PDMS Chip-Based Sequential Injection Analysis System With Integrated Pneumatic-activated Valves

Flow injection analysis (FIA) is automated technique for sample pre-treatment, which has advantages of high throughput and precision, and low consumption of samples and reagents (microliter scale). Sequential injection analysis (SIA), as the second generation of FIA, has some special advantages, namely, the system hardware is simple and reliable, the operation is easy to implement under control of computer. However, the sample and reagents are introduced into the same channel sequentially in most sequential injection analysis systems, which is easy to induce cross-contamination.In this work, a SIA system based on PDMS microfluidic chip with integrated pneumatic-activated valves was developed. The SIA operation was achieved by switching the microvalves under control of computer program without the need of conventional syringe pump and selective valve. Using this device, the introduction of sample and reagents was simultaneously performed to form a multi-phase laminar flows, to avoid the cross-contamination between different liquids. This method provide a novel operation mode for SIA systems. The present system has advantages of low consumption for sample and reagents (picoliter scale), high integrity and automation, ease of operation. Various factors affected the mixing of sample and reagents were investigated. The present system was successfully applied in enzyme inhibition assay.