Chlorine-interference-free Sample Treatment of Stainless Steel to Prepare Glass Bead Specimens for Chromium Quantification by X-ray Fluorescence Spectrometry

This report describes improved X-ray fluorescence analysis to quantify chromium as a major constituent of stainless steel and cobalt–chromium alloy samples. Stainless steel can be digested rapidly using hydrochloric and nitric acids, including aqua regia, for wet chemical analyses using atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, and inductively coupled plasma mass spectrometry. Nevertheless, because of chromium volatilization as chromyl chloride in fusion processes during glass bead preparation, this acid digestion is inapplicable for glass bead specimens of chromium-containing materials intended for use in X-ray fluorescence spectrometry. For the work described herein, microwave digestion using nitric and hydrofluoric acids was used to prepare appropriate glass bead specimens. The X-ray absorption and enhancement were negligible for the present glass bead specimens. An extremely high 2000-times dilution of 4000 mg lithium tetraborate and 2 mg sample was used. Reliable analytical values of chromium were obtainable using the suggested X-ray fluorescence analysis without matrix correction calculation.