Alternative method for mercury detection using square wave anodic striping voltammetry

Abstract

By the time the pipelines and other facilities reach their service lives and are to be decommissioned, Mercury (Hg) shall be assessed and monitored as per regulations and for the sake of health and environment care. Company and research institute partners have been therefore developing innovative method to prove the cleanliness of the pipelines and other facilities especially for on-site works. In general, spectrophotometry such as cold-vapor atomic absorption spectrometry is proposed to be as standard technique to measure Hg level in samples. Even though this method is sensitive for lowconcentration detection, to meet the sensitivity requirement, it needs extensive sample preparation and long analysis time. Consequently, this technique is not suitable for analysis at worksites. Therefore, a sensitive, selective, rapid and portable Square Wave Anodic Striping Voltammetry (SWASV) has been developed for the determination of ultra-trace levels of Hg in samples. Hg is contaminant and inherently found in Oil and Gas production and operation assets, especially in the Gulf of Thailand. It may interact and remain in pipelines and other facilities in the production and operation conditions. The level of Hg contamination is normally so low that some specific methodologies based on chemical laboratory are required to confirm such low concentration level (ppb to ppm level). However, it is not common to set-up laboratory station for Hg detection such as cold-vapor atomic absorption spectrometry at worksites especially at offshore remote well head platforms. SWASV could be therefore an alternative method to detect and screen Hg-contaminated pipelines and facilities. The method does not require any separation or pre-concentration steps and is directly applied to determine levels of Hg in environmental or retreived samples. The comparison between the proposed SWASV and ICP-OES standard method was performed on the samples, the concentrations obtained by both methods were in agreement with the certified values of Hg, according to the paired t-test at 95% confidence level. SWASV is therefore being developed further to put into mobile lab (poratbale tool). The proposed method is capable of analyzing Hg on-site, reducing total analysis time and monitoring very low concentration of Hg (even down to ppb level) with simple preparation and operation. It could be therefore recommended as an alternative option or as screening method to analyze various samples contaminated with Hg as part of decommissioning activities. © Copyright 2019, Society of Petroleum Engineers