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

A computer-controlled manifold allowing the automatic collection of concent ration profiles for use in flame atomic absorption spectrometry (FAAS) is d escribed. For this purpose a standard solution is pumped at an increasing f low rate, the difference between this flow rate and the nebulizer uptake ra te being compensated with water. Next, the sample solution is pumped at a d ecreasing rate. A 50-s gradient time is used. The absorbance-time profiles thus obtained intersect at a point which permits the concentration to be ca lculated. The system allows the on-line dilution of solutions which are too concentrated to be measured by direct aspiration. Using a 30 mu g ml(-1) c alcium standard solution for calibration, this analyte can be determined in the 1-200-mu g ml(-1) range with relative errors below +/-1%. (C) 2090 Els evier Science B.V. All rights reserved.