Automated continuous monitoring of inorganic and total mercury in wastewater and other waters by flow-injection analysis and cold-vapour atomic absorption spectrometry

S E Birnie

doi:10.1155/s1463924688000264

Abstract

An automated continuous monitoring system for the determination of inorganic and total mercury by flow-injection analysis followed by cold-vapour atomic absorption spectrometry is described. The method uses a typical flow-injection manifold where digestion and reduction of the injected sample takes place. Mercury is removed by aeration from the flowing stream in a specially designed air-liquid separator and swept into a silica cell for absorption measurement at a wavelength of 253.7 nm. A calibration curve up to 10 μg Hg ml-1 using three different path length cells is obtained with a detection limit of 0.02 μg Hg ml-1. The sampling rate of an injection every 3 min produces 20 results per hour from a flowing stream.

Highlights

The determination of mercury in aqueous solution at low concentrations is usually carried out by the Cold Vapour Atomic Absorption (CVAA) method which was introduced by Puleukov et al [1] and Hatch and Ott [2]
The method is based on the chemical reduction of mercury ions to elemental mercury, usually with SnCI2 or NaBH4
The elemental mercury is swept out of solution with a carrier gas into an absorption cell where the atomic absorption at 253.7 nm is measured. This procedure normally uses a discrete sample method in which all the mercury from a given volume of solution is swept through the absorption cell to produce a peak response

Summary

Introduction

The determination of mercury in aqueous solution at low concentrations is usually carried out by the Cold Vapour Atomic Absorption (CVAA) method which was introduced by Puleukov et al [1] and Hatch and Ott [2]. The elemental mercury is swept out of solution with a carrier gas into an absorption cell where the atomic absorption at 253.7 nm is measured This procedure normally uses a discrete sample method in which all the mercury from a given volume of solution is swept through the absorption cell to produce a peak response. Many improvements to the method, Hawley and Ingle [3], Christmann and Ingle [4] have reduced the detection limit to 2 pg in a ml sample This method is widely accepted as a standard for determining traces of mercury in aqueous solutions and is well documented. SPIRAL COIL (4) Reducing reagent, 10% m/v tin (11) chloride dissolved in 10% v/v hydrochloric acid solution, Spectrosol low in mercury grade (BDH Ltd). (3) Oxidizing reagentT 4% m/v potassium persulphate solution, laboratory reagent, low in mercury grade (BDH Ltd)

Procedure

Results and discussion

Conclusion