title: Flow rate dependent extra-column variance from injection in capillary liquid chromatography.
abstract: Efficiency and resolution in capillary liquid chromatography (LC) can be significantly affected by extra-column band broadening, especially for isocratic separations. This is particularly a concern in evaluating column bed structure using non-retained test compounds. The band broadening due to an injector supplied with a commercially available capillary LC system was characterized from experimental measurements. The extra-column variance from the injection valve was found to have an extra-column contribution independent of the injection volume, showing an exponential dependence on flow rate. The overall extra-column variance from the injection valve was found to vary from 34 to 23 nL. A new mathematical model was derived that explains this exponential contribution of extra-column variance on chromatographic performance. The chromatographic efficiency was compromised by ∼130% for a non-retained analyte because of injection valve dead volume. The measured chromatographic efficiency was greatly improved when a new nano-flow pumping system with integrated injection valve was used.
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Aggarwal
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Sonika
authors.initials: S
authors.lastname: Sharma
authors.affiliation: Department of Statistics, Brigham Young University, Provo, UT 84602, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Lawson
authors.affiliation: Department of Statistics, Brigham Young University, Provo, UT 84602, USA.
authors.forename: H
authors.initials: H
authors.lastname: Dennis Tolley
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA. Electronic address: milton_lee@byu.edu.
authors.forename: Milton L
authors.initials: ML
authors.lastname: Lee
mesh_terms: D002853:Chromatography, Liquid / Q000295:instrumentation / Q000379:methods*; D008962:Models, Theoretical; D010636:Phenols / Q000302:isolation & purification; D014498:Uracil / Q000302:isolation & purification
chemical_list: D010636:Phenols; D014498:Uracil
keywords: Capillary columns; Column efficiency; Extra-column variance; Injection port; Liquid chromatography