A method for determining the kinetic parameters of a reaction between an analyte and ligands which are attached to a test surface of a flow cell, the method comprising the steps of, (a) flowing a first volume of sample fluid (V1), which contains said analyte, over the test surface, between a first point in time (t 1 ) to a second point in time (t 2 ); (b) flowing a first volume of buffer fluid (Vb1), which is without analyte, over the test surface, between a third point in time (t 3 ) to a fourth point in time (t 4 ); (c) flowing at least a second volume of sample fluid (V2), which contains said analyte, over the test surface, between a fifth point in time (t 5 ) to a sixth point in time (t 6 ); (d) flowing at least a second volume of buffer fluid (Vb2), which is without analyte, over the test surface, between a seventh point in time (t 7 ) to a eight point in time (t 8 ); (e) using a sensor to measure the binding of analyte to ligands on the test surface to obtain a binding curve; (f) using only the parts of the binding curve which are in predefined interval time periods, without using the other parts of the binding curve, to determine the kinetic parameters, wherein the predefined interval time periods comprise a first and second interval time periods (t1Δ, t2Δ), and wherein the first interval time period (t1Δ) occurs between the second point in time (tz) and fifth point in time (t 5 ); and wherein the second interval time periods (t2Δ) occurs between the sixth point in time (t 6 ) and a ninth point in time (t 9 ) wherein the ninth point in time (t 9 ) occurs sometime after the eight point in time (t 8 ), or, the ninth point in time (t 9 ) is equal to the eight point in time (t 8 ). (a) flowing a first volume of sample fluid (V1), which contains said analyte, over the test surface, between a first point in time (t 1 ) to a second point in time (t 2 ); (b) flowing a first volume of buffer fluid (Vb1), which is without analyte, over the test surface, between a third point in time (t 3 ) to a fourth point in time (t 4 ); (c) flowing at least a second volume of sample fluid (V2), which contains said analyte, over the test surface, between a fifth point in time (t 5 ) to a sixth point in time (t 6 ); (d) flowing at least a second volume of buffer fluid (Vb2), which is without analyte, over the test surface, between a seventh point in time (t 7 ) to a eight point in time (t 8 ); (e) using a sensor to measure the binding of analyte to ligands on the test surface to obtain a binding curve; (f) using only the parts of the binding curve which are in predefined interval time periods, without using the other parts of the binding curve, to determine the kinetic parameters, wherein the predefined interval time periods comprise a first and second interval time periods (t1Δ, t2Δ), and wherein the first interval time period (t1Δ) occurs between the second point in time (tz) and fifth point in time (t 5 ); and wherein the second interval time periods (t2Δ) occurs between the sixth point in time (t 6 ) and a ninth point in time (t 9 ) wherein the ninth point in time (t 9 ) occurs sometime after the eight point in time (t 8 ), or, the ninth point in time (t 9 ) is equal to the eight point in time (t 8 ). <EOS>