A new screening electrochemical assay for field monitoring of food additive E120

Abstract

For field monitoring of food additive E120 concentration levels in foods, a simple, reliable, and inexpensive screening electrochemical method has been developed that based on direct drop casting of 50 μL sample onto the surface of a commercially available screen-printed voltammetric sensor and subsequent anodic oxidation of the carminic acid present using squarewave voltammetry. Before each screening analysis, it is necessary to determine the pH of the target sample at least with indicator paper due to the statistically significant influence of pH on the current yields of the respective electrode reaction. The peak area response obtained could be calibrated within a linear range 1–50 mg per 100 mL−1 carminic acid characterised with coefficient of determination >0.9930, a sensitivity of 2.181, 3.225, and 8.910 μAVmg−1L at pH 4, 3 and 2, respectively, and a detection limit of 2 mg L−1 carminic acid. Time-consuming optimization with a detailed interference study using a model lemonade, composited from a variety of possible ingredients and eventual contaminants, had to be included, which led to a significant simplification of the entire analytical procedure. Practical applicability of the developed screening electrochemical assay in the food safety control was successfully verified in analysis of candies, soft drinks, and alcoholic beverages. The determined E120 contents were in a good accordance with those obtained by the reference colorimetric method.