Copolymerized Micelles as Pseuodophases in Micellar Electrokinetic Chromatography

Fayetteville State University, Fayetteville NC

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Abstract

The use of CE for analytical separations has many advantages over the other two commonly used[unreadable] chromatographic techniques, that is, gas chromatography and liquid chromatography. Some of these[unreadable] advantages include lower operating costs, much higher separation efficiency, small sample size required,[unreadable] short analysis time, versatility, and simplicity. Micellar electrokinetic chromatography (MEKC) was introduced[unreadable] in 1984 and is the CE mode most commonly used for enantiomeric separation. While MEKC is a very useful[unreadable] technique, it has several disadvantages. One disadvantage is that in order for the surfactant to be effective[unreadable] as a pseudostationary phase, it must be at a concentration above its CMC. In addition, the dynamic[unreadable] equilibrium between the free surfactant molecules and the micelle can lead to a decrease in separation[unreadable] efficiency as compared to a more ordered micellar system. To overcome these drawbacks, polymeric[unreadable] surfactants (or molecular micelles) were introduced. First advantage of molecular micelles is the elimination[unreadable] of the dynamic equilibrium between monomer and the micelle. Second advantage is the lack of a CMC, thus[unreadable] they may be used at concentrations well below the CMC of the unpolymerized surfactants. Single amino[unreadable] acid-based polymeric surfactants as chiral selectors for MEKC were first introduced in 1994. A major[unreadable] advantage of this approach is that different functionalities, such as a variety of chiral head groups (e.g.,[unreadable] amino acids), can be integrated into the polymeric surfactants. This introduces an effective way of[unreadable] manipulating selectivity of the pseudostationary phase. In addition, the availability of both D and L optical[unreadable] configurations of amino acid-based pseudostationary phases is particularly advantageous to more accurately[unreadable] determine enantiomeric impurities by reversal of the migration order of the two enantiomers. The main[unreadable] disadvantage of these types of molecular micelles is that they are not soluble below pH 7.0 due to[unreadable] carboxylated head groups (e.g., amino acids). The PI intends to develop a new class of amino acid based[unreadable] polymeric surfactants that could be used at wider pH ranges. Highly soluble sulfated achiral surfactants and[unreadable] amino acid basid chiral surfactants will be copolymerized at various molar ratios to form novel copolymerized[unreadable] molecular micelles. These surfactants will be characterized using a variety of analytical methods and will be[unreadable] applied as pseudostationary phases in MEKC for separation of chiral molecules at a wider pH range.