Determination of Total Mercury in Soil Using the Automatic Mercury Analytical System

Study on the determination of total mercury in soil was performed using the Hydra C automatic mercury analytical system. The soil sample was pulverized to pass through sample sieve with aperture size of 0.15 mm. A portion of soil sample (0.1 g) was placed into the sample boat and introduced automatically into the pyrolysis furnance of the analyt. system by the carrier gas of oxygen, and proceeded to stages of drying (at 300 ℃), pyrolysis (at 800 ℃) and catalytic reduction (at 600 ℃) after which mercury was selectively isolated by amalgamation with gold. Mercury was then liberated from the amalgam by heating and the Hg vapour was passed through absorption cell and its absorbance measured by AAS at the wavelength of 253.65 nm. CRM′s of soil were used for preparation of 2 standard curves in the linearity ranges of within 30.0 ng and between 30.0-300.0 ng by the analyt. system automatically. Precision was tested with 2 samples containing of Hg, and values of RSD′s (n=6) obtained were all less than 2.0%. Ten determinations were carried out without and with (0.1 g) sample, values of detection limits (3s) found for the instrument and for the method were 0.022 ng and 0.082 ng respectively. Seven soil CRM′s were analyzed by the present method and by the AFS method, as shown by the result of t-test, no significant difference was found between the results of the 2 methods.