Silicate ions (SiO32-), or ionic silica, are known to cause silica scaling in industrial water applications when excess amounts are present; hence, concentrations must be monitored and kept at a constant low level. Ionic silica is conventionally measured by spectrophotometry in the form of its silicomolybdic complex based on the molybdenum blue reaction, but the operation process is complicated and not suitable for on-site detection. To solve these issues, microfluidic paper-based analytical devices (µPADs) have been gaining attention as portable, low-cost analytical devices suitable for on-site detection. The foldable origami type device described in this work enabled silica detection based on the molybdenum blue reaction, in the range of 50-1000 mg/L, with a practically detectable lowest concentration of 50 mg/L. The device showed selectivity for silicate ions and stability over 21 days when stored at 4 °C. The semi-quantitative analytical performance makes the proposed paper-based device attractive for on-site industrial monitoring.
Keywords: Industrial water analysis; Microfluidics; Molybdenum blue reaction; Paper-based devices; Silicate ion.
© 2023. The Author(s), under exclusive licence to The Japan Society for Analytical Chemistry.