Vapor Generation Accessory VGA–77 Operation manual

VGA–774.4.1 AntimonyPrepare samples in at least 1 M hydrochloric acid and ensure that anyanalyte present as Sb V is reduced to Sb III by the action of potassiumiodide at a concentration of 1% w/v. Reduction is spontaneous andheating should not be required.Reductant container: NaBH 40.6%,NaOH 0.5%Acid container:5 to 10 M HCl4.4.2 Arsenic✒ Note If arsenic and selenium are both to be determined from the samesample, determine selenium first, and avoid KI in samples orstandards. You can then determine arsenic after the KI reduction stepand any other appropriate treatment (such as the addition of urea ifexcess nitric acid is present).Arsenic in the sample must be in the inorganic form, otherwisedigestion will be necessary.If digestion is necessary, use acid digestion, ensuring no residualoxidizing acid is present (see section 3.2.2), or ashing with anappropriate ashing aid. Simple dry ashing is not recommended.Prepare samples in at least 1 M hydrochloric acid.Ensure that any analyte present as As V is reduced to As III by the actionof potassium iodide at a concentration of 1% w/v.Reduction will take about 50 minutes at room temperature. Thereduction can also be carried out at 70 °C in about four minutes;however you must cool the samples and standards to roomtemperature prior to analysis. Since the pumping rate may vary withsolution temperature, the VGA-77 pump will not operate correctlywith hot solutions.If the reduction step is omitted, and the analyte is retained asAs V , the analytical sensitivity is about 20-30% of that obtained forAs III . If the original solution contains As III , reduction by potassiumiodide is not required.Reductant container: NaBH 40.6% (see also above)NaOH 0.5%Acid container:5 to 10 M HClPublication date: May 2004 4-7