Electrochemical Detection of Amaranth in Food Based on the Expanded Graphite Paste Electrode

A sensitive and simple electrochemical method was developed for successful determination of amaranth in food samples by square-wave adsorptive stripping voltammetry based on an expanded graphite paste electrode (EGPE). The EGPE has strong and sensitive voltammetric responses to amaranth, owing to the multiporous structure and large surface area of EG. The electroanalytical determination of this azo dye was found to be optimal in Britton-Robinson buffer solutions (pH 7.0) under the following experimental conditions: accumulation time, 400 s; accumulation potential, 0.4 V; pulse amplitude, 25 mV; and frequency, 10 Hz. Under the optimum experimental conditions, the oxidation peak current was proportional to the concentration of amaranth over two ranges from 0.01 to 0.1 and 0.1 to 4.0 μM. These linear ranges of the EGPE toward amaranth were wider than other electrodes reported before. The LOD was estimated to be 0.005 μM (S/N = 3:1). The developed method was applied to the determination of amaranth in retsina samples, and the results were confirmed by HPLC. Statistical analysis of these data showed that the results of the two methods compared favorably. This work provides a simple and easy approach to the determination of amaranth in foods with high sensitivity and excellent selectivity.