Seeking high-sensitivity flow injection analysis

The use of flow-injection systems for biotechnology assays is attrctive but the reduced sensitivity of such systems over their manual descrete-sample counterparts has limited their use. Model systems are studied to develop the concepts needed for the design of high-sensitivity flow-injection systems for the determination of macromolecules. Both open- and packed-tube systems were examined. Initial hydrodynamic studies were done with dye; then selected designs were tested for protein determinations based on a bromocresol green assay. The packed-bed systems provided better mixing, but dispersion was about the same as that of the open-tube systems and back-pressures were much higher. This work indicates that combinations of narrow (i.d. ⩽ 0.5 mm) and short (⩽ 10 cm) open tubes, small-volume flow cells (8 μl) and slow flow rates (⩽ 0.05 ml min-1) give better sensitivity.