pH-dependent surface charging and points of zero charge. IV. Update and new approach.

The recently published points of zero charge (PZC) and isoelectric points (IEPs) of various materials are compiled to update the previous compilation [M. Kosmulski, Surface Charging and Points of Zero Charge, CRC Press, Boca Raton, FL, 2009]. Unlike in previous compilations by the same author [Chemical Properties of Material Surfaces, Dekker, New York, 2001; J. Colloid Interface Sci. 253 (2002) 77; J. Colloid Interface Sci. 275 (2004) 214; J. Colloid Interface Sci. 298 (2006) 730], the materials are sorted not only by the chemical formula, but also by specific product, that is, by brand name (commercially available materials), and by recipe (home-synthesized materials). This new approach indicated that the relatively consistent PZC/IEP reported in the literature for materials having the same chemical formula are due to biased choice of specimens to be studied. Specimens which have PZC/IEP close to the "recommended" value are selected more often than other specimens (PZC/IEP not reported before or PZC/IEP reported, but different from the "recommended" value). Thus, the previously published PZC/IEP act as a self-fulfilling prophecy.