What is the difference between surface titer and parking area, and how are values determined?
The ‘surface titer’ value speaks to the level of functionalization for a defined mass of functionalized microspheres. Surface titer values are available for many, but not all, lots of functionalized microspheres. In some instances, when material was not titrated, theoretical surface titer values may be available. We report surface titer values in whole numbers as microequivalents per gram microspheres (µeq/g). NOTE: µeq/g is equal to micromole/gram. • Polymeric/COOH: Surface titer is determined by conductometric (usual) or potentiometric titration. • Polymeric/NH2: Amino-functionalized microspheres are often not titrated, due to concerns regarding reliability of the resultant data, i.e. it is believed that H+ ions penetrate the surface, or ‘fuzzy layer,’ of the microsphere, resulting in titration of functional groups that are not truly available for covalent coupling reactions. When performed, ‘titration’ is typically accomplished through a ninhydrin or other colorimetric assay for det
