments, and coal fly ash standard samples were found to be 0.103, 0.067, 0.013, 0.006, 1.267, 0.013, and 0.233 ppm, respectively, versus the certified values of 0.105, 0.044, 0.0058, 0.004, 1.440, 0.063, and 0.16 ppm, respectively. The method is thus suitable for continuous monitoring of mercury and for the fast and reliable determination of mercury in biological and environmental samples, even at background levels.