A portable and stable dry starch-KI sensor for headspace iodine vapor detection: A green approach for sensitive ascorbic acid quantification in colored juices

Abstract

This study introduces a stable and portable dry starch-KI paper sensor for detecting iodine vapor in the headspace of a microwell plate, enabling sensitive quantification of ascorbic acid (AA) in colored fruit and vegetable juices. The method leverages the reaction between AA and potassium iodate (KIO3) to generate iodine vapor, producing a strong colorimetric response upon interaction with the starch-KI coating. The sensor maintains consistent color intensity for up to 90 min, ensuring reliable on-site analysis. Uniformity testing of 96-spot absorbance for 0.5 mM AA across three batches (n = 3) yielded a mean absorbance of 0.264 ± 0.016 with a %RSD of 6.1 %. Stability assessments at three AA concentrations produced %RSD values of 9.4 %, 5.0 %, and 5.1 %, respectively. The microwell plate format facilitates rapid analysis with minimal sample preparation, effectively minimizing interference from juice color and matrix effects. The sensor demonstrated a linear detection range of 0.1–0.75 mM (r2 = 0.9942) with an LOD of 0.05 mM. Application to fresh juice samples yielded a %recovery of 80–120 % (n = 13). This approach addresses critical challenges such as stability, portability, and matrix interference by effectively separating analytical signals from juice pigments. With a high AGREE score of 0.7, reflecting strong alignment with green analytical chemistry principles, this innovative method offers a practical, eco-friendly solution for on-site AA quantification in nutritional analysis.