Novel Potentiometric Sensors for the Determination of Cochineal Red A and its Application to Food Analysis

In this research the novel potentiometric sensors have been evaluated for the selective determination of Cochineal Red A (CRA) in colored food. PVC membrane (PME) and coated graphite electrode (CGE) have been prepared based on tetraphenylphosponium-CRA ion pair as the electro active substance. The electrodes reveal linear emf-pCRA responses over wide concentration ranges of (1.0×10-4-1.0×10-1 M with a slope -19.0 mV decade-1 for PME) and (1.0×10-6-1.0×10-1 M with a slope -20.2 mV decade-1 for CGE) and limits of detection of 7.8×10-5 for PME and 8.0×10-7 for CGE. The potentiometric responses were independent of the pH of the test solution in the pH range 4-7. The proposed electrodes showed very good selectivity over a wide variety interfering ions. Electrodes have been successfully applied to the determination of Cochineal Red A in food products by direct potentiometric method. The results were in good agreement with the value obtained by using the official method (HPLC measurements).