A study of the thermodynamics of retention of block (co)oligomers using high-performance liquid chromatography/mass spectrometry.
Chromatographic behavior of block (co)oligomers of oxyethylene (EO) and oxypropylene (PO) surfactants in reversed-phase HPLC (RP-HPLC) was investigated. The retention of EO/PO block (co)oligomers depends on the distribution of the individual monomer repeat units, but the sequence of the individual blocks also plays a (less significant) role. The enthalpic and entropic contributions of the EO and PO repeat units to the retention were determined from the data measured at changing temperature. In RP-HPLC, the effect of the repeat PO units on separation is higher than the influence of the repeat EO units. In addition to the enthalpic contributions, the retention is significantly influenced by the entropy (possibly by the change of conformation and solvation of adsorbed molecules); dual molar mass distribution according to the number of EO and PO units complicates correct assignment of the chromatographic peaks to the individual (co)oligomers in complex samples based only on the chromatographic retention data. In spite of imperfect chromatographic separation, HPLC coupled with positive ion mode atmospheric pressure chemical ionization mass spectrometry allow identifying unambiguously the dual monomer distribution in the samples of EO-PO block (co)oligomers.
Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 53210 Pardubice, Czech Republic.
Lenka
L
Ceslová
Pavel
P
Jandera
Petr
P
Cesla
D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004852:Epoxy Compounds / Q000737:chemistry; D005027:Ethylene Oxide / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D011092:Polyethylene Glycols / Q000737:chemistry*; D013816:Thermodynamics
D004852:Epoxy Compounds; D011092:Polyethylene Glycols; D005027:Ethylene Oxide; C009068:propylene oxide