CATALYTIC DETERMINATION OF PERCHLORATE USING A MODIFIED CARBON-PASTE ELECTRODE

A method for the catalytic voltammetric determination of perchlorate u sing a carbon paste electrode modified with a liquid anion exchanger i s presented. The fundamental catalytic effect is based on the chemical reoxidation of electrochemically generated T1(0) by perchlorate which can be monitored by an increase of the corresponding current flow. Pe rchlorate can be preconcentrated, together with tetrachlorothallate(II I) as a catalyst, from hydrochloric acid solutions onto the modified c arbon paste electrode under open circuit conditions. For analytical pu rposes, the increase of the current response for the reoxidation of T1 (0) to T1(I) is exploited for quantifications. Methodical parameters s uch as pH, ionic strength of the media, preconcentration time and thal lium concentration are investigated; the influence of interferents is studied. The dependence of the current increase on the concentration o f perchlorate with different accumulation times is presented. The dete ction limit (3 sigma) is 50 mu g . l(-1) ClO4- (12 min accumulation). To show the applicability of the method to the analysis of real sample s spiked drinking water was investigated.