Highly sensitive potentiometry for determination of chromium(VI) with carbon paste electrode

Abstract

Trace-level Cr₂O₇^2– was determined in 2.0 mol dm^–3 H₂SO₄(at 20 °C) with a carbon paste electrode (mixture of liquid paraffin and spectroscopically pure graphite powder, without ionophore) by using a potentiometric method with the linear range within 2.2 × 10^–7–3.2 × 10^–6 mol dm^–3, response slope at 130–180 mV decade^–1, and a detection limit at 3 × 10^–8 mol dm^–3. The respective interferences by 22 common ions were brought under study. An evaluation was made of the recovery of Cr₂O₇^2–, with an average value of 99.7%. This method is characterized by simplicity, convenience and speed.