Capillary electrophoresis has been used to characterize samples of the copolymeric anionic polysaccharides homo and rhanino-galacturonan (HG and RGI, respectively). In the case of HG, the ratios of the two component sugar residues, galacturonic acid and its methylesterified analogue, have been controlled chemically to produce samples comprised of varying degrees of methylesterification (DM). The mapping of the measured electrophoretic mobilities to the biopolymer charge density has been considered in some detail and for HG substrates with random intramolecular patterns of methylesterification it is shown that the experimentally extracted intermolecular DM distribution agrees well with the predictions of calculations based on the binomial theorem. This demonstrates that the intermolecular distribution of the methylesterification of pectin samples contains information on the intramolecular pattern by virtue of the fact that they are both manifestations of the same statistical process.