Fritless Packed Columns for Capillary Electrochromatography:  Separation of Uncharged Compounds on Hydrophobic Hydrogels

Abstract

A novel column is described that does not require frits to keep packing material within a capillary. A continuous bed is prepared in situ in aqueous solution by radical copolymerization of N-isopropylacrylamide and 2-acrylamido-2-methylpropanesulfonic acid (the resultant gel is denoted poly(AMPS-co-IPAAm). N,N'-Methylenebisacrylamide is used for cross-linking. On the application of an electrical field, electroosmotic flow (EOF) is developed in the bed along the capillary, where fluid propulsion would be otherwise difficult to achieve. The resultant EOF transports neutral compounds through the column without forcing the gel out of the capillary. Examination of the fluid motion in the continuous bed using a video microscope system and an image processor shows a relatively flat flow profile of EOF. The bed functions as the stationary phase for reversed-phase capillary electrochromatography (CEC). This new approach is an alternative to packed capillary columns which have been used previously in CEC. A high efficiency is obtained for a steroid which is separated on a 4.0% total monomer concentration (T), 10.0% degree of cross-linking (C), and 10.0% mole fraction of AMPS in the total monomer (S), poly(AMPS-co-IPAAm) column. A mixture of polyaromatic hydrocarbons is separated on a 6.9% T, 5.8% C, and 5.5% S poly(AMPS-co-IPAAm) column. The capacity factor of benzo[a]pyrene increases from 0.63 to 1.91 as the acetonitrile content in a Tris-boric acid buffer is decreased from 45 to 30% (v/v). The run-to-run RSD of analyte migration time is less than 0.73%, and the day-to-day RSD is acceptable. Potential benefits of this approach are also mentioned.

Enantiomer Separation by Capillary Electrochromatography Using Fritless Packed Columns

“…Slightly crosslinked gels and liquid (non-crosslinked) gels were employed for the enantiomer separations of Dns-AAs, homatropine and atropine. Koide and Ueno 29,30 prepared charged gel columns according to the previously reported method [31][32][33] with some modifications. A mixture of either poly β-CD or caboxymethyl β-CD polymers (chiral selector), Tween 20, AAm, BIS and AMPS (for the preparation of negatively charged gels) or N-(2-acrylamidoethyl)triethylammonium iodide (for the preparation of positively charged gels) in a Tirs-boric acid buffer (pH 8.1) containing ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) was introduced into a fused silica capillary and allowed to stand for >5 h. The resultant gels generated substantial EOF, the direction of which depended on the charged monomer added, and therefore could be used to separate neutral enantiomers.…”

Capillary electrophoresis separation of neutral organic compounds, pharmaceutical drugs, proteins and peptides, enantiomers, and anions

“…Over the last 20 years CE has demonstrated to be a fast and versatile analytical technique that combines simplicity with high reproducibility [2]. Narrow-diameter polyimide-coated fused silica capillaries assures flexibility and allows efficient heat dissipation, thereby permits the use of high field strength resulting in separation efficiencies over [105][106] where Ld is the length of the capillary to the detector, & is the migration time, and V is the applied voltage. where eo is the dielectric constant, y is the viscosity of the buffer, and 5 is the zeta potential on the surface.…”

Enantiomeric Separations by Capillary Electrochromatography with Charged Polyacrylamide Gels Incorporating Chiral Selectors

“…At present, capillaries packed with the typical stationary phase for HPLC are used in various CEC studies. 3,4 On the other hand, monolithic stationary phases, [5][6][7][8][9][10][11][12][13][14][15] which are ungranular polymeric separation media, are attracting increasing attention in the field of CEC due to their simple preparation methods, wide variety of functionalization and good stability.…”