The invention relates to a method for quantitatively determining biological analytes in an aqueous solution in the presence of one or more functionalised surfaces, wherein the aqueous solution comprises at least one type of biological analyte and at least one type of fluorescence marker, characterised in that the quantity and/or concentration of the biological analyte or analytes is determined by measuring the fluorescence emission of the unbound fluorescence markers, as well as to a devices for carrying out said method.