Determination of arsenic and antimony by microwave plasma atomic emission spectrometry coupled with hydride generation and a PTFE membrane separator

The performance of a microwave plasma torch (MPT) discharge atomic emission spectrometry (AES) system directly coupled with hydride generation (HG) fo r the determination of As and Sb has been studied. The argon MPT system can sustain a stable plasma over a wide range of carrier and support gas flow rates with optimum performance at 250 and 1450 ml min(-1), respectively. Th e presence of trace amount of water in the MPT discharge is found to affect the detection limits and the signal to noise ratio. A PTFE membrane separa tor is applied for hydride introduction and water rejection. In addition, t he membrane cell separator also improves the signal to noise ratio by servi ng as a pressure buffer to minimize noise due to pressure fluctuation. Dete ction limits (3 sigma) of 8.1 and 3.2 ng ml(-1) are obtained with the analy tical lines As I 228.812 nm and Sb I 259.809 nm, respectively at an MPT pow er of 135 W. The detection limits are improved when a concentrated sulfuric acid cell is placed after the membrane cell to further remove water. This double cell system yields detection limits of 5.3 and 2.1 ng ml(-1) for As and Sb, respectively under the same operating conditions. Linear dynamic ra nges of three orders of magnitude could be obtained. (C) 2001 Elsevier Scie nce B.V. All rights reserved.