Continuous Micro Flow Analysis System for Monitoring Total Mercury at Sub-ppb Level in Wastewater

Abstract

An automated continuous monitoring system for total mercury at sub-ppb level based on cold-vapor atomic absorption spectrometry—“continuous micro flow analysis” is described. The method uses continuous flow sample digestion, reduction and extraction in small bore tubes (0.25 mm i.d.) at very slow flow rates of reagents (17–23 μl min⁻¹). On descrete injection of sample (180 μl), analytical time for the determination of total mercury was about 4 min per one sample. The detection limit of mercury(II) was about 0.15 μg l⁻¹ (S/N=3) using a gas flow cell with 40 mm lightpass length; the relative standard deviation for the measurement at 2 μg l⁻¹ level was 1.2% (n=5). On continuous micro flow injection of sample at a flow rate of 180 μl min⁻¹, the system was successfully applied to the completely continuous monitoring of total mercury in wastewater.