Development of Colorimetric Sensor Array for Instant Determination of Sodium Metabisulfite in Dried Longan

Abstract

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. Sodium metabisulfite has been used as a pretreatment chemical to prevent the gradual discoloration and to slow down the spoilage process of dried longan. The excessive use of this sulfiting agent can result in allergic reactions, particularly for sulfite-sensitive people. In this research study, a colorimetric strip was fabricated to determine the concentration of sodium metabisulfite in dried longan. The detection was based on reactions of a series of colorimetric reagents including four different Fuchsine compounds and an Ellman’s regent. The maximum change of color was observed 3 min after the reactions. To perform a quantitative analysis, the image of the strip was captured using a commercial scanner, and it was converted into an RGB color model to be digitally analyzed by chemometrics. Using partial least square (PLS) regression, the calibration range (5.00–250.00 mg/kg) provided R2 and Q2 values of 0.994 and 0.908, respectively. The limits of detection and quantitation were 5.48 and 16.6 mg/kg, which were sensible for the detection of the sulfiting agent in dried longan samples. The developed colorimetric strip was applied to determine the concentration of metabisulfite in dried longan fruit purchased from local markets in Chiang Mai, Thailand. The results agreed well with the findings obtained from the standard reference method. The developed strip could be an alternative solution for rapid, simple, and low-cost detection of the sulfiting agent in dried agricultural products, where test results could be instantly obtained without the requirement of sophisticated analytical instruments.