Exploiting an automated microfluidic hydrodynamic sequential injection system for determination of phosphate

Abstract

© 2017 Elsevier B.V. A microfluidic hydrodynamic sequential injection (μHSI) spectrophotometric system was designed and fabricated. The system was built by laser engraving a manifold pattern on an acrylic block and sealing with another flat acrylic plate to form a microfluidic channel platform. The platform was incorporated with small solenoid valves to obtain a portable setup for programmable control of the liquid flow into the channel according to the HSI principle. The system was demonstrated for the determination of phosphate using a molybdenum blue method. An ascorbic acid, standard or sample, and acidic molybdate solutions were sequentially aspirated to fill the channel forming a stack zone before flowing to the detector. Under the optimum condition, a linear calibration graph in the range of 0.1–6 mg P L−1was obtained. The detection limit was 0.1 mg L−1. The system is compact (5.0 mm thick, 80 mm wide × 140 mm long), durable, portable, cost-effective, and consumes little amount of chemicals (83 μL each of molybdate and ascorbic acid, 133 μL of the sample solution and 1.7 mL of water carrier/run). It was applied for the determination of phosphate content in extracted soil samples. The percent recoveries of the analysis were obtained in the range of 91.2–107.3. The results obtained agreed well with those of the batch spectrophotometric method.