V O L U M E 26, NO. 10, O C T O B E R 1 9 5 4 (18) hlcFarren, E. F., ANAL. CHEM.,23, 168 (1951). (19) McFarren, E. F., and Mills, J. A., Ibid., 24, 650 (1952).
(20) Miller, J. hl., and Rockland, L. R., Arch. Biochem. and Biophys., 40,416 (1952). (21) Muller, R. H., and Clegg, D. L., . b . i L . CHEM.,23, 403 (1951). (22) Pratt. J. J., and Auclair. J. L., Science, 108, 213 (1948). (23) Rockland, L. E., Blatt. J. L., and Dunn, &I.S., -bar.. CHEM., 23, 1142 (1951). (24) Rockland, L. B., and Dunn, M. S., Science, 109, 539 (1949). (25) Rockland, L. B., Underwood, J. C . , and Bearens, E. A, C a l i f . Citrograph, 35,490 (1950). (26) Shibatani, A., and Kukuda. 3I.,Bioche?n. J . ( J a p a n ) , 38, 181 (1951). (27) Strain, H. H., A i v . i L . CHEM.,22,41 (1950). (28) Toennies, G.. and Iiolb, J. L., Jbid., 23, 823 (1951).
I563 (29) Underwood. J. C., and Rockland, L. B., Food Research, 18, 17 (1953). (30) Wernimont, G., and Hopkinson, F. J., IND. END. CHEM.,d N A L . ED.,15,272 (1943). (31) White, J. W., and Maher, J., Arch. Biochenz. and Biophys., 42, 360 (1953).
RECKIVED for review June I;, 1953. Accellted June 7 , 1954, Presented before the Division of Analytical Cheinistry a t they123rd Meeting ofjthe AMERICAX CHEMICAL SOCIETY, Los Angeles. Calif.. March 1953. Mention of special instruments or materials throughout this paper does not imply that they are endorsed or recommended by the Department of Agriculture o r e r others of a similar nature not mentioned.
Study of Solvents Used in Adsorption Chromatography PATTERSON B. M O S E L E Y ' and A R T H U R L. L E R O S E N ~ Coates Chemical Laboratories, Louisiana State University, Baton Rouge, La.
J A C K K. C A R L T O N lnstitute of Science and Technology, University o f Arkansas, Fayetteville, Ark,
Several pure solvents, as wTell as binary and ternary solvent mixtures, were investigated as developers in adsorption chromatography. The R values of a number of organic compounds developed with the pure solvents and adsorbed on silicic acid and calcium hydroxide make available useful data regarding the developing power of these solvents. Two- and three-component solvent mixtures were used in developing o-nitroaniline on silicic acid. These studies offer data on solvent mixtures covering a wide range of developing power. Observations of previous workers on the lack of correlation between certain properties of the solvent and its developing power are substantiated.
N
LXEROUS studies have been reported in which an effort was
made to determine the role of solvent in adsorption processes. Patrick and Jones ( 6 ) in a n attempt, t o correlate solubilit'y of the absorptive in the Folvent with adsorption affinity, found that as the absorption on silica gel from nitrobenzene, toluene. carbon tetrachloride, carbon disulfide. and kerosine was higher., the less soluble wap the adsorptive iii the solvent. Another investigator ( ? ) concluded that no valid correlation could be made between adsorptive solubility and atlsorption affinity. Considering the pclarity of the solvent, He>-maiin and Boye ( 2 ) suggested that, if adsorption depends 011 t,he dipole moment of the adsorptive, solvents having high dipole moments should compete more strongly with the adsorptive in adsorption. However, those authors ( 2 ) found no corrclatioii between dipole moment of the solvent and adsorption. After a s h d y of the adeorption of a number of adsorptivities from a variety of solvents on alumina. Jacques and Mathieu ( 4 j observed t,hat in a binary mixture the component having the higher dielectric constant was more strongly adsorbed; in binary mixtures, where one ?omponent was kept the same for all runs, the adsorption of the coniponent of higher dielectric constant increased as the difference in dielectric constant between the two increased; in ternarv mixtures, the component with the highest dielectric constant was most strongly adsorbed. In addition to dipolar attractions among solvent, adsorptive and adsorbent hydrogen bonding must be given consideration. 1
2
Present address. Hercules Powder Co., U'ilnlington. Del Deceased
Elder and Springer ( 1 ) . a~suniingthe structure of silica gel to yield the grouping, 0
--st
// \\
OH picture adsorption of fatty acids to occur i n this nlrtnner 0
\
HO
//
OH... . .O
Schroetler ( 8 ) has shown that certain derivatives of diphenylamiile and A-ethylaniline exhibit K value8 which can be explained on the basis of intramolecular hydrogel1 bond formation, or the lack of it, depending on the position of substitution of a nitro group. For example, 2-nitrotlipheiiylnmine is much less strongly adsorbed than ~-nitrodiphenylaiiiiiie,the difference being attributed essentially to the freeing of the nitro group in the 4position as compared to its limited availability in the 2-position where it is effectively bound through a hydrogen bridge t o the amino nitrogen. LeRosen and coworkers ( 5 ) have studied the effect of position in ortho and para substituted benzenes and have also found t h a t decreased adsorption is observed where intramolecular hydrogen bonds are possible. Hoyer (3) has also investigated the significance of hydrogen bond formation in chromatographic processes. Each of the examples cited involves the study of the adsorption of certain organic molecules from an inert solvent. It should be remembered that, given a solvent such as methanol which is itself capable of hydrogen bonding to the adsorbent, competition offered by the solvent may be strong enough to prevent the ntlsorption of the organic compound being chromatographed. In this case a n R value of 1.00 is measured. I n this ptudy a preliminary survej- was made of a number of pure solvents. This was followed by an extensive study of several two- and t,hree-component solvent mixtures of varying compoFiition employing o-nitroaniline as the substance to be chromatographed. It is hoped t>hatthe data made available by this study will aid ot'her researchers in selecting the appropriate solvent or solvent mixture for the separation in which they are interested.
ANALYTICAL CHEMISTRY
1564
______ Table I.
R j \-dues of \-arious Organic Compounds on Silicic Acid (Using pure solvents as developers) Adsorptive
Solvent Cyclohexane Carbon tetrachloride Carbon disulfide Ethylbenzene C hlorof oriii Ether Chlorobenzene Methanol Acetic acid Ethyl acetate Acetone Sitrohenzene
Trietiiylamine
