title: Quantifying injection solvent effects in reversed-phase liquid chromatography.
abstract: Peak distortion due to the injection was measured as a function of injection solvent strength, volume, mass, retention factor, and column selectivity. The concept of a method's sensitivity (s) to injection solvent strength was mathematically defined as a vector of theoretical plate counts compared to an ideal vector that does not change with injection solvent strength. Near ideal sensitivity (s>0.90) was measured on all columns with all analytes in low volume injections of 1.25 μL. Increasing the injection volume reduces the measured sensitivity from ideality to a greater extent than increasing the injection mass, with differing values for each column. Using column parameters measured from the hydrophobic-subtraction model and fitting parameters from the acetonitrile excess adsorption isotherm, differences among the columns studied are explained. Decreased ligand density and increased silanol activity provide a consistent peak shape with changes in injection volume or solvent strength. For method development, a quick test is suggested with the ratio of hydrophobic-subtraction column parameters, H/A, to predict the injection solvent sensitivity of a column. As H/A decreases, the sensitivity to injection solvent worsens. Sensitivity to organic modifiers other than acetonitrile are predicted with cited sorbed layer thickness, such that MeOH>EtOH>IPA≈THF≈MeCN, i.e., a strong MeOH diluent is more ideal (better) than a strong MeCN diluent.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390, USA.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: VanMiddlesworth
authors.forename: John G
authors.initials: JG
authors.lastname: Dorsey
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D000327:Adsorption; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D000431:Ethanol / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D007659:Ketones / Q000737:chemistry; D008012:Lidocaine / Q000737:chemistry; D000432:Methanol / Q000737:chemistry; D008956:Models, Chemical; D012997:Solvents / Q000737:chemistry*; D013696:Temperature
chemical_list: D000097:Acetonitriles; D007659:Ketones; D012997:Solvents; D000431:Ethanol; D008012:Lidocaine; D000432:Methanol; C032159:acetonitrile