A flow injection system based on chalcogenide glass sensors for the determination of heavy metals

A flow injection set-up for the determination of Pb(II), Cr(VI), Cu(II), Cd (II) using chalcogenide glass chemical sensors (electrodes) is presented. S even electrodes are used to determine the four metals and also chloride ion s and the signals are analysed using multivariate analysis method, includin g artificial neural networks. The background solution is 1 M nitric acid. I t is divided in two Lines where the first one is mixed with 1.2 M sodium ac etate and the other one is 1 M nitric acid. The Hg(II), Cr(VI) and Ag(I) se nsors are placed in the acid line while the Pb(II), Tl(I), Cd(II) and Cu(II ) electrodes are placed in the buffered line. The detection limit for Pb(II ) was about 3 mu M and about 1 mu M for the other metals. In our system chl oride can be determined down to about 1 mu M alone and 20 mu M simultaneous ly with the other species. The average error for the determination of the m etals in the range from the detection limit up to about 3 mM was 10-15% for Pb(II), Cr(VI), Cu(II) and Cd(II) and about 30% for Cl-. The parameters fo r the flow injection system were: flow rate 0.5 ml/min and sample Volume 50 0 mu l. The peak widths were 100-300 s allowing a theoretical measurement r ate of 15 per hour. In practice, sampling rates of about 7-10 times per hou r are realistic. The system is developed as a step forward to on-line measu rements of exhaust gases from waste incineration plants. (C) 2000 Elsevier Science B.V. All rights reserved.