title: How to utilize the true performance of monolithic silica columns.
abstract: Ways of utilizing the true separation efficiency of monolithic silica (MS) columns were studied. The true performance of MS columns, both regular-sized (rod-type clad with PEEK resin, 4.6 mm ID, 10 cm) and capillary sized (in 100 or 200 microm ID fused silica capillary, 25-140 cm) was evaluated by calculating the contribution of extra-column effects. HETP values of 7-9 microm were observed for solutes having retention factors (kvalues) of up to 4 for rod columns and up to 15 for a capillary column. The high permeability of MS columns allowed the use of long columns, with several connected together in the case of rod columns. Narrow-bore connectors gave good results. Peak variance caused by a column connector ranges from 50 to 70% of that caused by one rod-type column for up to three connectors or four columns in 80% methanol, but the addition of a 4th or 5th connector to add a 5th and 6th column, respectively, caused a much greater increase in peak variance, especially for long-retained solutes, which is greater than the variance caused by one rod column. Rod columns seem to show slightly lower efficiency at a pressure higher than 10 MPa or so. The use of acetonitrile-water as a mobile phase better preserved the ability of individual rod columns to generate up to 100,000 theoretical plates with 14 columns connected. Methods for eliminating extra-column effects in micro-HPLC were also studied. Split injection and on-column detection resulted in optimum performance. A long MS capillary measuring 140 cm produced 160,000 theoretical plates. The column efficiency of a capillary column was not affected by the pressure, showing advantages over the rod columns that exhibited peak broadening caused by connectors and pressure.
authors.affiliation: Department of Polymer Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan. ikegami@kit.ac.jp
authors.forename: Tohru
authors.initials: T
authors.lastname: Ikegami
authors.forename: Edith
authors.initials: E
authors.lastname: Dicks
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Hironobu
authors.initials: H
authors.lastname: Morisaka
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tokuda
authors.forename: Karin
authors.initials: K
authors.lastname: Cabrera
authors.forename: Ken
authors.initials: K
authors.lastname: Hosoya
authors.forename: Nobuo
authors.initials: N
authors.lastname: Tanaka
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation* / Q000379:methods*; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D012822:Silicon Dioxide