A Simple Low-Cost Paper-Based Analytical Device For Detecting Water Hardness

High water hardness can cause damage to piping systems and negatively impact health. This study aimed to develop a simple, low-cost, and user-friendly paper-based analytical device to detect water hardness levels in the field. The device was developed using a complexation reaction principle with specific reagents, namely a pH 10 buffer solution and Eriochrome Black T (EBT) indicator, immobilized on Whatman filter paper. The test results demonstrated that the test strip can optimally detect water hardness within a concentration range of 50 ppm to 350 ppm. The device also exhibited good sensitivity, accuracy, and repeatability. In conclusion, this test strip offers a practical, rapid, and portable analytical alternative without the need for complex instruments or special skills, making it highly applicable for on-site water quality monitoring.