Mass Production and Outside Test of Microfluidic Paper Based Analysis Devices for Determining Chromium Ions in...

Hexavalent chromium ions in industrial wastewater can bring serious pollution to the environment and a variety of harms to human health. It is necessary to develop a novel technique to determine the heavy ions. In this work, we designed a special machine to enhance the production of microfluidic paper based analysis devices (μPADs, ∼1000 μPADs/h), which could be used to determine the industrial wastewater. We optimized the diphenyl carbamide solution and the volume of liquid to be tested. Finally, we established a fitting curve of the standard Cr concentration and color intensity from the μPADs. We carried out outside experiments in an industrial park, which needed a great amount of stable and repeatable devices for the test. In the concentration range of 250-600 mg/L, 74% of the measurement results had a relative error of less than 20%; in the concentration range of 50-250 mg/L, 72% of the measurement results had a relative error of less than 20%. Our results demonstrated that the accuracy and repeatability satisfied the requirements for wastewater detection, which could be extended to industrial application.