Conventional biosensors , such as those based on surface plasmon resonance, lack spectral resolution and employ a permanent sensing layer that needs to be activated and also regenerated after use. In contrast, scanning of the UV/VIS spectrum of agarose beads, trapped in a specially designed flow cell, allows real time monitoring of labeled and unlabeled biomolecules, with spectral resolution, on a surface that can be automatically renewed, by microfluidic manipulation. Agarose beads are identical with column materials used in affinity chromatography and therefore are readily available, derivatized with a wide choice of bioligands. In this way, flow injection absorptiometry on renewable surfaces provides a basis for a new class of biosensors with ‘open architecture’ that allows the development of novel types of immunoassays employing both unlabeled and labeled molecules. The method also has interesting implications for affinity chromatography, because it uses identical materials and investigates the same type of bioligand interactions. An improved configuration of the jet ring cell is introduced and it is shown that both large (IgG) and small molecules (biotin) can be detected down to the 25 ng level reproducibly and rapidly.