Multisyringe flow injection system for total inorganic selenium determination by hydride generation-atomic fluorescence spectrometry

摘要

A new multisyringe flow injection system for total inorganic selenium determination by hydride generation-atomic fluorescence spectrometry (HGAFS) has been proposed. The flow methodology is based on the simultaneous injection of sample in the acid media (50% HCl), a reducing sodium tetrahydroborate solution (0.18%) and a solution of hydrochloric acid (50%) which are dispensed into a gas-liquid separation cell by using a multisyringe burette coupled with one multiport selection valve. The usage of the time-based injection increases the sample throughput and provides precise known volumes of sample. The hydride of selenium is delivered into the flame of an atomic fluorescence spectrometer by means of an argon flow. A hydrogen flow has been used to support the flame. The technique can be applied over a wide range of concentrations of selenium between 0.1 and 3.5 mug 1~(-1) with good repeatability (relative standard deviation (R.S.D)) values 4.6-7% or 1 mug 1~(-1) of Se). The detection limit of the developed technique (3sigma_b/S) was 0.01 mu g 1~(-1). A sample throughput was 28 samples per hour (84 injections). The multisyringe technique has been validated by means of reference solid (sea lettuce) and water (hard drinking water) materials with good agreement with certified values. The analytical features were compared with those obtained by using of the commercial flow injection analysis (FIA) system. The proposed method provides a higher sampling frequency and a significant reduction of reagent and sample consumption in front the flow injection application.