Potentiometric detection of citrate in beverages using a graphite carbon electrode

The development, evaluation and application of a simple and low-cost graphite carbon electrode for the direct determination of citrate in food samples are described here. The electrode exhibits a linear response with a slope of -29.0 +/- 1.0 mV decade(-1) in a concentration range of 0.07-7.0 mmol L-1 in 0.1 mol L-1 KCl/1.0 mmol L-1 phosphate buffer solution with a limit of detection of 3.0 mu mol L-1. The electrode is easily constructed at a relatively low cost and has a fast time response (within 120 s) with no significant changes in its performance characteristics. The performance of the graphite sensor was tested to determine citrate in beverage samples (juices and an isotonic drink), and the results were validated against a reference procedure. The proposed method is quick, inexpensive, selective and sensitive, and is based entirely on conventional instrumentation. (C) 2011 Elsevier B.V. All rights reserved.