Vapor Generation Accessory VGA–77 Operation manual

VGA–774.4.5 Selenium✒ Note See also section 4.4.8 ‘Additional notes’ at the end of this section.The selenium in the sample must be in the inorganic form, otherwisedigestion will be necessary.If digestion is necessary, use acid digestion, or ashing with anappropriate ashing aid. Simple dry ashing is not recommendedbecause selenium is highly volatile and recovery will be poor.Se VI is not quantitatively recovered by hydride generation and must bereduced to Se IV by warming with concentrated hydrochloric acid.Prepare the samples in 6-7 M hydrochloric acid (use of a lower acidconcentration will result in greater inter-element interferences), heatat 70-90 °C for at least 10 minutes. Cool to room temperature beforeanalysis.Reductant container: NaBH 40.6%NaOH 0.5%Acid container:10 M HCl4.4.6 TelluriumThe presence of potassium iodide will severely suppress the analyticalresponse. Always ensure that the VGA-77 system is completely free ofpotassium iodide before performing tellurium determinations.✒ Note To avoid contamination, it is recommended that you dedicate aseparate module to the analysis of those elements requiring prereductionwith KI (i.e. As or Sb).Te VI is not quantitatively recovered by hydride generation and must bereduced to Te IV . Prepare the samples in 6-7 M hydrochloric acid, heatat 70-90 °C for at least 10 minutes and cool to room temperaturebefore analysis.Reductant container: NaBH 40.6%NaOH 0.5%Acid container:5 M HCl (Higher acid concentrations willreduce the analytical signal.)4-10 Publication date: May 2004