Polymeric Sulfated Amino Acid Surfactants: A Class of Versatile Chiral Selectors for Micellar Electrokinetic Chromatography (MEKC) and MEKC-MS
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- 作者：Syed Asad Ali Rizvi ; Jie Zheng ; Robert P. Apkarian ; Steven N. Dublin ; Shahab A. Shamsi
- 刊名：Analytical Chemistry
- 出版年：2007
- 出版时间：February 1, 2007
- 年：2007
- 卷：79
- 期：3
- 页码：879 - 898
- 全文大小：2192K
- 年卷期：v.79,no.3(February 1, 2007)
- ISSN：1520-6882
文摘
In this work, three amino acid-derived (L-leucinol, L-isoleucinol, L-valinol) sulfated chiral surfactants are synthesized and polymerized. These chiral sulfated surfactantsare thoroughly characterized to determine critical micelleconcentration, aggregation number, polarity, optical rotation, and partial specific volume. For the first time themorphological behavior of polymeric sulfated surfactantsis revealed using cryogenic high-resolution electron microscopy. The polysodium N-undecenoyl-L-leucine sulfateshows distinct tubular structure, while polysodiumN-undecenoyl-L-valine sulfate also shows tubular morphology but without any distinct order of the tubes. Onthe other hand, polysodium N-undecenoyl-L-isoleucinesulfate (poly-L-SUCILS) displays random distribution ofcoiled/curved filaments with heavy association of tightlyand loosely bound water. All three polymeric sulfatedsurfactants are compared for enantioseparation of a broadrange of structurally diverse racemic compounds at veryacidic, neutral, and basic pH conditions in micellarelectrokinetic chromatography (MEKC). A small combinatorial library of 10 structurally related phenylethylamines (PEAs) is investigated for chiral separation underacidic and moderately acidic to neutral pH conditionsusing an experimental design. In contrast to neutral pHconditions, at acidic pH, significantly enhanced chiralresolution is obtained for class I and class II PEAs dueto the compact structure of polymeric sulfated surfactants.It is observed that the presence of a hydroxy group onthe benzene ring of PEAs resulted in deterioration ofenantioseparation. A sensitive MEKC-mass spectrometry(MS) method is developed for one of the PEAs (e.g.,(±)-pseudoephedrine) in human urine. Very low limit ofdetection (LOD) is obtained at pH 2.0 (LOD 325 ng/mL),which is ~16 times better compared to pH 8.0 (LOD 5.2
g/mL). Another broad range of chiral analytes (
-blockers, phenoxypropionic acid, benzoin derivatives, PTH-amino acids, benzodiazepinones) studied also providedimproved chiral separation at low pH compared to high-pH conditions. Among the three polymeric sulfated surfactants, poly-L-SUCILS with two chiral centers on thepolymer head group provided overall higher enantioresolution for the investigated acidic, basic, and neutralcompounds. This work clearly demonstrates for the firsttime the superiority of chiral separation and sensitive MSdetection at low pH over conventional high-pH chiralseparation and detection employing anionic chiral polymeric surfactants in MEKC and MEKC-MS.
g/mL). Another broad range of chiral analytes (-blockers, phenoxypropionic acid, benzoin derivatives, PTH-amino acids, benzodiazepinones) studied also providedimproved chiral separation at low pH compared to high-pH conditions. Among the three polymeric sulfated surfactants, poly-L-SUCILS with two chiral centers on thepolymer head group provided overall higher enantioresolution for the investigated acidic, basic, and neutralcompounds. This work clearly demonstrates for the firsttime the superiority of chiral separation and sensitive MSdetection at low pH over conventional high-pH chiralseparation and detection employing anionic chiral polymeric surfactants in MEKC and MEKC-MS.