Electrochemical detection of Sudan I by using an expanded graphite paste electrode

A sensitive and convenient method was developed for the electrochemical determination of Sudan I by using an expanded graphite paste electrode (EGPE). The EGPE was prepared by mixing expanded graphite (EG) with solid paraffin at a mass ratio of 97:3. Due to the multiporous structure and large specific surface area of the EG, the EGPE showed high electrocatalytic activity toward the oxidation of Sudan I. Under optimal experimental conditions, the EGPE exhibited a wide linear response to Sudan I ranging from 5 × 10−9 to 7.0 × 10−6 M with a high sensitivity of 32.33 A M−1 cm−2 and a low detection limit down to 0.9 nM (S/N = 3). This method showed good accuracy, acceptable precision and reproducibility. The assay results of Sudan I in ketchup and chilli sauce samples obtained by the proposed method were in a good agreement with the reference values detected by HPLC. The proposed method provided a useful tool for the assay of Sudan I in food samples.