Accurate, affordable, and easy electrochemical detection of ascorbic acid in fresh fruit juices and pharmaceutical samples using an electroactive gelatin sulfonamide.

In this study, we demonstrated how to design and construct a highly specific and sensitive sensor capable of rapidly and accurately detecting ascorbic acid (AA). A sulfonamide derivative (S) acting as a novel monomer was synthesized through an aldol condensation reaction. Subsequently, a free radical-mediated grafting polymerization approach was used to create a new generation of gelatin (Gel) grafted with poly sulfonamide derivative (Gel-g-PS). The graft percentage (GP%) was 60 ± 0.5% with a conversion rate of 98.3%. Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were utilized to confirm the formation of Gel-g-PS. The developed gelatin sulfonamide modified screen printed electrode (Gel-g-PS/SPE) was employed for the determination of ascorbic acid (AA) in fruit juices and pharmaceutical samples. Gel-g-PS/SPE showed excellent electrochemical catalytic activities toward AA oxidation compared to bare (unmodified) SPE. Ascorbic acid displayed a sensitive oxidation peak at 0.35 V using the differential pulse voltammetry technique. Under optimized experimental conditions, the two linear ranges for AA detection were obtained to be from 0.2-5 ppb and 20-600 ppb, with a limit of detection (LoD) of 0.03 ppb and a limit of quantification (LoQ) of 0.11 ppb. The proposed Gel-g-PS modified SPE surface demonstrated good selectivity, stability, reproducibility, and repeatability as well as a good recovery rate in fresh fruit juices and pharmaceutical samples.