Use of low termperature ashing and microwave acid extraction procedures for As and Hg determination in coal, coal fly ash, and slag samples by cold vapor/hydride generation AAS

摘要

Methods for the determination of As and Hg in coal, coal fly ash, and slag samples involving microwave acid extraction and cold vapor/hydride generation AAS have been developed. Two microwave acid extraction procedures using aqua regia and aqua regia + hydrofluoric acid were studied. For samples with high organic matter content (coal samples), a low temperature ashing pre-treatment (LTA) (below 150 deg C) was carried out prior to microwave acid extraction. The results were compared to those obtained without a LTA pre-treatment. Satisfactory analytical recoveries were obtained for As, while around 18 percent of rig was removed during the LTA pretreatment. Mercury cold vapor and arsenic hydride were generated from hydrochloric acid medium using sodium tetrahydroborate in a batch hydride generation system coupled to AAS. The LODs obtained were 0.20 and 0.15 #mu#g L~(-1) for As and Hg, respectively. The accuracy was studied using NIST-1633b coal, NIST-1635 coal, and NIST-1632b coal fly ash referencematerials. The methods were applied to several coal, coal fly ash, and slag samples.