The invention relates to a method and associated apparatuses (100) for the detection of magnetic particles (MP) in a sample chamber (111). The method comprises the determination of a “particle-parameter” that is related to the amount of magnetic particles (MP) in a first detection region (P, C), the determination of a “cluster-parameter” that is related to the degree of clustering of magnetic particles (MP) in a second detection region (P, C), and the evaluation of the particle-parameter based on the cluster-parameter. Various apparatuses are disclosed that can be applied in said method. In one apparatus (100), a magnetic field (B) is generated in the sample chamber (111) in such a way that it has different inclinations in a first and second field region (P, C) and/or that it is oblique to the binding surface (112) in at least one field region. Magnetic particles (MP) are then detected in said first and second field region and/or in said at least one field region before and after a permanent switch-off of the inclined magnetic field. The resulting detection signals are related to each other to determine a cluster-parameter. In other embodiments, a cluster-parameter may be determined from light transmission measurements during the application of a magnetic field that is switched on and off.