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The combined effect of acetonitrile and urea on the separation of polycyclic aromatic hydrocarbons using sodium dioctyl sulfosuccinate in electrokinetic chromatography
Author(s) -
Luong John H. T.
Publication year - 1998
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.1150190841
Subject(s) - chemistry , fluoranthene , acetonitrile , chromatography , micellar electrokinetic chromatography , pyrene , urea , elution , solvophobic , sodium , alkylbenzenes , electrokinetic phenomena , capillary electrophoresis , sodium dodecyl sulfate , molecule , organic chemistry , benzene
Sodium dioctyl sulfosuccinate (DOSS) or sodium di2‐ethylhexyl sulfosuccinate, a relatively nontoxic and negatively charged surfactant, was selected and optimized for the capillary electrophoretic separation of the 16 Environmental Protection Agency (EPA) priority polycyclic aromatic hydrocarbons (PAHs). This pseudostationary phase displayed selectivities for PAHs which were somewhat similar to the C 18 phase in reversed‐phase high performance liquid chromatography (HPLC). At high DOSS concentrations (> 30 m M ), the hydrophobic interaction between DOSS and PAHs was pronounced and led to stronger retention of the latter. Consequently, acetonitrile was added to the running buffer to facilitate the elution of hydrophobic PAHs. In the absence of micelles, the separation mechanism was attributed to the solvophobic association of the PAH molecules with hydrophobic chains of the DOSS surfactant and there was a linear correlation between log k (retention factor) and the double bond number of the PAH. However, separations performed in an optimized buffer containing both DOSS and acetonitrile were not able to provide satisfactory performance. The separation of the 16 PAHs was then appreciably improved by adding urea to the running buffer to widen the separation window. At a high sample loading with UV detection, except for benzo[ a ]pyrene, benzo[ b ]fluoranthene and benzo[ k ]fluoranthene, all other PAHs were practically baseline‐resolved using an optimized running buffer containing 50 m M DOSS, 35% acetonitrile and 5 M urea in 8–10 m M borate, pH 9. Laser‐induced fluorescence permitted a very low sample loading and under such a running condition, a baseline resolution was obtained for these three most difficult PAHs. The addition of urea at this level, however, exhibited a noticeable quenching effect on the PAH fluorescent signal.