The determination of chromium in plain carbon steel and low-alloy iron and steel by atomic-absorption spectrophotometry

Co-operative examination of published atomic-absorption procedures for several elements in steel showed good agreement between results apart from those for chromium. For this element the depressive effect of iron in the air-acetylene flame is eliminated when using the preferred nitrous oxide-acetylene flame. However, control of flame composition is essential as vanadium, molybdenum, aluminium and titanium in low-alloy synthetic test solutions and samples increasingly enhance the chromium absorbance with increased fuel richness. Copper, nickel and iron have no effect but, in any event, iron should be included in the calibration solutions. Hence a lean, oxidising flame must be used and the results for samples then agree closely with the certificate values.