Optimisation of experimental parameters for flow injection flame atomic absorption spectrometry

Abstract

Some of the factors that govern the performance of flow injection sample introduction for flame atomic absorption spectrometry were investigated. The parameters taken into consideration include nebuliser uptake rate, carrier flow-rate, air and water compensation at low carrier flow-rates and the effect of the flow spoiler. The peak absorbances for lead and calcium for nebuliser uptake rates in the range 0–10 ml min^–1 and carrier flow-rates in the range 0.2–6 ml min^–1 with a sample injection volume of 430 µl with and without air compensation are depicted in three-dimensional graphs. Only in extreme instances was air compensation necessary for good sensitivity and precision. Without air or water compensation the flow injection sample introduction system could be optimised to provide a sensitivity 5–10% better than that obtained using conventional sample introduction. Precision and detection limits similar to those for conventional sample introduction could be attained at carrier flow-rates of 0.9–6 ml min^–1 within a fairly wide range of nebuliser uptake rates with and without air compensation, and using the flow spoiler. Without the flow spoiler, precision tends to be poorer, as is true for extremely low carrier flow-rates of 0.4 ml min^–1 and high nebuliser uptake rates without air compensation.