Determination of mercury with on-line addition of stannous chloride uUsing an axial ICP-OES
Mercury is one of the most toxic heavy metals in the environment. It is therefore important to routinely monitor the Hg level in many types of samples. The US EPA approved methodology for the determination of Hg uses the cold vapor technique with stannous chloride as the reducing agent1. This methodology is applicable to Hg determinations in a range of waters (drinking, ground, surface, sea and brackish waters) plus domestic and industrial wastes. It allows mercury detection down to the sub-μg/L range. While Hg can be determined with direct aspiration using the ICP-OES technique, the performance achieved is not sensitive enough for many environmental applications. Ultra-trace level determination of Hg therefore requires the use of a vapor generation accessory such as the Varian VGA-77. The detection limit of Hg achieved with this accessory using an axially-viewing ICP-OES is 0.02 μg/L2. However, if the required determination level of Hg is not so low, it is feasible to use on-line addition of reductant to achieve the required signal enhancement. This work demonstrates a simple and convenient way to determine Hg in the μg/L range using an axially-viewing ICP-OES.