Ultra-trace determination of mercury by platinum-coated tungsten coil trapping cold vapour atomic absorption spectrometry

Abstract

ABSTRACT Within the scope of this study, a simple, highly sensitive and rapid trapping method for the determination of mercury (Hg) was developed. In this method, the surface of the tungsten coil (W-coil) was coated with platinum using the electrolytic deposition technique. Scanning electron microscopy–energy-dispersive X-ray analyses were performed to examine the surface morphology of Pt-coated W-coil. During the experiment, firstly, Hg vapour generated by tetrahydroborate, used as a reducing agent, was efficiently trapped on the Pt-coated W-coil at collection temperature in hydrochloric acid medium. Subsequently, Hg trapped on the surface of the Pt-coated W-coil was revolatilised by the effect of releasing-stage gases at the optimised releasing temperatures and transported to quartz T-tube atomiser. The experimental conditions have been optimised. Under the optimised conditions, a limit of detection (LOD) of 8.8 ng L−1 was obtained using three times the standard deviation of blank values using Pt-coated W-coil trap cold vapour atomic absorption spectrometry (CVAAS) system. The precision of the measurements was evaluated by relative standard deviation of 4.4%, which is obtained by 11 consecutive measurements of reagent blanks for a collection volume of 6.83 mL corresponding to 90 s collection. The enhancement factors for both LOD (3 s) and characteristic concentration (Co) were found to be 5.09 and 5.02 when compared with the regular CVAAS system without trap. The accuracy of the proposed method was evaluated by analysing BCR 146 R (Sewage sludge), RTC (Sandy Loam 7), ERM-BD151 (skimmed milk powder) and NIST 1641e (mercury in water) certified reference materials (CRMs). There was a good agreement between certified and found values for all CRMs. The results of the application of the developed method in seawater showed the spike recovery ranges from 94.2% to 102.4%.