CRITICAL-EVALUATION OF THE EFFICIENCY AND SYNERGISTIC EFFECTS OF FLOW-INJECTION TECHNIQUES FOR SENSITIVITY ENHANCEMENT IN FLAME ATOMIC-ABSORPTION SPECTROMETRY

Mathematical models for evaluating sensitivity enhancement effects of batch off-line and flow injection (FI) on-line preconcentration systems for flame atomic absorption spectrometry (FAAS) are proposed. The performance of four different FI preconcentration systems, including preconcentration by ion exchange, sorbent extraction and coprecipitation, with additional enhancement effects from organic solvents and slotted-tube atom traps, are critically evaluated in terms of apparent enrichment factors, enhancement factors, concentration efficiency and consumptive index. The experimental results show good agreement with calculated results based on equations of the mathematical model. The synergistic effects of different enhancement approaches are illustrated by the determination of lead by FAAS using an FI coprecipitation preconcentration system equipped with a slotted-tube atom trap. A 135-fold sensitivity enhancement was achieved at a sampling frequency of 72 h-1 and with the consumption of 2.7 ml of sample solution.