Comparison of three propulsion systems for application in flow-injection zone penetration dilution and sorbent extraction preconcentration for flame atomic absorption spectrometry

Abstract

Better precision can be achieved in flow-injection on-line dilution for flame atomic absorption spectrometry by zone penetration using knotted reactor sample loops and transport conduits than with straight conduits. About a 2% R.S.D. was obtained for a dilution factor of 20 using the valley between two peaks with a peristaltic and a reciprocating piston pump. A sinusoidal syringe pump gave an inferior precision of 8% R.S.D. under the same conditions owing to a lack of proper interfacing between such pumps and the atomic absorption spectrometer. On-line sorbent extraction column preconcentration was shown to be feasible using sinusoidal and reciprocating pump systems, which obviated the need for solvent-proof pump tubes. However, both systems had to be supplemented by peristaltic pumps. Air segmentation between sample and eluent was found to be effective in preventing dispersion at the interface when sample loading and elution were performed in one piston stroke of the sinusoidal pump. The concentration efficiency (15−18 min −1) and short-term precision (ca. 2% R.S.D.) of both preconcentration systems were generally comparable to those of previously reported systems for sorbent extraction preconcentration with time-based sampling, but the long-term precision of the piston and syringe pump systems (4−5% R.S.D.) was better than that of the time-based peristaltic pump sytem (10−20% R.S.D.).