A variable dispersion flow injection manifold for calibration and sample dilution in flame atomic absorption spectrometry

A flow injection (FI) introduction system for flame atomic absorption spectrometry (FAAS) has been constructed for single-standard calibration and sample dilution. Dilution factors ranging from 5.93 to 38.8 in six discrete stages were produced by replicate injection of 12.5-µl volumes into an aqueous carrier stream flowing down lines of different lengths. The dilution factors were measured for five different solutions for each line. No dependence on concentration was found and the relative standard deviations ranged from 0.75 to 3.1%. The manifold was evaluated by the analysis of solutions of magnesium (6, 12.5 and 35 p.p.m.), nickel (180 p.p.m.), calcium (75 p.p.m.) and chromium (180 p.p.m.). Recoveries ranging from 95.3 to 106.8% were obtained with no over-all evidence of bias. The uncertainty in the over-all method, including a contribution from the curve-fitting procedure, was estimated to be 5%.