ple which contained some dodecanol. The plot of A (sq. mm.) against z gave a straight line. By applying the least square method, a n empirical Equation 3 was derived. A = 42.1
+ 19.0 X 1 0 2 x
(3)
Recovery was calculated by putting the respective peak area into Equation 3. Satisfactory coincidence is observed between the first and third columns in Table 11. By comparing Equations 1 and 3, we get a --a-
1
42.1 19.0 x 102
The dodecanol content in the original sample is thus estimated to 2.17%. Mesityl oxide and phorone are possibly produced in the decolorization process of MP1-12. The solvent, acetone, may be polymerized by the catalytic action of hydrogen chloride ( I ) , which is probably included in active charcoal. The third peak in the chromatogram had the same R.R.V. as that of phorone, and became larger with the addition of phorone. The phorone content was estimated t o l.43To by a calibration curve. Both of the dodecanol and phorone peaks disappeared when the sample was allowed t o flow down in a thin film through a molecular distillation apparatus under high evacuation. This sample seems to be quite pure, because no impurity was detected by paper and gas chromatography. Peak areas of phorone added to thus purified sample are listed in Table 111. The A-x relation can be expressed by A = -1.3
+ 19.95 X 10%
(4)
Equation 4 practically passes through the origin. The deviation is within the limit of expeiimental error. The recovery is quantitative, as shown in the third column. MPd-12. Raw MPd-12 showed a peak corresponding to 1-decanol. After the flow-down through a molecular distillation apparatus, howeve;, xo impurities were detected either by paper chromatography or b y gas chromatography.
Table 111. Peak Area of Phorone Added to the Purified MPl -1 2
Weight Fraction of Added Phorone, x, X
lo-’
0.00 1,745 4.37 6.51 10.29
1526
Peak Area, A , S q . Mm. 0.0 32.0 85.5 129.2 204.0
Recovery Calcd. by Eq. 4, 10-2 0.06 1.67 4.35 6.54 10 29
x
ANALYTICAL CHEMISTRY
Commercial Nonionic Detergents. A peak corresponding to dodecanol was observed in t h e gas chromatogram of a commercial nonionic detergent, Brij 30, whose composition is polyoxyethylene dodecyl ether and average oxyethylene number is about 3 [H.L.B. = 9.5; H.L.B. stands for Hydrophilic Lipophilic Balance proposed by Griffin ( 5 ) ] . The calibration curve for dodecanol was linear and gave a dodecanol content of 8.9%. When mono-, di-, tri-, or tetraethylene glycol was added to Brij 30, a peak appeared at the respective R.R.V. None of these peaks was observed on the original chromatogram of Brij 30. Accordingly, the absence of mono- to tetraethylene glycols is concluded. On the other hand, the paper chromatogram showed that Brij 30 contained some PEG’S of higher molecular weight. I n the gas chromatogram of Brij 30 appeared another peak whose R.R.V. was 2.4. This peak was ascribed to ethylene glycol monododecyl ether by its intentional addition. The gas and paper chromatograms of Brij 30 have thus revealed that it contained dodecanol, ethylene glycol monododecyl ether, and P E G containing more than four oxyethylene units. A similar gas chromatogram of Brij 35, which contains 17 oxyethylene units on the average (H.L.B. = 16.9), has proved the absence of long-chain alcohols and P E G having one to four oxyethylene units. P E G of higher molecular weight was detected on the paper chromatogram. Kikkol BL-4.2 (polyoxyethylene dodecyl ether having two oxyethylene units on the average) has shown similar patterns to those of Brij 30 on both the gas and paper chromatograms. Dodecanoi content was estimated to 9.8%. I n all of the above three detergents, mono- to tetraethylene glycols mere not found, whereas higher PEG’S were detected. These detergents are synthesized by blowing ethylene oxide into dodecanol, and polyethylene glycol can form along with the detergent if water is present during synthesis. The absence of the lower homologs may be due to the higher reactivities of water and PEG than those of dodecanol and its oxyethylene derivatives, or to any purification process which eliminates these lon-er homologs. Retention Volumes of Lower P E G and Its Derivatives. There is a linear relationship between the number of carbon atoms and the logarithm of retention volume in each homologous series of fatty alcohols, acids, and esters (9, 6, 9). The retention times of mono- to triethylene glycols have been reported to increase with the number of oxyethylene units (4). In order to examine the quantitative relation between the retention volume and the
number of oxyethylene unita in PEG, the logarithms of R.R.V.’s of mono-, di-, tri-, and tetraethylene glycols listed in Table I were plotted against their oxyethylene numbers. The graph shows a linear relation. The same relationship is found also in mono- and dimethyl ethers of PEG. Comparing these three homologous series at the same oxyethylene number, the R.R.V.’s decrease in the order P E G > monomethyl ether > dimethyl ether. This order is concordant with that of boiling point. Substitution of OH group by OCH, decreases R.R.V., but its effect becomes smaller with the length of oxyethylene chain as evidenced by the approach of three lines. ACKNOWLEDGMENT
The authors acknowledge the suggestions and discussion of Eric Hutchinson and Ichiro Ishizuka. LITERATURE CITED
(1) Claisen, L., Ann. Chem. Liebigs 180. 1 (1875). (2) Cropper, F. R.,Heywood, A,, “Symposium on Vapour Phase Chromatography,” Institute of Petroleum, London, May/June 1956. (3) Ginn, M. E., Church, C. L., Harris, J. C., ANAL.CHEM.33, 143 (1961). (4) Ginsburg, L., Ibid., 31, 1822 (1959). ( 5 ) Griffin. W. C.. J . Soc. Cosmetic Chem‘ ists 1, 311 (1949); Am. Perfumer Essent. Oil Rev. 6 5 , No. 5, 26 (1955). (6) James, A. T., Martin, A. J. P., Biochem. J . 50, 679 (1952). (7) Nakagawa, T., Nakata, I., J Chem. SOC.Javan. Ind. Chem. Sect. 59. 709 (1956). (8) Nakagawa, T., Tori, K., Kolloid-2. 168. ~-~ 132 (1960). ( 9 ) Ray, N. H . , J . A p p l . Chem (London) 4 , 21 (1954). .
-.
I
\ - - - - , -
RECEIVEDfor review March 30. 1961. Accepted J u n e 16, 1961.
Correction Water Analysis In this article by M. W. Skougstad and M. J. Fishman [ANALCHEM.33, 138R (1961)], on page 155R, column 1, last paragraph, the method summarized is that of J. P. Riley, Anal. Chim. Acta 9, 575 (1953). The method of Crowther and Large does not involve heating, nor does i t incorporate manganous sulfate. On page 155R, column 2, lines 1 and 2 should be changed to “The absorbance is directly proportional to nitrogen content u p t o 4 pg. per ml.” On page 163R, column 2, reference (3P), IGO BM/S-07 should be changed to IGO TM/S-07.
