Electrocatalysis of sulphide with a cellulose acetate film bearing 2,6-dichlorophenolindophenol. Application to sewage using a fully automated flow injection manifold

The application of an electrochemical sensor, based on a glassy carbon elec trode, modified with a cellulose acetate polymeric film bearing 2,6-dichlor ophenolindophenol (CA/DCPI-CME), for flow injection analysis of sulphide, i s described. The overall reaction was found to obey a catalytic regeneratio n mechanism (EC mechanism) and the: electrochemical rate constant k(f) for the electrocatalytic oxidation of sulphide was evaluated. The modified elec trodes were mounted in a flow-injection manifold, poised at + 0.08 mV versu s Ag/AgCl/3 M KCI at pH 7.25 and utilised for the determination of sulphide in urban waste samples. The proposed method correlates well with a colorim etric method. Parameters such as working pH, sample size, flow rate and tem perature were studied. Interferants of various compounds normally present i n real samples were also tested. Calibration graphs were linear over the ra nge 0.02-1 mM sodium sulphide for CA/DCPI-CMEs hydrolysed in KOH for 6 min. The throughput was 25 samples per h and the R.S.D. was 1.3% (n = 7) for 0. 1 mM sodium sulphide. Recoveries for spiked urban waste samples ranged from 99 to 120%. The sensor remained active for more than 2 weeks under specifi ed conditions. (C) 2000 Elsevier Science B.V. All rights reserved.