title: Application of partially fluorinated carboxylic acids as ion-pairing reagents in LC/ESI-MS.
abstract: This report describes the application of partially fluorinated carboxylic acids as ion-pairing reagents for basic analytes in high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (LC/ESI-MS) in positive-ion mode. Partially fluoridated carboxylic acids such as difluoroacetic acid, 3,3,3-trifluoropropionic acid and 3,3,3-trifluoromethyl-2-trifluoromethylpropionic acid functioned as volatile paired-ion similarly as trifluoroacetic acid (TFA). These acids provided basic analytes larger retention factor (k) compared to acetic acid or formic acid in LC. The ESI-MS signal strength of analytes with these acids were higher than that of TFA and was analogous to that of acetic acid or formic acid. The performances of partially fluorinated carboxylic acids in LC and ESI-MS for basic analytes were analyzed by multivariate statistical analysis using physicochemical descriptors of acids. Equations obtained in the analysis enabled us the quantitative evaluation of the performance of fluorinated carboxylic acids as ion-pair reagents for basic analytes in LC/ESI-MS.
authors.affiliation: DDS Research, Global Formulation Research, Pharmaceutical Science and Technology Core Function Unit, Eisai Product Creation Systems, Eisai Co. Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan. Electronic address: e-yamamoto@hhc.eisai.co.jp.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Yamamoto
authors.affiliation: Department of Molecular & Cellular BioAnalysis Graduate School of Pharmaceutical Sciences Kyoto University, 46-29 Yoshida-shimoadachichou, Sakyo-ku, Kyoto 616-8501, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ishihama
authors.affiliation: Pharmaceutical Science and Technology Core Function Unit, Eisai Product Creation Systems, Eisai Co. Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Asakawa
keywords: Drugs; Fluorinated carboxylic acid; Ion pair; LC; MS; Peptides