title: Implementation of a design of experiments to study the influence of the background electrolyte on separation and detection in non-aqueous capillary electrophoresis-mass spectrometry.
abstract: Non-aqueous capillary electrophoresis (NACE) background electrolytes are most often composed of a mixture of methanol and acetonitrile (ACN) with soluble ammonium salts added as electrolyte. In this study on NACE-MS, we used a mixture of glacial acetic acid and ACN giving rise to an acidic background electrolyte (BGE) with a very low dielectric constant. Impressive changes in selectivity and resolution were observed for structurally closely related indole alkaloids including diastereomers upon addition of ammonium formate as electrolyte and upon variation of the solvent ratio. In order to obtain best separation and MS detection conditions and to reveal the influence of the parameters of the BGE on separation and detection and vice versa of the MS parameters on separation, an optimization strategy was employed using a design of experiments in a central composite design with response surface methodology. It was proven that at high electroosmotic flow conditions capillary electrophoretic separations and thus optimization can be realized without interference from the coupling to an MS system. Several significantly interacting parameters were revealed, which are not accessible with classical univariate optimization approaches. With this optimization, alkaloid mixtures from a plant extract of Mitragyna speciosa, containing a large number of diastereomeric compounds were successfully separated.
authors.affiliation: Forschungszentrum Jülich GmbH, Central Division of Analytical Chemistry, Jülich, Germany.
authors.forename: Tjorben Nils
authors.initials: TN
authors.lastname: Posch
authors.forename: Alexander
authors.initials: A
authors.lastname: Müller
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schulz
authors.forename: Michael
authors.initials: M
authors.lastname: Pütz
authors.forename: Carolin
authors.initials: C
authors.lastname: Huhn
mesh_terms: D019342:Acetic Acid / Q000737:chemistry; D000097:Acetonitriles / Q000737:chemistry; D000704:Analysis of Variance; D004573:Electrolytes / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods*; D026121:Indole Alkaloids / Q000032:analysis / Q000302:isolation & purification; D013058:Mass Spectrometry / Q000379:methods*; D032065:Mitragyna / Q000737:chemistry; D008956:Models, Chemical; D010936:Plant Extracts / Q000737:chemistry; D012107:Research Design
chemical_list: D000097:Acetonitriles; D004573:Electrolytes; D026121:Indole Alkaloids; D010936:Plant Extracts; D019342:Acetic Acid; C032159:acetonitrile