Carbon paste electrode modified with chromium thiopental for the potentiometric flow injection analysis of chromium (III)

A chemically modified carbon paste electrode for chromium (III) based on the formation of ion-association complex of chromium with 5-ethyl-6-oxo-5-pentan-2-yl-sulfanyl-pyrimidin-4-olate (thiopental, THP) as electroactive ion-exchanger (Cr-THP) was prepared and investigated. The electrode has a linear dynamic range of 1.7?×?10^?6–1.3?×?10^?2?mol?L^?1, with a Nernstian slope of 19.6?±?0.5?mV per decade and a detection limit of 9.0?×?10^?7?mol?L^?1. It has a fast response time of <15?s and can be used for at least 7 weeks without any considerable divergence in potential. The proposed sensor revealed good selectivity for Cr(III) over a wide variety of mono-, di-, and trivalent cations and could be used in the pH range of 2.3–6.5. The proposed electrode was used in batch measurements and in flow injection analysis. The Cr-CMCPE was successfully applied for the determination of Cr(III) in real samples (wastewater of hot dip galvanizing unit and alloys). The present electrode was also used as an indicator electrode in potentiometric titration of Cr(III). The results were highly satisfactory.