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.

焦亚硫酸钠已被用作预处理化学品，以防止逐渐变色并减慢干龙眼的变质过程。过度使用该亚硫酸化剂会导致过敏反应，尤其是对亚硫酸盐敏感的人群。在这项研究中，制备了比色条，以确定干龙眼中焦亚硫酸钠的浓度。该检测基于一系列比色试剂的反应，包括四种不同的品红化合物和Ellman试剂。反应3分钟后观察到最大的颜色变化。为了进行定量分析，使用商用扫描仪捕获条带的图像，并将其转换为RGB颜色模型，以通过化学计量学进行数字分析。使用偏最小二乘（PLS）回归，R ²和Q ²值分别为0.994和0.908。检出限和定量限分别为5.48和16.6 mg / kg，对干龙眼样品中的亚硫酸化剂的检测是明智的。使用开发的比色条测定从泰国清迈当地市场购买的龙眼干果中偏亚硫酸氢盐的浓度。结果与从标准参考方法获得的结果非常吻合。所开发的试纸条可以作为快速，简单和低成本检测干燥农产品中亚硫酸盐化试剂的替代解决方案，无需复杂的分析仪器即可立即获得测试结果。