Analysis of HgT in Water by Manual Purge and Trap Capture Fluorescence

Analysis of Total Mercury in Water by Manual Purge and Trap Capture and Cold Vapor Atomic Fluorescence Detection

The following standard operating procedure (SOP) is used by the U.S. Geological Survey’s Mercury Research Laboratory (MRL) to determine total mercury (HgT) concentrations in water. This SOP describes the preparation of the sample and subsequent analysis. Samples are collected into Teflon bottles and preserved to 1% v/v with MRL-supplied Hydrochloric Acid. Bromine Monochloride (BrCl) is added to the sample and heated to 50°C for five days to release matrix-bound mercury and oxidize all forms of mercury to the Hg2+ oxidation state. Immediately prior to analysis, the BrCl is neutralized by the addition of Hydroxylamine Hydrochloride (NH2OH*HCl). Following neutralization, Stannous Chloride (SnCl2) is added to the sample to reduce the mercury from Hg2+ to Hg0 . The volatile Hg0 is purged from the sample and captured onto a gold bead trap (sample trap). The Hg0 is thermally desorbed from the sample trap and captured onto a second gold trap (analytical trap). The Hg0 is desorbed from the analytical trap and detected by cold vapor atomic fluorescence spectrometry (CVAFS) with a Tekran 2500. Quality assurance and control protocols are employed throughout sample preparation and analysis, including: laboratory practices to prevent sample contamination, method blanks, analytical replication and matrix spikes, and analysis of quality control standards (QCS).

Mercury Research Laboratory, 2016