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Negatively charged sol‐gel column with stable electroosmotic flow for online preconcentration of zwitterionic biomolecules in capillary electromigration separations
Author(s) -
Li Wen,
Fries David,
Malik Abdul
Publication year - 2005
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.200500172
Subject(s) - chemistry , capillary electrophoresis , electrolyte , chromatography , coating , aqueous solution , electrochromatography , sulfonic acid , sol gel , capillary electrochromatography , analytical chemistry (journal) , chemical engineering , polymer chemistry , organic chemistry , electrode , engineering
A negatively charged sol‐gel coating was developed for on‐line preconcentration of zwitterionic biomolecules in capillary electrophoresis (CE), using asparagine and myoglobin as representative zwitterionic bioanalytes. The sol‐gel coating was created by using a solution containing three precursors: mercaptopropyltrimethoxysilane (MPTMS), tetramethoxysilane (TMOS), and n ‐octadecyltriethoxysilane (C 18 ‐TEOS). The resulting sol‐gel coating contained chemically bonded mercaptopropyl functional groups that were further oxidized by hydrogen peroxide to the corresponding sulfonic acid moieties. Such a surface‐bonded sol‐gel coating can carry a negative charge over a wide range of pH due to the presence of deprotonated sulfonic acid groups. Under favorable pH conditions, the negatively charged sol‐gel coating can facilitate the extraction of positively charged analytes from a zwitterionic sample through electrostatic interaction. This principle was employed to extract myoglobin and asparagine by passing aqueous samples of these zwitterionic analytes through a negatively charged sol‐gel column. The extracted analytes were then desorbed and focused via local pH change and stacking. The local pH change was accomplished by passing a buffer solution with a pH above the solute p I value, while a dynamic pH junction between the sample solution and the background electrolyte was utilized to facilitate solute focusing. The sorption/desorption phenomena could, perhaps, also be explained on the basis of ion‐exchange and local pH junction effects. On‐line preconcentration and analysis results obtained on sulfonated sol‐gel columns were compared with those obtained on an uncoated fused silica capillary of identical dimensions using conventional sample injections. Using UV detection, the presented sample preconcentration technique provided a sensitivity enhancement factor (SEF) on the order of 3×10 3 for myoglobin, and 7×10 3 for asparagine.