Sequential injection analysis system for the determination of hydride-forming elements by direct current plasma atomic emission spectrometry

Abstract

A method for the determination of volatile hydride-forming elements with direct current plasma atomic emission spectrometry (DCP-AES) based on a modified version of the sequential injection analyser has been developed. The sequential injection (SI) hydride generator consists of two multi-port valves and a piston burette. The burette is also used as a dynamic reaction chamber the volume of which can be changed by the piston movement. This arrangement allows isobaric reaction. The burette also functions as a gas–liquid separator where the liquid reaction products are drained via a channel through the piston head. The hydride gases are pumped by the piston into the plasma through a thin quarts capillary, which is also used to position the direction of gas flow to the centre of the plasma. All functional parts in this system are computer controlled. The performance of the SI hydride generation DCP-AES system has been tested in the determination of arsenic, bismuth and germanium. The detection limits (3s) were 0.15, 0.08 and 0.03 µg l^–1, respectively. The calibration graphs were linear (r >0.999) in the concentration ranges studied: 0–50 µg l^–1 for arsenic and 0–10 µg l^–1 for bismuth and germanium. The relative standard deviation for all three elements was less than 10% at a concentration level of 1 µg l^–1 and ≈3% at the 10 µg l^–1 level. The accuracy of the method was tested in the determination of arsenic in the National Institute of Standards and Technology (NIST) Standard Reference Materials, NIST SRM 1573 Tomato Leaves and NIST SRM 1575 Pine Needles.