title: Study of complexation in methanol/water mixtures by infrared and Raman spectroscopy and multivariate curve resolution-alternating least-squares analysis.
abstract: The structure of the mobile phase in liquid chromatography plays an important role in the determination of retention behavior on reversed-phase stationary materials. One of the most commonly employed mobile phases is a mixture of methanol and water. In this work, infrared and Raman spectroscopic methods were used to investigate the structure of species formed in methanol/water mixtures. Chemometric methods using multivariate curve resolution by alternating least-squares analysis were used to resolve the overlapped spectra and to determine concentration profiles as a function of composition. The results showed that the structure of these mixtures could be described by a mixture model consisting of four species, namely, methanol, water, and two complexes, methanol/water (1:1) and methanol/water (1:4). The spectral frequencies and concentration profiles found from the Raman and infrared measurements were consistent with one another and with theoretical calculations.
authors.affiliation: Department of Chemistry, Virginia Commonwealth University, PO Box 842006 Richmond, Virginia 23284-2006, USA.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Holden
authors.forename: Sally S
authors.initials: SS
authors.lastname: Hunnicutt
authors.forename: Raymundo
authors.initials: R
authors.lastname: Sánchez-Ponce
authors.forename: John M
authors.initials: JM
authors.lastname: Craig
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Rutan
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D020650:Combinatorial Chemistry Techniques; D006860:Hydrogen Bonding; D016018:Least-Squares Analysis; D046911:Macromolecular Substances; D000432:Methanol / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015233:Models, Statistical; D008968:Molecular Conformation; D015394:Molecular Structure; D015999:Multivariate Analysis; D044367:Phase Transition; D012996:Solutions; D012997:Solvents / Q000737:chemistry; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014867:Water / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D012996:Solutions; D012997:Solvents; D014867:Water; D000432:Methanol