Mobility distribution of synthetic and natural polyelectrolytes with capillary zone electrophoresis

Parameters are proposed to describe the distribution of the effective elect rophoretic mobilities of various anionic polyelectrolytes such as poly(styr ene-4-sulfonates) and humic substances of different origins analyzed by cap illary zone electrophoresis, The first step of the data treatment is a base line correction and conversion of the electrophoretic raw time data to effe ctive electrophoretic mobilities (mu-scale), taking into account the electr oosmotic flow. With this new mu-scaling, the electropherograms are more rep resentative of velocity-based separation phenomena than those using migrati on times, and a direct comparison of electropherograms is possible. Four di fferent average electrophoretic mobilities were defined: the number-average effective mobility (mu(n)), the weight-average effective mobility (mu(w)), the z-average effective mobility (mu(z)), and the peak-average electrophor etic mobility (mu(p)). The polydispersity of the mobility of mixtures was d escribed by the mu(w)/mu(n), mu(z)/mu(w) and mu(p)/mu(w) ratios. These para meters were used to describe the electrophoretic mobility distributions of different fractions of restricted molecular size: those obtained by ultrafi ltration from a soil humic acid at neutral pH and reference humic substance s of the International Humic Substances Society at different values of pH a nd ionic strength. The data clearly show the influence of both molecular si ze and charge distribution of the analyzed mixtures on the mobility distrib utions.