Isoelectric Point (IEP) of Coffee-mate
The isoelectric point (IEP) is the pH value where the zeta potential is zero. The IEP can be determined by the Nicomp 380 ZLS by titrating the sample and recording zeta potential as a function of pH. Coffee-mate powder was prepared by mixing 0.1 g in 200 mL of DI water. The sample was placed on a magnetic stirring plate and mixed constantly during the study, with a newly calibrated pH probe immersed in the suspension. The pH was altered by adding drops of 0.1N hydrochloric acid. After the pH stabilized a sample was removed by a syringe and injected into the zeta potential cell. Three zeta potential measurements were performed and the average value were plotted vs pH. The results are shown in the graph below.
The IEP of the Coffee-mate suspension in this study was determined to be at pH 4.26.