Isoelectric Point (IEP)

Isoelectric Point

The isoelectric point (IEP) of a dispersion is the pH value where the zeta potential equals zero. This is the condition that is least stable and frequently leads to agglomeration for suspensions and phase separation for emulsions. Determining the IEP is a common zeta potential application for the Nicomp DLS particle size and zeta potential analyzer.

PSS Isoelectric Point (IEP)
 

Read the sections below for additional information on this application.

Isoelectric Point (IEP) of Proteins

With the Nicomp 380 ZLS it is possible to not only size proteins but also determine their isoelectric point (IEP). Ampules of bovine serum albumin (BSA) were purchased from Sigma Aldrich and diluted 1:100 with deionized water. Figure A below shows the volume-weighted mean particle diameter to be 5.5 nm. Aggregates of ~25nm were also detected. For…

Isoelectric Point (IEP) Test

              Zeta potential is a measure of the charge on the surface of a particle. The zeta potential is a function of the specific surface chemistry of a dispersion and is affected by changes in pH, salt and surfactant concentration. The isoelectric point (IEP) is the pH value at…

Isoelectric Point (IEP) of Coffee-mate

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…