Vapor Generation Accessory VGA–77 Operation manual

VGA–774.4.3 BismuthThe presence of potassium iodide will severely suppress the analyticalresponse. Always ensure that the VGA-77 system is completely free ofpotassium iodide before performing bismuth determinations.✒ Note To avoid contamination, it is recommended that you dedicate aseparate module to the analysis of those elements requiringpre- reduction with KI—As, Sb.Prepare samples in 1 M hydrochloric acid.Reductant container: NaBH 40.6%NaOH 0.5%Acid container:5 M HCl (Higher acid concentrations willdepress the analytical signal.)4.4.4 MercuryTraces of potassium iodide will interfere severely with the productionof mercury vapor and the analytical response may be completelysuppressed. Always ensure that the VGA-77 system is completely freeof potassium iodide before performing mercury determinations.✒ Note To avoid contamination, it is recommended that you dedicate aseparate module to the analysis of those elements requiring prereductionwith KI—As, Sb.The mercury in the sample must be in the inorganic form, otherwisedigestion or use of releasing agents (e.g. CdCl 2), will be necessary.If digestion is necessary, use acid digestion, or ashing with anappropriate ashing aid. Simple dry ashing is not recommended as themercury will be lost.Dilute mercury solutions tend to be unstable; all analytical solutionsshould be stabilized by the addition of nitric acid (5% v/v) andhydrochloric acid (5% v/v). Prepare fresh standards daily.Á*GÁZPVÁBSFÁVTJOHÁUIFÁ""ÁNPEVMFÁAcceptable results can be obtained with the standard absorptioncell, however the flow-through mercury cell is recommendedsince this will generally provide better analytical sensitivity andprecision.4-8 Publication date: May 2004