Calibration in flame atomic absorption spectrometry using time-dependent concentration profiles

A computer-controlled manifold allowing the automatic collection of concentration profiles for use in flame atomic absorption spectrometry (FAAS) is described. For this purpose a standard solution is pumped at an increasing flow rate, the difference between this flow rate and the nebulizer uptake rate being compensated with water. Next, the sample solution is pumped at a decreasing rate. A 50-s gradient time is used. The absorbance–time profiles thus obtained intersect at a point which permits the concentration to be calculated. The system allows the on-line dilution of solutions which are too concentrated to be measured by direct aspiration. Using a 30 μg ml−1 calcium standard solution for calibration, this analyte can be determined in the 1–200-μg ml−1 range with relative errors below ±1%.