COLLABORATIVE STUDIES OF ZETA-POTENTIAL MEASUREMENTS AND ELECTROPHORETIC MEASUREMENTS USING REFERENCE SAMPLE

Simultaneous measurements of zeta-potential for two standard latex sus pensions were carried out so as to assess the reliability of each of t hese measurement techniques and find means for their improvement. Furt hermore, syntheses of a reference particle dispersion stabilized steri cally in an aqueous medium without any electrostatic effects and measu rements of zeta-potential using the reference dispersion as a standard were performed under various experimental conditions. It became appar ent that the dense adsorption layer of hydroxypropylcellulose (HPC), w ith a lower critical solution temperature (LCST), formed on latex part icles with a low surface charge density at temperatures higher than th e LCST, plays a role in completely shielding the electrostatic effect arising from the surface charge on the bare particles. Such reference particles with zero zeta-potential allow us to determine the.electroph oretic mobility of unknown samples at the one-half depth in the electr ophoretic cell by subtracting the mobility of the reference sample at the same level. Furthermore, the zeta-potential of the cell wall can b e easily determined from the mobility of the reference sample, because the apparent velocity profile of the reference sample indicates the l iquid flow velocity in the cell. (C) 1998 Elsevier Science B.V. All ri ghts reserved.