Abstract: An apparatus for the qualitative and/or quantitative measurement of analytes, in particular in biological samples by means of receptor ligand binding and having a magnetizing device for the production of a magnetic field at the location of the sample and with a detection device for measurement of magnetic properties of the sample is characterized in that the magnetizing device is spatially disposed with respect to the detection device in such a fashion that the magnetic field produced by the magnetization device at the location of the magnetization is attenuated by at least a factor of 10, and preferentially by a factor of 1000 or more, at the location occupied by the sample during the measurement, or in that a switching device is provided for which, throughout a predetermined time duration and in particular during the measurement phase of the detection device can switch-off the magnetic field of the magnetizing device at the location of the sample.