title: Transient Ion-Pair Separations for Electrospray Mass Spectrometry.
abstract: We report a novel ion-pair chromatography (IPC) approach for liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS), where the eluent does not contain any ion-pairing reagent (IPR). The IPR is injected on the column, much like the sample, and moves down the column. Significant amounts of a high retention factor IPR is injected, resulting in a transient but reproducible regional coating that progresses along the column. The sample is injected after a brief interval. The sample components interact with the IPR coated region during their passage; the chosen eluent gradient elutes the analytes of interest into the mass spectrometer before the IPR. Following analyte elution, the gradient is steeply raised, the IPR is washed out, and the effluent is sent to waste via a diverter valve until it is fully removed. As the nature of the analyte retention continuously changes along the column and with time, we call this transient ion-pair separation (TIPS). As the IPR never enters the MS, TIPS addresses two major drawbacks of IPC for ESI-MS: it avoids both ion suppression and ion source contamination. The potential of the generic approach for other modes of separation is discussed. An illustrative separation of two small inorganic ions, iodate and nitrate, is demonstrated on a reverse phase column by a transient prior injection of hexadecyltrimethylammonium chloride as IPR.
authors.affiliation: Senomyx, Inc., 4767 Nexus Centre Drive, San Diego, California 92121, United States.|Department of Chemistry and Biochemistry, The University of Texas at Arlington , Arlington, Texas 76019-0065, United States.
authors.forename: Hanghui
authors.initials: H
authors.lastname: Liu
authors.affiliation: Senomyx, Inc., 4767 Nexus Centre Drive, San Diego, California 92121, United States.|Department of Chemistry and Biochemistry, The University of Texas at Arlington , Arlington, Texas 76019-0065, United States.
authors.forename: Lily
authors.initials: L
authors.lastname: Lam
authors.affiliation: Senomyx, Inc., 4767 Nexus Centre Drive, San Diego, California 92121, United States.|Department of Chemistry and Biochemistry, The University of Texas at Arlington , Arlington, Texas 76019-0065, United States.
authors.forename: Bert
authors.initials: B
authors.lastname: Chi
authors.affiliation: Senomyx, Inc., 4767 Nexus Centre Drive, San Diego, California 92121, United States.|Department of Chemistry and Biochemistry, The University of Texas at Arlington , Arlington, Texas 76019-0065, United States.
authors.forename: Akinde F
authors.initials: AF
authors.lastname: Kadjo
authors.affiliation: Senomyx, Inc., 4767 Nexus Centre Drive, San Diego, California 92121, United States.|Department of Chemistry and Biochemistry, The University of Texas at Arlington , Arlington, Texas 76019-0065, United States.
authors.forename: Purnendu K
authors.initials: PK
authors.lastname: Dasgupta