Primary Amyl Alcohols Determined by Gas Chromatography PETER J. PORCARO and V. D. JOHNSTON Analytical laborafory, The Givaudan Corp., Delawanna, N. J.
b A gas chromatographic method is offered to determine the weight percentages of mixtures of primary amyl alcohols using the commercial detergent Tide as the column packing. This method is rapid and reproducible. It is offered for fast routine use to suppliers and consumers alike, as well as an additional means to investigate fusel oil further. Tide should also be useful for chromatographic separation of similar materials. of primary amyl alcohols are usually determined spectrophotonietrically in the infrared region. The results obtained photometrically are subject to the usual limitations associated with ternary or more complex mixtures. The analytical bands must be distinguishable and the mixture must be free from interfering materials. The calculations with matrix application can, of course, be burdensome. The authors have consulted with various industrial laboratories and with suppliers of primary amyl alcohols (1, 5 ) and found that a more direct method would be preferable. Gas chromatographic attempts to date have been limited by their inability to distinguish 2-methyl-1-butanol (active), b.p. 127.5' to 127.8' C., from 3methyl-1-butanol (primary isoamyl), b.p. 130.6' to 131.6' C. ( 7 ) . This is surprising considering their relatively wide boiling points. 1-Pentanol (primary normal), b.p. 137.8' C., is easily separated. 2,2'-Dimethyl- 1-propanol, b.p. 113' to 114' C., is the other possible primary (4); however, this material is of no practical interest. No attempt nas made to identify it in the light impurities 1% hich also contain traces of butyl alcohols. A stationary phase was sought which would separate 2-methyl-1-butanol from 3-methyl-1-butanol. Apieson L (James G. Eiddle Co.), silicone rubber (F & R.1 Scientific Corp.), Dow-Corning silicone oil No. 550, and Carbon-ax 20M (Union Carbide Chemicals Co.) on acid-washed Chromosorb W were tried but did not separate 2-methyl-1-butanol from 3-methyl-1-butanol. Tide (commercial alkylaryl sulfonate mixture, IXTURES
Procter and Gamble) proved to be successful. Tide and similar detergents have been the subjects of investigation for use as a solid support with various substrates (2) and as a general purpose packing (3, 6). After a preliminary treatment, Tide nas useful not only for mixed primary amyl alcohols but also for other materials of commercial importance in the perfume and flavor industry--vis., niethylionone isomers, terpene alcohols, etc. l l a n y amyl alcohol esters are widely used commercially. Since the properties of the esters depend on the proportions of the isomeric alcohols, it is necessary to know the exact composition of the amyl alcohol processed so the most desirable grade can be selected. Several commercially available primary amyl alcohol mixtures were, therefore, analyzed. EXPERIMENTAL
Apparatus. A Model 202 F & hf Scientific Corp. programmed chromatograph. was used. Instrument Parameters. Column, Tide, 21 feet (l/rinch O.D. copper tubing); temperature, 160' C.; gas flow, 15 ml. per minute inlet, 30 ml. per minute outlet; gas, helium; sample size, 1 PI.; chart speed, 0.5 inch per minute; bridge voltage, 9 volts; current, 12.5 ma.; attenuation, 16 mv.; detectors, 100,000-ohm thermistors; air peak elution, 3.2 minutes. Column Preparation. Tide purchased in the New York metropolitan area was heated in a drying oven a t 110' C. overnight, principally to evaporate the perfume and moisture. ,4 screened sample of 40/60 mesh was carefully packed into the copper tubing and the desired length filled. Lengths varying from 10 to 21 feet were successfully employed. The tubes were wound into coils to fit into the oven of the chromatograph. The column was conditioned a t 200" C. for 5 hours before use, with the exit leg unconnected and helium slowly flowing.
commercial suppliers designated A, B, C, and D were determined (Figure 1). The designated elution time in minutes is printed above the peak, reading from left to right. Reference materials for calibrating elution times were obtained from Distillation Products Industries (D.P.1,) Pure 2-methyl-1-butanol, pure l-pentanol, and isoamyl alcohol containing 10 to 15% active 2-methyl-1-butanol as stated by the supplier, were obtained. A synthetic mixture of 50 parts by weight of 2-methyl-1-butanol in 50 parts of the isoamyl alcohol supplied by D.P.I. was chromatographed. These chromatograms are reproduced in Figure 2. The weight percentage composition was calculated using the rectangular method of geometric approximation which utilizes retention time times peak height (Table I). This method of calculation is preferred because of the slight tailing tendency of the alcohols. The results obtained vere 15% higher than weighed into the mixture. The D.P.1.-supplied isoamyl alcohol, therefore, contains 15% active 2-methyl-1-butanol. The synthetic mixture prepared abo\e was determined several times with a reproducibility of +0.5% for each componrnt. 1-Pentanol was not included in this mixture because there is
Table 1. Quantitative Results Obtained by Geometric Approximation
Keight % Isomer Distribution 231Methyl-1 Methyl-1 PenSupplier butanol butanol tanol A B
C
D
Standards, D.P.I.
49.0 70.5 15.0 34.5
100
44.3
1 5
84.0 4.5
61.0
28.0
..
...
...
1 0
RESULTS A N D DISCUSSION
The chromatograms of representative grades of primary amyl alcohols from
Isoamyl alcohol
15.0
84.5
VOL. 33, NO. 3, MARCH 1961
... 361
8
P.METHYL-I-BUTANOL
2 3-METHYL-I-BUTANOL
10.8 ~~.METHYL.I-BUTANOL
SYNTHETIC
PRIMARY ISOAMYL ALCOHOLS SUPPLIER
2- METHYL-I BUTANOL
SUPPLIER B
A
ISOAMYL ALCOHOL
-
PRIMARY AMYL ALCOHOLS
DPI
IO- I5%ACTIVE
DPI
)-METHYCI-OUTANOL
13.9
I I
SYNTHETIC MIXTURE ( D P I ) ISOAMYL ALCOHOL SUPPLIER
PRIMARY AMYL ALCOHOLS
C
SUPPLIER
D
362
ANALYTICAL CHEMISTRY
DPI
3- HETHY L- I-BUTANOL ( ISOAMYL 10-15 %ACTIVE)
Figure 1. Chromatograms of some commercially available grades of primary amyl alcohols
no problem separating it. Our main concern was the effectiveness of separation of 2-methyl-1-butanol (active) from 3-methyl-1-butanol (isoamyl) in a column which could be used over a broad temperature range (room temperature to 250’ C.) and exhibit an ability to chromatograph usefully the many complex mixtures in our perfume and flavor industry.
I-PENTANOL
2-METHYL-I-BUTANOL
Figure 2. Chromatograms of reference materials used for calibration
LITERATURE CITED
(5) Farinella, F. C., Bel1 Chemical Co., nrivate communlcatlon, November 25,
(1) Burgess, J. A., Union Carbide Chem-
icals Co., private communication, April 27, 1960.’ (2) Decora, A. W., Dinneen, G. U., ANAL. CHEM.32,164 (1960). (3) Desty, D. H., Harbourn, C. L. A., Zbid., 31,1965 (1959). (4) Encyclopedia of Chemical Technology, Vol. 1, p. 845, Interscience, Xew York, 1960.
Meeting. ACS; Dal 1956. (7) Kuffner, F., Kallina, D., Monakh. Chem. 90,463-6 (1959). -r
RECEIVEDfor review July 27, 1960. Accepted December 5, 1960.
