A continuous-flow biochemical detection system is presented which allows the use of solid-phase immobilised affinity proteins. The biochemical detection is performed by mixing analyte with a labelled ligand followed by the addition of solid-phase immobilised affinity protein. After a reaction time of 85 s, free and bound label are separated by means of a hollow fibre module. Quantitation of the free label is performed with a conventional flow-through fluorescence detector. Total assay time amounts to less than 2 min. Biotin was chosen as the model compound using a range of streptavidin-coated solid-phases and an antibody-coated solid-phase as affinity material, and fluorescein–biotin as low-molecular-mass label. The relative standard deviation for twenty repetitive injections was 10.9%. A calibration curve was constructed in the concentration range between 20 and 400 nmol l⁻¹ leading to a correlation coefficient of 0.994. A limit of detection of 8 nmol l⁻¹ was obtained. © 1997 Elsevier Science B.V.