Methods for preparing a dilution series for use in forming calibration curves, preferably in the field of surface plasmon resonance, are provided. In one example, a dilution series is prepared by using receptacles such as tubes of a micro well plate in which samples of the dilution series are mixed. In another example, a dilution series is prepared by using a convection mix in a receptacle for achieving a concentration gradient in the sample. A biosensor system arranged to perform steps of methods disclosed are provided. A data processing apparatus and a software for performing steps of methods disclosed, and a computer readable medium for storing the software are also provided.