การพัฒนาเซ็นเซอร์ชนิดตรวจวัดสีสำหรับคลอรีนในน้ำ โดยใช้เทคนิควิเคราะห์ภาพดิจิทัล

Abstract

In this work, a green colorimetric sensor was successfully developed for free chlorine determination with the portability for on-site detection. It was prepared from the cross-linkage of natural materials, which were tapioca starch (TAS) and agar (AG). The hybrid biopolymer was employed to entrap N, N-diethyl-p-phenylenediamine (DPD) as chromogenic species and it was coated on the lid of plastic micro-PCR tube. The colorimetric determination was based on the reaction between DPD reagent and free chlorine in sample. The intensity of color product was measured by using a smartphone and reported as Red-Green-Blue (RGB) intensity. The optimum condition for the sensor film synthesis was studied and it was found at 2.0 g DPD/10 mL solution, 0.16 g EDTA in 10 mL phosphate buffer, and 0.5: 1 of the volume ratio between buffer and DPD solution. The biofilm was completely polymerized by using the incubation at of 60 °C and 605 minutes to obtain the best film performance with a fast analysis of 1 min reaction time. By the combination with digital image analysis, semi-quantitative analysis could be obtained via the establishment of calibration graph showing the relationship between intensity or absorption RGB and free chlorine concentration. The developed method presented the great performances of wide linear range (0.3-15 mg/L), low detection limit (0.26$0.00 mg/L), good accuracy (0.31-10.10% relative error) high precision (0.83-3.98 %RSD) and the excellent sensitivity of 8.6t0.2 a.u/(mgL*) for chlorine determination. When the proposed sensors was applied with the different kind of real water sample, ie. the tap water, swimming pool water, drinking water and sea water, it showed the comparable results of less than 10% difference with the standard spectrophotometric method. This indicated the high potential of developed film as the powerful technique for free chlorine analysis