Chromatography of Phenols, Especially Alkyl Phenols, on Paper Impregnated with Polyamides W. N. MARTIN and R. M. HUSBAND Research and Development Department, Consolidated Paper Corp., lid., Grand’Mere, Quebec, Canada
b The deficiencies of several procedures for the chromatography of phenolic compounds on paper have been largely overcome or improved with papers impregnated with polyamides. These papers allow a chromatographic separation of a variety of phenols in 2 to 3 hours with water containing 10% of acetic acid or cyclohexane containing 7% of acetic acid. They retain the more volatile phenols sufficiently to allow the detection of very small quantities. The R, values of a limited variety of phenols suggest that such papers may allow considerable interpretation of mixtures of a wider variety of phenolic compounds.
A
of mixtures of simple phenols by chromatography on paper is difficult, especially when they contain relatively volatile alkyl phenols and phenol ethers. Hossfeld (3, 6) did not encounter the problem provided by these latter compounds when he transformed the phenols into the sodium salts of their phenylazobenxenrsulfonic acids, which could be separated conveniently on paper impregnated with sodium carbonate. However, those phenols that contain an aldehyde function para t o the phenolic group suffered displacement of that function during the coupling reaction and therefore could not be identified. And the derivatives of polyhydroxyphenols that are sensitive to air oxidation in alkaline media could not be chromatographed without change, which also disrupted the development of the derivatives of other phenols. Likewise, Bielenberg and Fischer (1) and Rayburn, Harlan, and Hanmer (8) coupled phenols with diazotized pnitroaniline, and Schlogl and Siege1 (10) separated the aryl oxyacetic acid derivatives. HudeEek (6) overcame the volatility of the alkyl phenols, a t least partially, by confining his papers between glass plates. Schleede (9) accomplished good separations of alkyl phenols on paper impregnated with 4% sodium hydroxide solution, but his method is inadequate for polyhydroxyphenols. We record the advantages of separating phenols, particularly the volatile
840
N EFFECTIVE separation
ANALYTICAL CHEMISTRY
alkyl phenols, on paper impregnated with polyamides. To our knowledge, this technique has not been reported, although Carelli, Liguori, and Mele (2) and Grassmann, Hormann, and Hart1 (4) have used columns of powdered polyamides to separate phenols. Although Mac&k and Kubeg (‘7) have reported some comparable separations on paper impregnated with formamide, the insolubility of the polyamides allows considerable advantage to our procedure.
an aqueous solution containing equal volumes of 1% ferric chloride solution and 1% potassium ferricyanide solution which revealed the phenols as permanent blue spots of ferric ferrocyanide. To obtain a permanent chromatogram, the sprayed sheets were immersed in a water bath to dissolve most of the unconsumed spray solution. Most of the phenols were “purified” or of analytical quality. The p-ethylphenol and carvacrol were of technical (Matheson, Coleman and Bell) quality. RESULTS AND DISCUSSION
EXPERIMENTAL
Strips of Whatman paper No. 4, 10 x 57 cm., were impregnated uniformly with a solution of poly(hexamethy1ene adipamide) (Du Pont Nylon 66 staple fiber) in formic acid in the devcloping tray of a commercial photoduplicator. They were fed between the metal guiding fingers, through the solution in the trough to the nip between two electrically driven, rubber-covered rolls where the excess of solution was removed. The papers were then hung in a fume hood to dry. Unfortunately, the width of this machine prohibited the impregnation of wider sheets of paper which would have been convenient for two-dimensional chromatograms. The impregnation could be accomplished by immersing the sheets of papcr or drawing them through the solution in any convenient tank. However, to impregnate papers uniformly a pair of rubber-covered rolls rotating a t uniform speed t o wring out the excess solution is convenient if not essential. To dctcrminc the influence of the proportion of polyamide impregnated into the paper, a series of papers was impregnated with solutions containing 1, 3, 5, and 10% by weight of polyamide in 90% formic acid. The pressing provided by the rolls of the photoduplicator machine was such that the papers retained, after drying, 4 , 7 , 10, and 15%, respectively, of polyamide. The proportion of polyamidc was measured as the gain in weight of the strips of paper conditioned to constant weight for 24 hours a t 24” C. and 50% relative humidity. The various phenols were applied to the paper as solutions in diethyl ether and from a micropipet. The papers were not equilibrated with the developing solvent system before the chromatograms were developcd by the descending technique in a glass tank a t 24” C. They were dried in a forced-draught oven, then developed by spraying with
The polyamides impregnated into paper, like the formamide that Mac& and Kubeg used, bind the phenols through hydrogen bonds (2, 4). However, the polyamides offer the advantage that water and other polar solvents can be used without dissolving or otherwise , disturbing the substrate. They also give “wet strength” to the papers, which can, as a result, be handled readily between repeated developments with different solvents or even washed with water or other solvents when that is convenient or necessary. Thus we have illustrated the use of a washing with water to remove the unconsumed spray reagents to obtain more lasting chromatograms. The impregnated papers developed rapidly with the preferred solvents, requiring only 2 to 3 hours to descend through about 35 cm. Equilibrating them to the atmosphere of the tank did not affect the R, values significantly. Consequently, the chromatograms can be made fairly rapidly. When 7% or less, by wcight, of polyamide was applied to the paper, the proportion in the pathway of the descending spots of phenolic compounds was so small that they spread out into large diffuse spots and the losses of the more volatile ones, such as guaiacol and the cresols, were large. Indeed, with papers containing less than 5% of polyamide, the more volatile phenols could scarcely be detected unless relatively largo quantities were applied. But, withpapers containing 10 to 15% of polyamide, the loss of phenols by volatilization was negligible and the Table I developed spots were disc*. records the smallest & pproximate) quantities of a variety oi phenols that
could be detected as clearly defined spots on such papers. Of a variety of solvent systems t h a t were examined, water containing 10% of acetic acid and cyclohexane containing 7% of acetic acid were most satisfactory for general use. Water alone gave a very satisfactory separation of both the mono- and polyhydroxyphen01s. However, t h e 10% acetic acid solution provided more discrete spots, slightly improved the separation of the inonophenols, and only slightly diminished the separation of the di- and trihydroxyphenols. No such improvement was provided by the addition of acetone, ethanol, propanol, or 2-pro-
Table 1. Approximate Least Amounts of Various Phenols Detectable as Clearly Defined Spots on Papers Impregnated with 10 to 15% of Nylon 66
Compound Phenol o-Cresol m-Cresol p-Cresol o-Ethylphenol p-Ethylphenol 4-n-Propylphenol Carvacrol Guaiacol Eugenol Isoeugenol 1-Naphthol 2-Naphthol Catechol Resorcinol Hydroquinone Phloroglucinol Ferulic acid
Developing Solvent 10% 7% (v./v.) (v./v.) , . acetic 'acetic acid in acid in water, cyclohexane, y Y 170 180 140 220 70 48 24 60 15 65 21 54 24 36 42 78 19 34 24 21 9 18 12 6 6 6 6 6 6 6 6 6 6 6 12 12
panol, which would suggest that the acetic acid played its role by affecting the hydrogen bonding between the polyamides and the phenols. Cyclohexane alone provided extremely long spots and did not move the diand trihydroxyphenols from the starting point. More discrete spots were obtained by adding alcohols or acetone but not chloroform t o the cyclohexane or by saturating it with water. The smallest and most discrete spots were obtained with the addition of 7y0 of acetic acid. Table LI provides the Rj values for a variety of phenolic compounds with these two solvent systems and indicates the influence of the proportion of polyamide in the papers. Each value is the mean from five separate chromatograms, among which the extreme values differed from the mean by no more than 5%. Plots of the many R, values against the proportion of polyamide in different papers showed a rectilinear relationship from 7 t o about 15% polyamide. For the same compounds, the R, values with cyclohexane-acetic acid solution are comparable t o those recorded by MacBk and Kubeg (7) for separations with cyclohexane upon paper impregnated with formamide. The data of Table I1 indicate that it should be possible to achieve considerable insight into a mixture of phenols with these two solvent systems. Indeed, subject to the limitations indicated by those values we have realized very good separations of a considerable variety of mixtures of phenols. Several examples are provided in Table 111. The number of carbon atoms in the side chain of a single unknown alkyl phenol or the several homologs in a mixture of straight-chain alkyl phenols can be determined from the Rj values of a chromatogram developed with water
R, Values at 24' C. of Various Phenols on Papers Impregnated with Nylon 66 Solvent. Cyclohexane-Acetic Solvent. Water-Acetic Acid Acid (7% v./v.) (10% V h . 1 Compound 10% nylon 15% nylon 10% nylon 15% nylon Phenol 0.59 0.47 0.08 0.05 o-Cresol 0.47 0.36 0.22 0.14 m-Creso1 0.13 0.08 0.47 0.36 p-Cresol 0.14 0.09 0.47 0.36 o-Ethylphenol 0.34 0.23 0.33 0.20 p-Et hylphenol 0.36 0.23 0.24 0.13 4-n-Propylphenol 0.21 0.11 0.31 0.21 n. i n Carvacrol 0.58 0.42 Guaiacol 0.13 0.09 Eugenol 0.77 0.68 0.65 0.55 0.10 0.06 0.06 0.04 Catechol 0 0 Resorcinol 0 0 0.48 0 38 Hydroquinone 0.57 0.45 0 0 Phloroglucinol 0 0 0.39 0.31 Ferulic acid 0.02 0.01 0.28 0.13 Table
II.
or water-acetic acid. Each additional methylene group then reduces the RI value by 0.11 to 0.15 unit. Thus (with 10% nylon): phenol = 0.59; cresols = 0.47; ethylphenols = 0.33 to 0.36; 4-n-propylphenol = 0.21. The data suggest that if, instead, the additional methylene group is at another nuclear position, a lesser change results (4-npropylphenol = 0.21; carvacrol = 0.17). However, we lacked the appropriate phenols t o extend this correlation. I n a two-dimensional chromatogram, a primary development with cyclohexane-acetic acid would separate phenol, the alkyl phenols, and phenol ethers from the di- and trihydroxyphenols, which would not move. A second development, a t a right angle to the first, with water-acetic acid, would separate the trihydroxyphenols from the dihydroxyphenols and give further indication of the compounds separated with cyclohexane-acetic acid. Thus the primary development would move the Cralkyl phenols furthest and the C1alkyl phenols least, with the qualification that the ortho isomers would move with the next higher homologs and 4-npropylphenol, carvacrol, and isoeugenol would not separate. In the second development the order of development would be reversed, with the Csalkyl phenols moving least and the Cla.lky1 phenols moving most. Then, the
Table 111.
Separation of Phenols in Mixtures" R , Valuns at 24' C.
Solvent. 7% acetic Solvent. 10% acetic acid in cycloacid in hexane water
Mixture of Phenols Phenol 0.07 0.58 o-Cresol 0.23 0.47 m-Cresol 0.14 0.47 o-Ethylphenol 0.34 0.34 Carvacrol 0.60 0.18 Guaiacol 0.14* 0.45 Eugenol 0.77 0.37 Isoeugenol 0.67 0.23 1-Naphthol 0.l o b 0.09 Phenol 0.08 0.57 o-Cresol 0.22 0.47 m-Cresol 0.14 0.47 +Ethylphenol 0.33 0.34 Carvacrol 0.59 0.18c Eugenol 0.77 0.38 Isoeugenol 0.67 0.22c p-Cresol 0.13* 0.46 Pn-Propylphenol 0.32 0.20" Carvacrol 0.59 0 . 18c 0.10* 0.09 1-Naphthol a Separations made on aper containing approximately 10% of Nyyon 66. Proportion of nylon not measured carefully. b While spots of 1-naphthol overlap those of guaiacol or p-cresol, they are readily distinguished by their p e t e r density of color. Pairs of spots overlapped extensively. ~~
VOL. 33,
NO. 7, JUNE 1961
841
ortho isomers should separate from the next higher homologs. This order of two-stage development is to be preferred to the reverse order, because the cyclohexane-acetic acid solvent provides more discrete spots. Alternatively, it would be possible to develop the monohydroxyphenols with cyclohexane-acetic acid on one paper strip and move them a considerable distance on a second strip with the same solvent. Then di- and trihydroxyphenols could be developed on the second strip with the water-acetic acid system. Preliminary diagnosis of some unknown mixtures could also be derived by comparing the development provided by the two solvent systems upon
separate papers. Then the reversed order of development of the homologous alkyl phenols could be observed relative to one or two known compounds. Finally, heavy papers impregnated with polyamides might provide a convenient alternative to the powdered polymer for the separation of larger quantities of phenols. ACKNOWLEDGMENT
The authors acknowledge the technical assistance of J. M. D'Estimauville.
(2) Carelli, V., Liguori, A. M., Mele, A,, Nature (London)76, 70 (1965). (3) Chang, W. H., Hossfeld, R. L., Sandstrom, W. M., J . Am. Chem. SOC. 74,5766 (1952). (4) Grassmann, W., Hormann, H., Hartl, A., Makromol. Chem. 21, 37 (1956). (5) Hossfeld, R. L., J. Am. Chem. SOC. 73,852 (1951). (6) HudeEek, S., Chem. lGty 49,60 (1955). (7) Mac&k, ,€I., Kubeh, J., Collection Czechoslov. Chem. Communs. 25, 301 (1960). (8) Rayburn, C. H., Harlan, W. R., Hanmer. H. R., ANAL.CHEM.25, 1419 (1953). ' (9) Schleede, D., Brennsto$-Chem. 36, 7 8 (1955). (10) Schlogl, K., Siegel, A., Mikrochemie ver. Mikrochim. Acta 40,202 (1953). \ - - - - I
LITERATURE CITED
(1) Bielenberg, W., Fischer, L., BrennstofChem. 23, 283 (1942).
RECEIVED for review October 12, 1960. Accepted March 13, 1961.
Separation of Some Fluorocarbon and Sulfur-Fluoride Cornpounds by Gas-Liquid Chromatog ra phy R. H. CAMPBELL and B. J. GUDZINOWICZ Special P rojecfs Department, Research and Engineering Division, Monsanfo Chemical Co., Everett, Mass.
acid 8114) to be the most effcctive for the gas-liquid partition chromatography of fluorocarbons. Dresdner et al. (2) also employed this Kel-F ester and hexadecane t p analyze 6- and 12-carbon fluorocarbon derivatives of sulfur hexafluoride. Ellis, Forrest, and Allcn (3) used columns packed with 50% by weight of grade 10 Kel-F oil on 30- to 60-mesh Fluon powder to separate corrosive inorganic compounds such as ClF, IIF, Clz, ClFa, UFs, and I3r2. Nitrogen trifluoride and CF, mixtures were investigated by Nachbaur and Engelbrecht (7) using moist silica gel with hydrogen as carrier gas a t 0" C.
Recent exploratory studies of reactions between fluorocarbons and sulfur-halide compounds required an efficient rapid method for the separation and characterization of the reaction products. A combination of gasliquid chromatographic and infrared spectrophotometric techniques adequately fulfilled the analytical requirements of these investigations. Furthermore, the feasibility of resolving mixtures of low molecular weight fluorocarbons and such sulfur-fluoride compounds as SF4, SFe, Soh, and SzFlo was demonstrated.
R
ECENT EXPLORATORY STUDIES Of
reactions between fluorocarbons and sulfur-halide compounds required an efficient rapid method for the separation and characterization of the reaction products. A literature survey revealed few publications on gasliquid chromatographic analyses of fluorocarbons and none for mixtures of low molecular weight fluorocarbons and sulfur-fluoride compounds such as SF4, SFe, SOFZ,, and SzFm However, the literature search did reveal some published works on related problems which indicated the chromatographic resolution of such mixtures to be possible. Hall et at. (6) noted that stationary liquid phases such as benzyl ether and diisodecylphthalate were both equally effective for the separation of ethyl ether and fluothane (2-bromo-2-chloro842
ANALYTICAL CHEMISTRY
I
I
1
1
I
0 8 6 4 2 RETENTION TIME, MINUTES
Figure 1. Gas chromatogram of typical components in SF&I production
1, 1,l-trifluoroethane). Using a column packed with activated alumina and hydrogen as carrier gas, Foulletier and Elchardus (4) resolved chlorofluorinated hydrocarbon mixtures of CCL, CClzFz, and CCIF1. Percival (8) found both di-n-octylphthalate and alumina satisfactory for the separation of Freon gases. Reed (9) evaluated the resolving power of a number of stationary liquid phases and reported Cl(CF2CFCl)p CFzCOOCzHa(the ethyl ester of Kel-F
APPARATUS AND REAGENTS
The gas chromatographic instruments employed for these investigations were the Perkin-Elmer Model 154B and 154C Vapor Fractometers with helium (Airco) as the carrier gas. Furthermore, since these chromatographs can accommodate two columns in series, it was possible to test several combinations of column packings simultaneously. In addition to the standard PerkinElmer 6 feet long by inch in diameter column A containing diisodecylphthalate as liquid stationary phase used in this work, the 6-, 9-, and 20-foot by 1/4-inch copper columns were packed with 33% by weight grade No. 3 Kel-F polymer oil (Minnesota Mining and Manufacturing Co.) loaded on 35- to 80mesh Chromosorb W (Johns-Mandle Co.). To prepare this column material, sufficient Kel-F oil was weighed, dis-
