A prototype of a low-cost and easy-to-use thin layer coulometric microfluidic device based on an ion-selective membrane for calcium detection is described. The microfluidic device was fabricated and consequently assembled with inexpensive materials without using sophisticated and centralized fabrication laboratory facilities. The linear range of the device is found to be 10–100 μM for a 60 s current integration time. Preliminary validations showed that the microfluidic device is suitable for the quantification of calcium in mineral water.