Flow injection on-line dilution for flame atomic absorption spectrometry by micro-sample introduction and dispersion using syringe pumps

A robust flow injection (FI) on-line dilution system based on micro-sample introduction was developed for flame atomic absorption spectrometry (FAAS). Two computer programmed and stepper-motor driven syringe pumps were used for the precise and reproducible sample metering in micro-liters and carrier delivery. Factors, which might influence the performance of the system, such as sample matrix and carryover, were investigated. No inferior effects were observed with various matrices including 10% glycerol. Sample carryover effects were less than 0.4%, tested by analyzing a blank and a sample alternately. Dilution factors were decided and keyed in manually. The system was calibrated using a set of concentrated standard solutions for a given dilution factor. At a sampling frequency of 60 h⁻¹, precisions were better than 2% R.S.D. (n=40) for dilution factors of 10-2000. The long-term stability of the system was examined by continuously running the system for a whole working day, and a precision of 2.6% R.S.D. (n=345) was obtained at a dilution factor of 1000. The system was verified by analyzing a standard copper alloy with a certified concentration of 57.4% Cu, resulting in a measurement solution with 574 mg l⁻¹ Cu.