The microfluidic device consists of filter paper strips and SPCE, which enables direct electrochemical detection of heavy metals. When the sample solution flows along the filter paper and across the surface of SPCE, it provides a thin mechanically stabilized film of water or other fluids on the surface of SPCE and delivers fresh sample for analysis. This feature of the device allows the original samples of gas dissolved and physically contaminated water to be directly applied for electrochemical measurements.