FLAME ATOMIC-ABSORPTION SPECTROMETRY FOR ALKALI DETERMINATION IN LIMESTONE AND RELATED MATERIALS USING SIMPLE MATRIX MODIFIER

Abstract

Based on detailed study of the interference effects encountered at sodium resonance line at 589.0 and that of potassium at 767.5 nm, a method has been developed for the determination of sodium and potassium in standard reference materials (limestones: KH, KH2, KH3, CCH-1, JLs-1; dolomites: DWA-1, JDo-1 and anhydrite AN) containing relatively low levels of alkalis required for very crucial quality control (QC) procedure in steel industries. Samples were digested in two steps: first by using 5 mi of HClO4 (70%) and secondly by a mixture of HF (40%) + HCl (11 mol l(-1)) + H2SO4 (1:1)[10 + + 10 + 5. An excellent agreement with the certified values was achieved using lanthanum (1000 mu g ml(-1)) and rubidium (2000 mu g ml(-1)) for sodium and potassium, respectively, except for potassium in Japanese reference materials JLs-1 and JDo-1 indicating that, more data for them are still required for assigning their certified values. The values for alkalis in the samples using commonly used buffers are also presented The Student's t-test values indicate that at a confidence level of 95-99% there is no statistical difference between the flame atomic absorption spectrometric results and the reference material data.