Flow injection flame atomic absorption analysis of Fe and Mn in cement samples

A new procedure has been developed for the determination of Fe and Mn in cements. It consists in dispersing 50 mg of the solid sample in 25 ml of 0.15 mol/l HNO3 and 0.12 mol/l HCl solution. Acid slurries are heated at 50°C for 10 min and then different volumes of the slurry are injected into a water carrier stream. This previous acid treatment leaches the elements to be determined and permits the use of acid solutions as standards. For the Mn determination, the use of a single line flow injection manifold provides a limit of detection of 0.03 mgl−1 and a dynamic range up to 6 mgl−1. For the determination of Fe, the on-line dispersion of samples, using a well stirred mixing chamber, increases the dynamic range up to a concentration of 125 mgl−1 and provides a limit of detection of 1 mgl−1. The procedure has been applied to the analysis of real cement samples and a certified reference material. Results were in agreement with those obtained by a reference procedure involving the alkaline fusion of samples and batch analysis by flame atomic absorption spectrometry.