The invention relates to a method and a biosensor system (300) for the detection of target components (TC) in a biological sample. In a preferred embodiment, magnetic purification particles (PP) are added to the sample that can bind interfering components (IC) (if present) which interfere with the detection process. The purification particles (PP) with bound interfering components (IC) may be removed from the sample and transferred through a magneto-capillary valve (MCV1) into a waste chamber (320).