title: Coupling Charge Reduction Mass Spectrometry to Liquid Chromatography for Complex Mixture Analysis.
abstract: Electrospray ionization (ESI) of solution mixtures often generates complex mass spectra, even following liquid chromatography (LC), due to analyte multiple charging. Multiple charge state distributions can lead to isobaric interferences, mass spectral congestion, and ambiguous ion identification. As a consequence, data interpretation increases in complexity. Several charge reduction mass spectrometry (MS) approaches have been previously developed to reduce the average charge state of gaseous ions; however, all of these techniques have been restricted to direct infusion MS. In this study, synthetic polyols and surfactants separated by liquid chromatography and ionized by positive mode ESI have been subjected to polonium-210 α-particle radiation to reduce the average charge state to singly charged cations prior to mass analysis. LC/MS analysis of 5000 molecular weight poly(ethylene glycol) (PEG5000) generated an average charge state of 5.88+; whereupon, liquid chromatography/electrospray ionization/charge reduction/mass spectrometry (LC/CR/MS) analysis of PEG 5000 generated an average charge state of 1.00+. The PEG5000 results demonstrated a decrease in spectral complexity and enabled facile interpretation. Other complex solution mixtures representing specific MS challenges (i.e., competitive ionization and isobaric ion overlap) were explored and analyzed with LC/CR/MS to demonstrate the benefits of coupling LC to CR/MS. For example, polyol information related to initiator, identity/relative amount of monomer, and estimated molecular weight was characterized in random and triblock ethylene oxide/propylene oxide polyols using LC/CR/MS. LC/CR/MS is a new analytical technique for the analysis of complex mixtures.
authors.affiliation: Analytical Sciences, The Dow Chemical Company , 1897 Building, Midland, Michigan 48667, United States.
authors.forename: John R
authors.initials: JR
authors.lastname: Stutzman
authors.affiliation: Analytical Sciences, The Dow Chemical Company , Collegeville, Pennsylvania 19426, United States.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Crowe
authors.affiliation: Analytical Sciences, The Dow Chemical Company , Collegeville, Pennsylvania 19426, United States.
authors.forename: James N
authors.initials: JN
authors.lastname: Alexander
authors.affiliation: Analytical Sciences, The Dow Chemical Company , 1897 Building, Midland, Michigan 48667, United States.
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Bell
authors.affiliation: Analytical Sciences, The Dow Chemical Company , Herbert H. Dowweg 5, ADD2/8, 4542 NM Hoek, Netherlands.
authors.forename: Melissa N
authors.initials: MN
authors.lastname: Dunkle