system, the column length can be de creased, thus decreasing t h e needed pressure drop. Particles smaller t h a n 20 μηι are more difficult to pack uni formly, a n d special techniques such as balanced density slurry (20) are needed. However, with care, particles down to 20 μπι can be dry packed to give efficient columns (8). Recent work also shows t h a t t h e shape of small particles need not be spherical for efficient packing. S m a l l porous particles have one distinct advantage over pellicular packings. T h e latter packing usually gives short retention times a n d lowcapacity ratiio value. I t is, therefore, easy to overload t h e pellicular pack ings. I n addition, their price is rather high. Porous supports, on t h e other hand, are usually m u c h less expensive and, owing to their large surface area, can handle larger charges of solute in jections.
References (1) B.L. Karger, L.'R. Snyder, and C. Horvath, "An Introduction to Separa tion Science," Wilev, New York, N.Y., 1973. (2) L. R. Snyder in "Modern Practice of Liquid Chromatography," J". J. Kirkland, Ed., Wiley-Interscience. NewYork, N.Y., 1971.
(3) N. Hadden et al., "Basic Liquid Chro matography," Varian Aerograph, 1971. (4) J. C. Giddings, "Dynamics of Chroma tography," Marcel Dekker, New York, N.Y., 1965. (5) E.Kucera, J. Chromatogr., 19,237 (1965). (6) O. Grubner, in "Advances in Chroma tography," J. C. Giddings and R. A. Keller, Eds., Vol 6, ρ 173, Marcel Dek ker, New York, N.Y., 1966. (7) E. Grushka, J. Phys. Chem., 76, 2586 (1972). (8) J. N. Done, G. J. Kennedy, and J. H. Knox, "Gas Chromatography—1972," S. G. Perry and E. R. Adlard, Eds., ρ 145, Applied Sciences, Essex, England, 1973. (9) J. J. Kirkland, J. Chromatogr. Sci., 10,593(1972). (10) J. J.-Kirkland. J. Chromatogr., 83, 149(1973). (11) R. E. Majors, J. Chromatogr. Sci., 11,9(1973). (12) R . E . Majors and F.R.MacDonald, J. Chromatogr., 83, 169 (1973). (13) J. J. DeStefano and H. C. Beachell, J. Chromatogr. Sci., 10, 654 (1972). (14) J. J. Kirkland in "Gas Chromatogra phy—1972," S. G. Perry and E. R. Ad lard, Eds., ρ 39, Applied Science, Essex, England, Ϊ973. (15) L.R. Snyder, Anal. Chem., 39,398 (1967). (16) L . R . Snyder, J. Chromatogr. Sci., 10,100(1972). (17) L. R. Snyder, ibid., ρ 369. (18) J. A. Schmit, R. A. Henry, R. C. Wil liams, and J. F. Diechman, ibid., 9, 645 (1971). (19) J. H. Knox and G. Vasvari, J. Chro matogr., 63, 181 (1973). (20) R . E . Majors, Anal. Chem., 44, 1722 (1972).
Eli Grushka is assistant professor of chemistry a t t h e S t a t e University of New York a t Buffalo. His B S was ob t a i n e d in 1963 from Long Island Uni versity, a n d his P h D from Cornell University in 1968. H e did postdoctoral work with Professor Giddings a t t h e University of U t a h (1967-1969). D r . Grushka's research interests are in the area of chromatographic theories, e n h a n c e m e n t of chromatographic res olution, t h e utilization of bonded phases and of liquid crystals in chro matography, a n d in measuring physicochemical constants by chromato graphy. He has n u m e r o u s scientific papers in t h e field of separation. Dr. Grushka is a m e m b e r of A C S , AAAS, and t h e Chromatographic Discussion Group. His current address is Hoff m a n n - L a Roche Inc., Nutley, N . J .
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518 A · ANALYTICAL CHEMISTRY, VOL. 46, NO. 6, MAY 1974
