ASPECTS OF SAMPLE DISPERSION FOR OPTIMIZING FLOW-INJECTION ANALYSIS SYSTEMS

Solute dispersion of an injected sample plug was studied by using an experimental apparatus with ideal laminar flow in order to develop a hydrodynamic model for the design of sensitive and precise flow-injection analysis systems. The dispersion behaviour of the sample slug under different manifold conditions was first studied in detail to evaluate the effects of various operating conditions such as tube radius, tube length, flow-rate and molecular diffusion coefficient of sample solute. The capillary flow properties were also examined for some commercial micropumps to select the most suitable pumping method. Mixing profiles and baseline stability in short, straight tubes were investigated. A double-plunger micropump having a linear cam mechanism and a fast, short reciprocation time was proposed to obtain smoother mixing and more stable pumping with good reproducibility. Complete mixing and low flow-rate pumping are strongly desired for reliable flow-injection methods for industrial process use; biosensing devices for protein and enzyme bioassays require lower consumption of valuable reagents.