title: Regeneration of tetrabutylammonium ion-pairing reagent distribution in a gradient elution of reversed phase ion-pair chromatography.
abstract: The regeneration of ion-pairing reagent distribution on liquid chromatography columns after gradient elution has been well recognized as the cause for long column equilibration time, a major drawback associated with gradient elution reverse phase ion-pair chromatography. To date, the  majority of studies have focused on optimizing the separation conditions to shorten the equilibration time. There is limited understanding of the ion-pairing reagent distribution process between the mobile phase and stationary phase in the course of gradient elution, and subsequent column  re-equilibration. The focus of this work is to gain a better understanding of this process. An ion-pair chromatographic system, equipped with a YMC ODS C(18) column and a mobile phase containing tetrabutylammonium (TBA) hydroxide as the ion-pairing reagent, was used in the study.  The TBA distribution profile was established by measuring its concentration in the eluent fractions collected during the gradient cycle using different column equilibration times with an ion chromatographic method. Furthermore, the analyte retention time was evaluated as the function of the  column equilibration time and TBA concentration in the mobile phase. The column equilibration and its impact on the method robustness will also be discussed.
authors.affiliation: Analytical R&D, Research and Development, Bristol Myers-Squibb, New Brunswick, NJ, USA. jin.zhang@bms.com
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Thomas
authors.initials: T
authors.lastname: Raglione
authors.forename: Qinggang
authors.initials: Q
authors.lastname: Wang
authors.forename: Brent
authors.initials: B
authors.lastname: Kleintop
authors.forename: Frank
authors.initials: F
authors.lastname: Tomasella
authors.forename: Xiaozhong
authors.initials: X
authors.lastname: Liang
mesh_terms: D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange / Q000295:instrumentation* / Q000379:methods; D056148:Chromatography, Reverse-Phase; D007202:Indicators and Reagents / Q000737:chemistry; D016014:Linear Models; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013997:Time Factors
chemical_list: D007202:Indicators and Reagents; D000644:Quaternary Ammonium Compounds; C009405:tetrabutylammonium