DESIGN OF A MICROFLUIDIC DEVICE FOR COLORIMETRIC ESTIMATION OF SOIL PH USING AN OPTIMIZED INDICATOR MIXTURE
H.M.C.S.Wijerathne1, N.D. Tissera2, G. Priyadarshana3 and R.N.Wijesena4*
1Faculty of Graduate Studies, University of Sri Jayewardenepura, Nugegoda, Sri Lanka, 1,3Department of Materials and Mechanical Technology, Faculty of Technology, University of Sri Jayewardenepura, Homagama, Sri Lanka, 1Department of Limnology and Water Technology, Faculty of Fisheries and Marine Sciences and Technology, University of Ruhuna, Matara, Sri Lanka, 4Department of Textile and Clothing Engineering, Institute of Technology, University of Moratuwa, Homagama, Sri Lanka
Session: Technical Session A
Abstract
Soil pH is a critical parameter in soil analysis, influencing nutrient availability, microbial activity, and overall soil health. Although several methods exist for measuring soil pH, many of them face limitations in terms of continuous monitoring, including the need for laboratory infrastructure, trained personnel, or expensive instrumentation. Consequently, there is a growing need to develop novel approaches that are rapid, low-cost, userfriendly, and suitable for on-site applications. In this study, a colorimetric detection method was developed using an optimized mixture of pH indicators integrated into a microfluidic device (MFD) for the determination of soil pH. This approach enables farmers and field workers to directly assess soil pH in the field across a broad range of pH values (2–10). The indicator mixture, consisting of bromocresol green, bromothymol blue, bromophenol blue, phenol red, and thymol blue, was designed to produce distinct colour transitions over a wide pH spectrum. A linear and visually discernible response was achieved across two key pH intervals: an acidic range from pH 2.0 to 6.0 (covering 4.0 pH units) and an alkaline range from pH 7.0 to 12.0 (covering 5.0 pH units), demonstrating the suitability of the method for practical soil monitoring applications.
Keywords: colorimetry, indicator- mixture, microfluidic technologies, soil pH
DOI: 10.64752/XZPE9592