Published:Journal of Chromatographic Science,
ISSN 0021-9665Volume
40, Number 2, February 2002, pp. 61-68
A Study of Polyethoxylated Alkylphenols by Packed Column Supercritical
Fluid Chromatography
Brian J. Hoffman and Larry
T. Taylor
Virginia Tech, Department of Chemistry, Blacksburg, VA 24061-0212
Alkylphenol polyethoxylates (APEs) are a widely used group of
nonionic surfactants in commercial production. Characterization of the composition
of APE mixtures can be exploited for the determination of their most effective
uses. In this study sample mixtures contain nonylphenol polyethoxylates and
octylphenol polyethoxylates. The separation of individual alkylphenols by ethoxylate
units is performed by supercritical fluid chromatography (SFC)-UV as well as
normal-phase high-performance liquid chromatographic (HPLC)-UV employing packed
columns. The stationary phase and column length are varied in the SFC setup
to produce the most favorable separation conditions. Additionally, combinations
of packed columns of different stationary phases are tested. The combination
of a diol and a cyano column is found to produce optimal results. An advantage
of using packed columns instead of capillary columns is the ability to inject
large amounts of sample and thus collect eluted fractions. In this regard, fractions
from SFC runs are collected and analyzed by flow injection analysis–electrospray
ionization–mass spectroscopy in order to positively identify the composition
of the fractions. In comparing the separation of APE mixtures by SFC and HPLC,
it is found that SFC provides shorter retention times with similar resolution.
In addition, less solvent waste is produced using SFC.
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