LITERATURE CITED
(1) Badger, G. M., Donnelly, J. K., Spotswood, T. M., J . Chromatog. 10,
397 (1963). (2) Boubel, R. W., Ripperton, L. A., Presented a t the 56th Annual Meeting of APCA, June 9-13, 1963, Detroit, Mich. (3) Commins, B. T., Analyst 83, 386 (1958). (4) Cooper, R. L., Ibid., 573 (1954). (5) Monkman, J. L., Moore, G. E., Katz, M., Am. Ind. Hyg. Assoc. J . 23, 487 (1962). (6) Pavelka, F., D’Ambrosio, A., “Centro Provinciale per lo Studio Sugli Inquinamenti Atmosferici,” Amministra-
aione Provinciale Di Milano, pp. 111129 (1959). (7) P.’H. S . Publication No. 978, “Air Pollution Measurements of the National Air Sampling Network. Analyses c$ Sus ended Particulates-1957-1961, U. Govt. Printing Office, Washington, D. C., 1962. (8) Sawicki, E., Cassel, K., eds., “Symposium on the Analysis of Carcinogenic Air Pollutants,” Kational Cancer Institute Monograph No. 9,” U. s. Govt. Printing Office. Washinnton. 1962. (9) Sawiciki, E., ’Elbert, @. C., Hauser, T. R., Fox, F. T., Stanley, T. W., Am. Ind. Hyg. Assoc. J . 21, 443 (1960). (10) Sawicki, E., Elbert, W. C., Stanley, T. W., Hauser, T. R., Fox, F. T., ANAL.CHEY.32,810 (1960).
f
111) Sawicki. E.. Elbert. W. C . . Stanlev. ‘ T. W., Hauser,’T. R., Fox, F T T.i&zte&: J . Air Pollution 2, 273 (1960). (12) Sawicki, E., Hauser, T. R., Elbert, W. C., Fox, F. T., Meeker, J. E., Am. Ind. Hyg. Assoc.’J.23, 137 (1962): (13) Sawicki, E., Hauser, T. R., Stanley, T. W., Intern. J . Air Pollution 2, 253 (1960). (14) Tabor, E. C., Hauser, T. R., Lodge, J. P., Burtschell, R. H., A. M . A . Arch. of Ind. Health 17, 58 (1958). (15) Wieland, T., Liiben, G., Determann, H., Experientia 18, 430 (1962). RECEIVEDfor review August 26, 1963. Accepted Novemher 19, 1963. Division of Water and Waste Chemistry, 145th Meeting, ACS, New York, N. Y., September 1963.
Paper Chromatographic Separation, Identification, and Determination of DigIyceroIs HERBERT SIEGEL and A. B. BULLOCK
Shell Development Co., Emeryville, Calif. G. B. CARTER Industrial Chemicals Division, Shell Chemical Co
-
-
b a,a’ Diglycerol (3,3’ oxydipropanediol) and a,P-diglycerol (2,3’oxydipropanediol) have been identified b y paper chromatography as byproducts from glycerol processing. Diglycerol concentrates contained as many as four unknown a-glycols in addition to glycerol and the two identified diglycerols; these are presumed to be higher polyglycerols. A method i s described for determining a,a’-diglycerol in the presence of glycerol and other polyglycerols b y separation on a paper chromatogram and correlation of the area of the resulting spot with those obtained from known concentrations of a,ddiglycerol. The relative standard deviation) of the method i s f 10% and the relative error appears to be within A 10%.
P
often occurs during glycerol processing, leading to diand higher polyglycerols as significant by-products. The particular species formed have not been adequately identified because of difficulties in separation and the lack of pure compounds for reference comparison. Istin (5) employed a lengthy fractional vacuum distillation procedure for partial separation of polyglycerols. Others converted the polyols to more volatile derivatives, such as acetates (15), allyl ethers ( I S ) , and ketals ( I S ) to facilitate distillation. Wittcoff, Roach, and Muller (14) studied polyglycerol mixtures and reported syntheses OLYMERIZATION
502
ANALYTICAL CHEMISTRY
., Deer Park,
Tex.
of a,a’diglycerol (3,3’-oxydipropanediol) but did not mention the possibility of other isomers, such as a,pdiglycerol (2,3’-oxydipropanediol). This paper summarizes a paper chromatographic study of commercial diglycerol concentrates in which the a , d - and a,@-diglycerol isomers were separated and identified, for the first time to our knowledge. As expected, the linear a,a’-diglycerol was the principal isomer formed. The identifications were based on the chromatographic behavior of the pure compounds, which were synthesized unequivocally by an osmium tetroxide-catalyzed hydroxylation reaction. I n addition to the two diglycerols, four unknown materials containing a-glycol groups were also separated and detected. These substances are believed to be polyglycerols higher than the dimer The relation between concentration and spot area of a compound separated by paper chromatography provided the basis for the procedure, outlined below, for determining a,a’-diglycerol in the presence of other polyglycerols and glycerol itself. EXPERIMENTAL
Apparatus. Planimeter. Whatman No. 3 MM chromatographic paper, 8 inches wide by 2O3/4 inches long, with the length cut parallel to the machine direction of the paper. Two pencil lines are drawn across the width of the paper, 3 and 33/4 inches, respectively, from one end. The 33/4-inch line is marked with five pencil points, evenly
spaced and consecutively numbered’ The paper chromatogram is folded at the 3-inch line with the pencil lines facing outward. This fold supports the paper chromatogram in the chromatographic chamber for descending development. The 3-inch t a b is dipped into the solvent. Reagents. a , a f -and a,p-diglycerol were synthesized b y Fischer and Holm (2) in this laboratory. a,a’-Diglycerol was made by the hydroxylation of a-glyceryl allyl ether (3-allyloxy-1 ,2propanediol) with hydrogen peroxide using osmium tetroxide as a catalyst in a manner analogous t o previously reported work ( 8 ) . a,P-Diglycerol was made by applying the same hydroxylation reaction to @-glyceryl allyl ether (2-allyloxy-1,3-propanediol). The a,a‘diglycerol was recovered from the hydroxylation reaction mixture as a distillate fraction boiling a t 191’ c. a t 0.2 mm. of Hg. The a,P-diglycerol was recovered as a distillate fraction boiling at 189’ C. a t 0.1 mm. Analyses of these preparations, summarized in Table I, indicate they were better than 95% pure. a-Glycerol allyl ether is available commercially from the Shell Chemical Corp. It was purified by distilling and collecting the fraction which came over at 110’ to 111’ C. at 0.5 mm. of Hg. @-Glycerolallyl ether was synthesized by Van Winkle (12) in this laboratory. Epichlorohydrin reacted with allyl chloride to produce allyl 1,3-dichloro-2propyl ether, which was subsequently hydrolyzed with sodium acetate reagent to P-glycerol allyl ether. The product mas purified by distillation, and that fraction, which came over a t 116’ c. at 4 mm. of Hg, was collected.
ala'-Diglycerol standard solutions, aqueous, with concentrations of 3, 5, and 8 pg. per 11. Procedure. The procedure outlined below is for >;he quantitative determination of a a'-diglycerol in polyglycerol mixtureE containing glycerol and a,b-diglycerol. The paper chromatographic conditions described were also used for the qualitative resolution of polyglycerol mixtures. Run duplicate paper chromatograms for each sample. To points 2 and 4 on the chromatogram, apply 5-111. aliquots of the sample; to points 1, 3, and 5, apply 5-p1. aliquots of each of the ala'diglycerol standard solutions. Use a single 5-p1. self-filling pipet (Microchemical Specidties Co., Berkeley, Calif.) to apply the sample and standards. Touch the tip of the pipet to the paper and allow the pipet to drain with the aid of the sorptive properties of the paper. The 5-p1. sample si:se applies to samples having a,~~'-diglycerolconcentrations within the range of 3 to 8 pg. per pl,. The best results were obtained with samples in which the a$-diglycerol concentrations were lower and the glycerol content was a b o i t 100 pg. per pl. If the sample is m x e concentrated, prepare suitable dilutions. If the sample is more dilute, apply the sample in successive 5-pl. aliquots, allow each aliquot to dry thorouphly before applying the next. Develop the pap1:r chromatogram with 1-butanol satupated with water for 40 hours, using cescending solvent migration in an atmosphere saturated with the 1-butanol-sat urated-with-water
t
P
I 1
I
0 . 2
1
Conccnliamn
I Of 0 , -
I 5
I
I b
I 7
B
I 9
1
ala'-diglycerol in the sample. The results from duplicate chromatograms should not differ by more than 1.5 pg. per ~ 1 . Heat chromatograms sprayed with the aqueous ammoniacal silver solution (3) in an oven a t 80° C. for 30 minutes to 1 hour. At the end of this time, immerse the chromatogram in a 2.5% aqueous sodium thiosulfate solution for 15 minutes. Polyols appear as dark gray spots on a light gray background.
0
-Dlllycerol. m>crogrsms mlelOllter
Figure 1. Comparison of spot areaconcentration curves from three chromatographs of apt-diglycerol
solvent, allowing solvent to drip off the end of the chromatogram. -4t the end of the 40 hours, spray the air-dried chromatogram evenly with 0.001M aqueous sodium periodate solution. Avoid excess spray, because it distorts the ala'-diglycerol spots. After 6 minutes, spray with a benzidine solution. Compounds containing a-glycol functional groups appear as white spots on a blue background (1). Outline the white spots corresponding to ala'-diglycerol with an indelible pencil as soon as they appear. Measure the area of each spot in duplicate with a planimeter. Plot the areas of the ala'-diglycerol spots from the standard solutions against the logarithms of the corresponding concentrations. Draw the best straight line through the plotted points (Figure 1). bverage the areas of the ala'diglycerol spots from the sample. -4pply this average to the calibration curve to obtain the concentration of
RESULTS
Separation of Diglycerol Concentrates. The paper chromatographic separations of the diglycerol concentrates, sold by the Colgate-Palmolive Co. and the Eastman Kodak Co. are summarized in Table 11. The Colgate-Palmolive material is a byproduct from the glycerol process involving the saponification of fats to soaps; the Eastman source is believed, but not definitely known, to be a soap-glycerol process. Several components were found in each diglycerol concentrate. Glycerol, a,a'-diglycerol, and alp-diglycerol were identified in both materials by comparison with the migration distances of the respective model compounds. For unexplained reasons, a,@-diglycerol appeared as a streak, rather than a well defined spot, on the chromatogram of the Eastman diglycerol. Two unidentified components, migrating a t Rn values of 0.54 to 0.57 and 0.36 to 0.38, were detected in both diglycerol concentrates.
I. !Summary of Analytical Results for a,d- and a#-Diglycerols Boiling point, Refractive cy-Glycol value,' Hydrogen, wt. % ' moles/100 g. "C./mm. index, -Carbon, wt. % Hg nD20 Theory Found Theory Found Theory Found Table
Moleculr,r weip;ht, calcd.
Compound 43.36 166.2 191/0.2 1.4899 a,a'-Diglyceml 43.36 a,B-Diglycerol 166.2 189/0.1 1.4898 a Oxidation with sodium periodate ( 7 ) . Acetylation with acetic anhydride ( 7 ) . Hydroxyl value of cy,p-diglycerol not determined.
'Table It.
Material Glycerol CY, cy'-Diglycerol a,p-Diglycerol Eastman diglycerol, technical Colgate-Palmolive diglycerol, technical Rc
+0 ==
1 1.00
8.5 8.1
1.20 0.602
0.75
...
...
... ...
Streak
0.79
0.54
0.36
0.89
0.77
0.57
0.38
1.00
0.84
1.15 0.588
eq./100 g.
Theory
Found
2.41 2.41
2.38 c
Separations of Diglycerol Concentrates
... ... ...
1.01
...
8.49 8.49
R G of~ components detected on finished paper chromatograms 2 3 4 5 6
... ...
...
43.4 44.3
Hydroxyl value, *
...
7
Detection reagent PeriWhatrnan Ammo- odatebenpaper niacal So. silver zidine
...
...
...
1,3MM 3 MM 3 MM
...
...
0.31
0.25
(Streak)
++ +
1
++ +
Ob
3 MM
0
+
+b
distance migrated by compound on paper chromatogram distance m
