Hybrid Microfluidic-Flow Injection System for Determining Copper(II) in Aqueous Solution by Homemade Microfluidic-Chip

Background: A new technique was designed for determining copper in an aqueous solution. Copper was determined by a hybrid system microfluidic coupled with flow injection. The homemade microfluidic chip (MFC) is used for injecting copper and 2,9-Dimethyl-1,10-phenanthroline (2,9 DMP) reagent as a merging zone technique, whereas uric acid is used as a reducing agent and carrier. Methods: A microfluidic chip was made by a Computer Numerical Control (CNC) laser machine using the AutoCAD application for the study of copper by the hybrid system. The chip contains two microchannels with a volume of 60 μL for copper(II) and 2,9 DMP reagent. As a carrier solution and reducing agent, 40 mg/L of uric acid was pumped at a flow rate of 5.2 mL/min. Conditions of the coupled technique and analyses were measured at 454 nm. Results: This system's approach has a linear range, a detection limit (S/N = 3), and a quantitation limit (S/N = 10) at 0.1-25 mg/L (r² 0.9979), 0.03 and 0.09 mg/L, respectively. Also, there was a repeatability of analyses (n = 7) with an average RSD of 0.97 % for concentrations of 5, 10, and 20 mg/L. The dispersion coefficients were 1.977, 1.789, and 1.555 for the three concentrations 5,10, and 20 mg/L, respectively. The recovery of copper in the aqueous solution was estimated to be 103.5%. Dead volume and throughput were zero and 62 per hour, respectively. Sandell’s sensitivity and molar absorptivity were 2.467×10^-3 μg/cm² and 1.947×10⁵ L/mol cm, respectively. Conclusion: The analysis in the novel hybrid microfluidic-flow injection system is efficient, simple, and fast, and it can be used to determine the concentration of copper in an aqueous solution. The homemade microfluidic chip is a low-cost component that uses only an small volume of copper and reagent during analysis.