A novel, cost-effective platform using a biodegradable sensor and a simple heat control unit was proposed for multi-sample formaldehyde (FA) assay in one run based on pervaporation. The biodegradable sensor was a composite starch gel attached to paper and immobilized with a mixture of color agents of modified 4-amino-3-hydrazino-5-mercapto-1,2,4-triazol (AHMT). The sensor was situated on the cap of a vial that served for pervaporation. Two types of heat control units were specially designed using the concepts of aluminum block and water bath heating. With these two designs, multi-sample assays together with standard calibration could be performed in the same run under the same conditions. An FA solution was placed in the vial of the pervaporation unit. After a heating period, FA vapor would change the color of the sensor to purple due to the reaction between AHMT and FA. As a result, the color intensity was proportional to the FA concentration. The change of the color (green or G intensity) was monitored using a smartphone camera and image processing software. Factors affecting the sensitivity of the assay, pervaporation time, pervaporation temperature, FA solution volume, and humidity, were studied. Under the chosen condition, the developed procedure, with a calibration of G intensity = 7.93[FA] + 198, R2 = 0.98, was applied to analyze real samples of seafood and mushrooms available in local markets in Thailand. As there were 24 pervaporation units in the proposed platform, 5 working standards and 9 samples with duplicates could be included in a 1-run assay either in the laboratory or on-site. The developed assay offers green chemical analysis with a simple, cost-effective approach. This serves the UN-SDGs of #2, #3, #7, #10, and #12.
Keywords: Bio-degradable sensor; Formaldehyde; Green chemical analysis; Image processing; Pervaporation; UN-SDGs.
© 2022. The Author(s), under exclusive licence to The Japan Society for Analytical Chemistry.