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Updated: Aug 11, 2026

Capillary Electrophoresis Separation of Monoclonal Antibody Isoforms Using a Neutral Capillary
Published on: January 16, 2017
Isoelectric focusing of monoclonal antibodies by capillary electrophoresis
The isoelectric points (pIs) of murine monoclonal antibodies (MAbs) determined by published one-step capillary isoelectric focusing (CIEF) methods using simultaneous focusing and electroosmotic mobilization showed appreciable deviation from the pI values determined by the slab gel electrophoretic method. The present report describes a modified one-step CIEF method that accurately determines the pIs of MAbs. The modifications include use of internal standards with pIs below and above the pI ranges of MAbs and calculation of pIs from a fitted nonlinear standard curve. Proteins with pIs in the same range as MAbs were first used to establish the efficacy of the method. The present CIEF procedure is highly reproducible and easy to perform for MAbs.
The isoelectric points (pIs) of murine monoclonal antibodies (MAbs) determined by published one-step capillary isoelectric focusing (CIEF) methods using simultaneous focusing and electroosmotic mobilization showed appreciable deviation from the pI values determined by the slab gel electrophoretic method. The present report describes a modified one-step CIEF method that accurately determines the pIs of MAbs. The modifications include use of internal standards with pIs below and above the pI ranges of MAbs and calculation of pIs from a fitted nonlinear standard curve. Proteins with pIs in the same range as MAbs were first used to establish the efficacy of the method. The present CIEF procedure is highly reproducible and easy to perform for MAbs.
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