The use of polyethyleneimine-coated capillaries for the capillary electrophoretic separation of substituted phenols has been demonstrated. Efficient separation of phenols has been achieved in the coated capillaries. α§ 1997 Academic Press Substituted phenols are of great environmental importance mostly because of their high toxicity. In recent years, capillary electrophoresis (CE) has become a suitable alternative to high-performance liquid chromatography (HPLC) for the analysis of phenolic compounds. The analysis of a series of phenols using capillary zone electrophoresis and micellar electrokinetic chromatography (MEKC) has been reported (1-6).
The aim of this investigation is to introduce the use of polyethyleneimine (PEI)coated capillaries for the analysis of substituted phenols. To the best of our knowledge, all capillary electrophoretic separations of phenols described in the literature have been performed using uncoated fused silica capillaries. PEI was first introduced by Towns and Regnier (7) as a coating agent in CE and developed by others (8-10). This coating is different from most polymer layers because PEI is a cationic polymer; therefore, the surface bears a positive charge and this causes the reversal of electroosmotic flow. The application of PEI-coated capillaries has been reported, until now, only for the separation of basic proteins at acidic pH or compounds having the same positive charge as the surface. In the present study, a recently developed coating procedure was performed (11), and the applicability of PEI-coated capillaries for the seperation of phenols was shown.
EXPERIMENTAL
Instrumentation
Separations were carried out with a commercial CE injection system (Prince Technologies B. V. (The Netherlands) in combination with an on-column variable-wavelength UV-visible detector (Lambda 1000, Bishoff, Germany). The wavelength was set at 210 nm. The fused silica capillaries used for separation experiments were 75 mm in i.d. They were obtained from Polymicro Technologies (Pheonix, AZ). The coating procedure was described before (11). The total and effective lengths of capillaries are indicated in the figures.