Single-pump bi-dimensional LC applied to the characterization of derivatized fatty alcohol ethoxylates

• Published in: Journal of separation science 2010-06, Vol.33 (10), p.1398-1404
• Main Authors: Micó-Tormos, Anna, Simó-Alfonso, Ernesto F, Ramis-Ramos, Guillermo
• Format: Article
• Language: English
• Subjects: 2-D HPLC; Acetonitrile; Alcohols; Carbon; Chromatography, Liquid - instrumentation; Chromatography, Liquid - methods; Diphenic anhydride derivatization; Ethoxylated fatty alcohols; Ethylene oxide; Fatty alcohol ethoxylates; Fatty Alcohols - chemistry; Fatty Alcohols - isolation & purification; Heart-cut LC; Hydrocarbons; Oligomers; Separation; Valves
• ISSN: 1615-9306; 1615-9314
• DOI: 10.1002/jssc.200900723

A column selection valve and a 6-port 2-position injection valve were combined to implement bi-dimensional LC in a system driven by a single pump. The system was applied to the separation of linear fatty alcohol ethoxylates with 12-18 carbon atoms in the hydrocarbon moiety, previous derivatization with diphenic anhydride. Separation on the first separation dimension (C₁) was carried out with a propyl-diol column and an acetonitrile/aqueous ammonium acetate gradient. Fatty alcohol ethoxylate hydrocarbon series (oligomers with the same number of carbon atoms in the alkyl chain but differing in the number of ethylene oxide units) were resolved without distinguishing the oligomers within the series. Selected segments of the eluate of C₁ were transferred to the second column (C₂), where the successive oligomers within the isolated series were resolved by using either an octyl-silica or a pentafluoro-phenyl-propyl column and an acetonitrile/water gradient. Flow stopping at C₁ during system re-conditioning and elution along the second dimension did not produce any noticeable band broadening. Overlapping of the non-ethoxylated and mono-ethoxylated oligomers with other oligomers within the series was avoided by eluting the pentafluoro-phenyl-propyl column at low temperatures (3°C).