Direct Determimnation of Mercury in Sediments by Atomic Absorption Spectrometry

A pyrolysis chamber is described for the direct determination of mercury in sediments by atomic absorption spectrometry. The finely ground and dried sample is weighed (2.0–60.0 mg), transferred to a quartz cup, inserted in a pyrolysis chamber and heated at 1100 °C for 30 s by means of three focused infrared lamps in the presence of an air stream as the carrier gas. Interfering substances are destroyed by a precolumn containing alumina, silica and copper(II) oxide, and the released mercury is amalgamated on to a gold-coated collector. Mercury vapour is later measured by AAS after thermal desorption. Calibration is easily performed by flow injection, in which known volumes of mercury-saturated air are introduced into the same air carrier stream. The absolute detection limit was 0.26 ng Hg and the relative standard deviation of measurements (n=12) from a typical 4.0 mg sample was about 7%. By applying a t-test, there was no significant difference at the 5% probability level between the results obtained with the proposed method and those certified or recommended for NIST materials. One analysis takes only 2 min, including sample weighing.