At-line Determination of Mercury in Process Streams Using Atomic Fluorescence Spectrometry

Abstract

Atomic fluorescence spectrometry (AFS) has been coupled with vapour generation sample introduction for the at-line determination of mercury in concentrated sulfuric acid production streams. Matrix and heat effects were overcome by the use of discrete sample injection techniques. A sample collection and pre-treatment manifold is described in combination with permanganate oxidation and SnCl ₂ reduction chemistries for coupling with a fully automated instrument. Continuous monitoring of single grab samples of concentrated sulfuric acid over periods of 24 and 15 h resulted in precisions of 5.8 and 8.9% RSD and mean mercury concentrations of 1.11 and 1.08 µg g ^-1 , respectively, compared with 1.2 and 0.95 µg g ^-1 obtained by a laboratory based method. The application of the instrument in on-site trials at a sulfuric acid plant is described. The mercury concentration in sulfuric acid was monitored continuously over a period of 10 d without intervention and showed excellent agreement with results of laboratory analyses performed over the same period.