Automated on-line preconcentration of trace aqueous mercury with gold trap focusing for cold vapor atomic absorption spectrometry

• Published in: Talanta (Oxford) Vol. 99; pp. 1040 - 1045
• Main Authors: Puanngam, Mahitti, Dasgupta, Purnendu K., Unob, Fuangfa
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.09.2012; Elsevier
• Subjects: Adsorption; Analytic Sample Preparation Methods - methods; Analytical chemistry; Argon - chemistry; Automation; Chemistry; Chlorides - chemistry; Cold Temperature; Cold vapor atomic absorption spectrometry; Environmental Pollutants - analysis; Environmental Pollutants - chemistry; Exact sciences and technology; General, instrumentation; Gold - chemistry; Gold trap; Mercury; Mercury - analysis; Mercury - chemistry; Online Systems; Reference Standards; Solid phase preconcentration; Spectrometric and optical methods; Spectrophotometry, Atomic - methods; Spectrophotometry, Atomic - standards; Volatilization; Water - chemistry; Cold vapor atomic absorption spectrometry; Gold trap; Mercury; Solid phase preconcentration; Water; Fold; On line; Tetrahydroborates; Instrumentation; Thioureas; Chemical enrichment; Mercury ion; Improvement; Sample preparation; Loading; Chlorides; Detection limit; Tungsten; Thiourea; Silica gel; Argon; Trace analysis; Gold; Automation; Sample; Use; Method; Water vapor; Automatic processing; Sorption; Vapor phase; Sodium; Cold vapor; Reference material; Solid phase; Atomic absorption spectrometry
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2012.05.055

A fully automated system for the determination of trace mercury in water by cold vapor atomic absorption spectrometry (CVAAS) is reported. The system uses preconcentration on a novel sorbent followed by liberation of the mercury and focusing by a gold trap. Mercury ions were extracted from water samples by passage through a solid phase sorbent column containing 2-(3-(2-aminoethylthio)propylthio)ethanamine modified silica gel. The captured mercury is released by thiourea and then elemental Hg is liberated by sodium borohydride. The vapor phase Hg is recaptured on a gold-plated tungsten filament. This is liberated as a sharp pulse (half-width<2s) by directly electrically heating the tungsten filament in a dry argon stream. The mercury is measured by CVAAS; no moisture removal is needed. The effects of chloride and selected interfering ions were studied. The sample loading flow rate and argon flow rates for solution purging and filament sweeping were optimized. An overall 50-fold improvement in the limit of detection was observed relative to direct measurement by CVAAS. With a relatively modest multi-user instrument we attained a limit of detection of 35ngL−1 with 12% RSD at 0.20μgL−1 Hg level. The method was successfully applied to accurately determine sub-μgL−1 level Hg in standard reference water samples. ► A fully automated on-line preconcentration of trace Hg with gold trap focusing for CVAAS is proposed. ► The technique shows 50-fold improvement in detection limit compared to direct measurement by CVAAS. ► The detection limit of 0.035μgL−1 was achieved. ► The technique enables a relatively modest instrument to determine sub-μgL−1 level Hg in samples.