All our products are been tested by a tiered-process of quality control. Standard quality control of all our beads consists of gravimetric concentration measurements. In addition, particle concentration and size-distribution are measured with the AccuSizer 780 (Optical Particle Sizer, PSS NiComp Particle Sizing System) for all unmodified silica beads, using appropriate standards in order to avoid material dependency. For quality control of surface-modified beads, MagnaMedics has developed in-house assays to evaluate and quantify our beads for specific as well as non-specific interactions in commonly used applications.