A modified supported bilayer/diblock polymer--working towards a tunable coating for capillary electrophoresis

Area of Science:

• Analytical Chemistry
• Separation Science
• Materials Science

Background:

• Previous protein separation methods utilized surfactant bilayer/diblock polymer coatings.
• Coatings were composed of dioctadecyldimethylammonium bromide (DODAB) and poly-oxyethylene (POE) 40 stearate.

Purpose of the Study:

• To develop an improved method for generating DODAB/POE stearate coatings.
• To achieve more predictable electroosmotic flow (EOF), enhanced coating stability, and greater separation efficiencies.
• To facilitate easier method development for protein separations.

Main Methods:

• A sequential preparation method involving flowing DODAB followed by POE stearate through the capillary.
• Varying POE chain lengths (8, 40, and 100 oxyethylene units) to tune EOF.
• Utilizing mixtures of POE 8 and POE 40 stearate for continuous EOF variation.

Main Results:

• Tunable EOF achieved, ranging from -2.40 to -0.17 x 10⁻⁴ cm²/Vs.
• Separation efficiencies of 760,000-940,000 plates/m for basic proteins.
• Sequentially prepared coatings demonstrated superior stability (%RSD: 0.7-1.0% over 30 runs) compared to mixed methods (%RSD: 2.4-4.6% over 14 runs).
• Successful separation of histone proteins and acidic proteins.

Conclusions:

• The sequential preparation method offers significant advantages over the previous mixed method.
• Tunable EOF is crucial for maximizing resolution of proteins with similar mobilities.
• The improved coatings enable high-efficiency and stable separations of complex protein mixtures.