PAPER-BASED DEVICE FOR WATER ANALYSIS

Abstract

A novel paper-based analytical device has been developed to simultaneously determine water hardness, chloride, and iron in real water samples with radial distance-based measurement. Water hardness was detected using Eriochrome Black T (EBT) assay. Chloride was detected based on the reverse-Mohr precipitation titration. Iron was detected using bathophenanthroline (Bphen). The circular device is divided into three zones, facilitating readings based on radial distances for the three assays at the same time. Specific reagents coating on the detection zone for individual analyte detection was carried out using optimal condition. Water samples were analyzed by adding 75 μL of standard/sample solution to the inlet. As the water sample flows into the sample inlet and diffuses radially outward, the analyte reacts with the reagents, producing a colored band whose radial distance is proportional to the analyte concentration in the water sample. After 3 minutes, the radial distance can be simply measured using either a ruler or ImageJ program to quantify water hardness, chloride, and iron in water. The developed method gave limit of detection for total hardness, chloride and iron of 13 mg/L CaCO3, 0.25 mM and 0.5 mg/L, respectively. The linear range obtained from total hardness, chloride and iron detections were 25-1501 mg/L CaCO3, 1-100 mM and 0.5-300 mg/L, respectively. The sensor demonstrates high selectivity for simultaneous detection of water hardness, chloride, and iron in various water samples with good agreement with traditional standard methods indicating high accuracy and could be potentially used as on-site water quality assessment in the future.

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