1552
ANALYTICAL CHEMISTRY, VOL. 62, NO. 14, JULY 15, 1990
tential changes from -29 mV without an external field to -35 mV with a -5 kV potential gradient. The absolute value of the { potential decreases from -29 mV without an external field to about 0 mV with a +5 kV potential gradient. The polarity of the {potential can be reversed at +6 kV potential gradient. These preliminary experimental results indicate that the electroosmosis can be enhanced, decreased, eliminated, and even reversed by simply using an external electric field to control the f potential at the aqueous/inner capillary interface. The proposed concept involving the use of an additional electric potential from outside the capillary for controlling the electroosmosis will be verified again by using the neutral marker method (13,14). The studies for enhancing separation resolution of biomolecules in CZE and in micellar electrokinetic capillary chromatography with the control of electroosmosis will be followed. ACKNOWLEDGMENT We thank Andrew G. Ewing for his helpful discussions.
LITERATURE CITED Virtanen, R. Acta Polytech. Scand. 1974, 723, 1. Wailingford, R. A.; Ewing, A. G. A&. Chromtogr. 1989, 2 9 , 1. Rice. C. L; Whitehead R. J. phvs. Chem. 1985, 7 1 , 4017. Jorgenson, J. W.: Lukacs, K. D. Science 1983, 222, 266. (5) Hjerten, S. Chromatogr. Rev. 1987, 9 , 122. (6) Herren, B. J.; Shafer, S. G.; Aistlne, J. V.; Harris, J. M.; Snyder, R. S. J . Colloid Interface Sci. 1987, 175, 46. (7) Hjerten, S. J . Chromatog. 1985, 347, 191. (8) Lauer, H. H.; McManigiii, D. Anal. Chem. 1988, 5 8 , 166. (9) McCormick, R. M. Anal. Chem. 1988, 6 0 , 2322. (10) Huang, X.: Gordon, M. J.; Zare, R. N. Anal. Chem. 1988, 60, 1837. (11) Pretorius, V.; Hopkins, 8.J.; Schieke, J. D. J. Chromatogr. 1974, 264, 385. (12) Tsuda, A.; Nomura, K.; Nakagawa, G. J. Chromatogr. 1983, 2 6 4 , 385. (13) Tsuda, A.; Nakagawa, G.; Sato, M.; Yagi, K, J. Appl. Biochem. 1983. 5 , 330. (14) Waibroehl, Y.; Jorgenson, J. W. Anal. Chem. 1988, 58, 479. (1) (2) (3) (4)
RECEIVED for review February 9, 1990. Accepted April 18, 1990. Support for this work by Minta Martin Foundation and Engineering Research Center of the University of Maryland is gratefully acknowledged.
CORRECTION Nile Red as a Solvatochromic Dye for Measuring Solvent Strength in Normal Liquids and Mixtures of Normal Liquids with Supercritical and Near Critical Fluids Jerry F. Deye, T. A. Berger, and Albert G. Anderson (Anal. Chern. 1990, 62, 615-622). Table I contains two errors. Solvent 53 should be N,Ndimethylaniline and solvent 74 should be C02/methanol (9O:lO) (v/v). On p 618, the next to the last sentence in the first column should read: It also produces a bathochromic wavelength shift consistent with stabilization of the excited state in n-a* or T-H* electronic transitions and comparable with the a* scale of Kamlet and Taft (16).
