As. Rathore et C. Horvath, CAPILLARY ELECTROCHROMATOGRAPHY - THEORIES ON ELECTROOSMOTIC FLOW IN POROUS-MEDIA, Journal of chromatography, 781(1-2), 1997, pp. 185-195
Citations number
34
Categorie Soggetti
Chemistry Analytical","Biochemical Research Methods
In view of the present interest in capillary electrochromatography (CE
C), theories dealing with electroosmotic flow (EOF) in porous media ar
e reviewed with particular regard to the use of packed capillaries in
CEC. Two of the models found in the pertinent literature are applicabl
e to CEC and give simple analytical solutions, The first of the two mo
dels is based on von Smoluchowski's work as adapted and extended by Ov
erbeek. It deals with EOF through packed capillaries under conditions
of low electric field strength where the EOF varies linearly with the
field strength because there is no polarization of the double layer. O
verbeek's model originally developed for porous media of infinite dime
nsions was modified in an attempt to account for the wall effect that
assumes importance in the packed capillary columns used in CEC. The se
cond model proposed by Dukhin and his coworkers predicts EOF of at lea
st an order of magnitude higher than that expected by classical theori
es. This ''electroosmosis of the second kind'' is believed to occur in
columns packed with conductive particles like ion exchangers at high
electric field strengths when the double layer is polarized and the EO
F becomes a non-linear function of the applied voltage, Conditions nec
essary for electroosmosis of the second kind are likely to arise upon
the further development of CEC when further enhancement of the speed o
f analysis is brought about at electric field strength higher than tha
t employed at present. (C) 1997 Elsevier Science B.V.