Gas Chromatographic Study of Some Chlorinated Hydrocarbons PAUL URONE, JOHN ELVANS SMITH,' and RICHARD J. KATNIK Department of Chemistry, Universify o f Colorado, Boulder, Colo.
b
The gas chromatographic behavior
of 1 1 chlorinated hydrocarbons was studied on six columns and at four temperatures for possible qualitative and quantitative applications. Paraffin and Apiezon L columns gave good qualitative and quantitative performances. Peak area measurements were accurate to =?=0.02 pmole in the 0- to 5-pmole range. Carefully measured specific retention volumes made possible the calculation of partition coefficients, activity coefficients, and excess partial molar heats of solution. For column substrates with indefinite molecular weights, such as paraffin and Carbowax, relative activity coefficients were calculated.
T
HE GAS CHROMATOGRAPHIC BEHAVIOR of chlorinated hydrocarbons
has been the subject of a number of theoretical and applied studies. Purnell and Spencer (13) studied the properties of a number of liquid phases on kieselguhr using the chloromethanes. Pollard and Hardy (11) used various halogenated hydrocarbons to study separation and retention volume trends with various types of liquid phases and column conditions. Quantitative analysis was described as demanding a large degree of care and control. Harrison (6) reported retention volumes of some 25 halogenated hydrocarbons. The effects of changes in injection and katharometer temperatures and factors affecting peak heights were described. Green (4)analyzed chlorofluoromethanes and reported a linear relationship between peak height and sample volumes a t S T P with an accuracy of 1.5%. Haslam and Jeffs ( 7 ) applied gas-liquid chromatographic techniques to the qualitative and quantitative examination of solvents from plastic adhesives. The relative retention times of some 50 solvents were reported. Warren et al. (16) analyzed mixtures of chlorinated hydrocarbons. Typical analyses as well as retention times of 12 chlorinated hydrocarbons a t two f l o ~rates mere re-
1 Present address, U. s. Kava1 Research Laboratory, Washington 25, D. C.
476
ANALYTICAL CHEMISTRY
ported for a paraffin on Celite 550 column. I n investigating methods of applying gas chromatographic techniques to the measurement of chlorinated hydrocarbon vapors in air (15), i t became necessary to study the behavior of these compounds in somewhat greater detail. This paper reports the data obtained and some of the deductions derived from the study. Eleven Chlorinated hydrocarbons were selected for the frequency of their industrial use as well as their potential toyicity to the human system. Fully corrected retention volume data for these as well as for a number of industrially related solvents were determined on six columns a t two to four temperatures. I n addition, quantitative curves based upon both peak height and peak areas for selected members of the group gave a system of quantitative gas chromatographic analysis in the concentration ranges to be encountered in air contamination studies. .4 6-foot column of paraffin wax operating a t 97" C. effected excellent separation and resolution upon a mixture of the 11 chlorinated hydrocarbons, and columns of ,4piezon L high vacuum grease and Halocarbon stopcock grease gave good performance with respect to the chlorinated solvents. Columns of tritolyl phosphate (TTP), Carbowax 4000, and Carbowax 2011 were marginal in performance. The partitioning properties of the tn-o Carboivaxes were almost identical, and their ability to effect elution of the solutes out of line with the pattern established by the other columns was of interest and of practical importance. Silicone oils 550 and 710 proved somewhat unsatisfactory with respect to the resolution of the loner boiling compounds. A column made nith a liquid detergent (Triton X-100) was highly unsatisfactory. EXPERIMENTAL
G a s Chromatograph. h Beckman Rlodel GC-2 gas chromatograph equipped with a filament wire thermoconductivity cell and a 1-mv., 1-second recorder was used throughout the study. Helium was used as the carrier gas, and a soap bubble
flowmeter was used to measure t h e flow rate. Columns. All columns were made of coated (2-22 firebrick or Chromosorb packed into 6 feet b y '/* inch O.D. copper tubing with the exception of the silicone 550 column which was made of stainless steel tubing of t h e same dimensions. ~ ~ P I E Z OL. N 4.58 grams on approximately 13.3 grams of 30- to 60-mesh Chromosorb. CARBOTAX4000. 4.38 i 0.09 grains on approximately 13.1 grams of 35- to 80-mesh C-22 firebrick. CARBOW.AX 2011. 4.37 A 0.09 grams on approximately 13.1 grams of 35- to 80-mesh C-22 firebrick. HALOC.4RBON GREASE. 4.52 grams on 13.42 grams 30- to 60-mrsh Chromosorb. PARAFFIN KAS 4.58 grams on 13.93 grams of 30- to GO-mesh Chromosorb. TRI-TOLYL PHOSPHATE (TTP). 4.46 grams on 13.71 grams of 30- to 60-mesh Chromosorb. Method. I n most cases, injection was made with a 10-pl. syringe. Care was used to inject rapidly and to avoid heating the syringe needle. Retention volume data were obtained with a minimum of two individual 5 0-pl. injections of each compound a t each temperature. Inlet helium pressures were measured with a mercury manometer attached a t the injection port, and outlet pressures were assumed to be equal to the prevailing barometric pressures n hich a t this altitude were in the vicinity of 630 mm. Bridge current was kept a t 250 ma., and column temperatures were reproducible to &0.lo C. Flon- rates were constantly checked with a 50-ml. soap bubble flowmeter to the nearest 0.1 second. The vapor pressures of the chlorinated hydrocarbons were taken either directly from tables in Jordan (9)or were extrapolated from available data by means of log vapor pressure us. 1/T curves. Quantitative data were obtained from 0.005 to 1.0M solutions of the chlorinated hydrocarbons in toluene, o-xylene, and/or is0 - octane. Peak heights were measured to the nearest 0.01 inch. Peak areas nere measured both by the peak height times the width at half-height method and by a planimeter. KO significant difference m-as found in the tmo methods. Specific Retention Volumes. Specific retention volumes a t column temperatures were calculated accord-
9
measured by the expression (19): K = V$/V,,, , where V L , ~is the volume of the liquid phase. Since the specific retention volumes (T';) sho\T n in Table I are corrected retention volumes a t the column temperatures per gram of liquid phase, they need only be multiplied by the density of the liquid phase, p, at the given temperature to obtain the partition coefficients-i.e., K = Vip. The densities of some of the liquid phases were determined in the laboratory a t 74'14" in grams per cubic cm. as follows: paraffin, 0.768; Apiezon L, 0.859; TTP, 1.128; Carbowas 4000, 1.081; and Carbonax 2011, 1.080. HoweTer, in as much as the densities of many organic liquid phases range in the vicinity of 1 i 0.3 grams per cubic cm., the specific retention volumes such as those given in Table I may be taken as a first order approximation of the partition coefficients. Temperature Effects. Log V i us. 1/T plots for each of the compounds gave straight, approvimately parallel lines for t h e -4piezon L (Figure I ) , TTP. and C a r b o r a x columns. A t 50" C., t h e TTP column sholTed a sharp increase in retention volumes, while the Carbowas columns showed a sharp decrease. T h e latter effect was probably due to the fact that the Carbowax was no longer a liquid at 50" C. The log V i us. 1, T plots for the paraffin and halocarbon columns tended
ing to equations given in the literature (1-3).
Table I lists the values for the chlorinated hydrocarbons on the various columns a t the temperatures studied. The retention volumes as well as the resolution of the Carbornax 4000 and 2031 coluinns were almost identical. Consequently, only the 97" C. data for the latter are given. The specific retention volumes for benzene are given for comparison. Retention volumes were reproducible within 1 to 2%. Under ideal conditions, where all operations and observations are undertaken with rigid control, eweptional reproducibility can be achieved. Thus, a pure sample of CHCllCHClz put through the Apiezon L column a t 97" C. a t a pressure head of 937 mm. and a flon rate of 7 5 ml. per minute yielded a V %value of 1152 ml. The same compound, when injected in a mixture of all 11 chlorinated hydrocarbons, 2 days later, a t the same temperature but a t a pressure head of 833 mm. and a flow rate of 54 ml. per minute, yielded a V $ value of 1150 ml. The pressure a t the col~iiiin outlet in both cases n-as 630 mm. Within a t least a 50% variation of helium pressure and flon rate, the corrected retention volumes n ere essentially constaiit. Partition coefficients. I n gas chromatography, partition coefficients are Table I.
061
,yl2Y',
i97'
150' 1
174.
2 5
3c
I x io3 Figure 1. Variation of specific retention volumes of 1 1 chlorinated on an Apiezon L column with temperature Compounds a r e numbered according t o their increasing boiling points 1. CHpCIz 7 . CCIz=CHCI 2. CHClpCH3 8. CHClzCH2CI 3. CHCI8 9. CC12==CC1~ 4. CCIsCH3 10. CeHjCl 5. CCId 1 1. CHCIzCHClp 6 . CHzClCHpCl
Specific Retention Volumes ( V i ) for Some Chlorinated Hydrocarbons and Benzene on Various Columns a t Four Temperatures
Temperature,
"C.
CHpClz
CHC1,CH,
CHC13
50
38.2 29.5 17.0 8.08
71.7 51 .:3 29.3 14.2
109 74.3 41.5 1'3.6
74 97 125
CC13CH3 158 108
57.8 28.0
CC1, 212 141 76.5 34.5
CH,cc12= ClCHzCl CHCl PARAFFIN 142 306 93.9 189 51.3 98.2 23.4 42.6
CHClZCH&1
...
286 146 60.3
CC1,= CCl:!
...
568 273
105
CeHsC1
...
677 323 124
CHCIZCHC12
...
930 433 158
CsHe
...
136 74.3
...
LkPIEZOX L
50 74 07
125 50
74 97 125
29.5 14.8 8.08 4.58
523
26.0 14.0 7.65
83 8 40.4 21 .o 10.9
10.2 7.29 3.10 1.33
21.2 14.8 6.85 2.65
27.4 19.2 8.85 3 10
50 74 97 125
117 56.1 30.8 13.9
50
24.0
45.6 32.1 15.7 5.31
1T.9
311 137 68.5 29.6
202 96.3 51.6 24.2
52.1 138 59.3 24.2
19.2 57.1 28.5 13.5
58.4
27.4
151 ~~
71.8 38 1
74 97 125
31.9
13 5
18.1 54.8 26.3 12.1
97
30.9
25.2
69.6
115 53.5 29,5 14.4
153 72.1 37.1 17.9
111 50.2 27.3 13.1
125 101 51.3 22.9
HALOCARBOX GREASE 51.8 45.1 79.4 37.6 31 . O 53.1 18.1 13.7 24.3 5.97 4.64 7.51 TTP 209 426 400 99.8 190 181 52.7 93.2 92.0 24.7 40.3 38.8 CARBOWAX 4000 18.7 77.8 45.2 55.8 195 122 27.4 86.8 57.1 13.5 32.4 23.1 CARBOW.4X 2011 27.4 82.3 54.9 ~~
...
164 80.8 34.0
...
92.9 40.9 12.0
...
628 289 109
...
301 142
...
...
55.5
374 176 68.2
... 164 73.0 20.4
206 91.7 24.4
290 124 34.5
...
... 3065 1160 362
...
...
...
...
... 37.6 l!) .0
826 372 143
703 274
... 16.5 78.7 31.1
548 235 83.6
1090 283
263
77.8
239
1045
87.8
...
71 . O 37.1
03.5
359 170 69.5
...
...
557 251
...
... 133 69.4
...
... ...
VOL. 34, NO. 4, APRIL 1962
... 80.0
43.3
...
42.3
e
477
~
Table II.
~~
~
Activity Coefficients and Heats of Solution for Some Chlorinated Hydrocarbons on Various Gas Chromatographic Columns
Boiling point (760 mm.) Vapor pressure ( p ' , mm. H,g) 50 C. 74' c. 97" c. 125" C. Activity coefficient ( 7 ; ) TTP (74'))" D.X.P. (77")b Relative activity coefficient (V',PO at 74" CHClzCHs 1.00) Paraffin Apiezon L Halocarbon TTP Carboyax 4000 d(log 103 d(l/T) Paraffin Apiezon L Halocarbon TTP Carbowax 4000 AHv(kcal./mole) Paraffin Apieaon L Halocarbon TTP Carbowas 4000 A H , (kcal./mole, 760
CHzC1, 40' (1090) (2320) (4550) (9100) 0.45 0.46
CHCG CH3 57.4O
CHC13 61.2'
590 1280 2340 4400
518 1120 2130 4210
0.64
...
0.38 0.38
cc13-
CHs 74.1'
330 760 1500
3250
0.80
CClr 76.7' 315 705 1330 2700
CH, ClCH2-
c1
83.5' 235 555 1130 2380
cc1*=
CHCl 87.1' 215 512 1020 2130
...
0.84 0.71
0.56
0.55
0.63 0.55
0.80 0.82 0.78 1.26 1.62
0.66 0.65 0.72 1.31 1.78
1.20 1.19 1.10 0.87 0.65
0.68 0.64 0.70 0.99 1.12
1.68 1.60 2.15 1.62 1.68
1.62 1.57 2.20 1.58 2.10
0.47
65 175 395 840
40 112 '55 620
0.93
0.63
23 67 165 425 0.29
...
1.14 1.01 1.02 0.73 0.50
0.66 0.63 0.66 1.46
0.86 0.79 0.82 0.99
0 89
1.72 1.72 2.30 1.82 1.98
1.82 1.85 2.42 2.08 2.42
0.79 0.74 0.88
1.55 1.38 2.00 1.62 1.92
1.48 1.43 2.02 1.65 1.85
1.58 2.10 1.80 2.05
1.62 1.55 2.10 1.62 1.70
7.10 6.32 9.16 7.42 8.79
6.78 6.55 9.25 7.56 8.47
7.24 6.96 9.62 8.24 9.39
7.42 7.10 9.62 7.42 7.79
7.70 7.33 9.85 7.42 7.69
7.42 7.19 10.08 7.24 9.62
7.88 7.88 10.53 8.34 9.07
6.69
7.3
7.02
(7.96)d
7.17
7.7
7.6
1.52
445 LO50
CHC1,CeHjC1 CHCL 146' 132"
...
1.oo 1.oo 1.oo 1.00 1.oo
0.45
76 200
CCI,= CClz 121"
0.80
0.95 0.97 1.12 0.71 0.43
0.60
CHClr CHZCl 114"
...
1.05
0.97 0.45
1.14
.,.
1.98 1.98 2.42 1.92 1.98
1.98 1.92 2.50 2.08 2.25
2.08 2.08 2 50
8.34 8.47 11.08 9.53 11.08
9.07 9.07 11.08 8.79 9.07
9.07 8.79 11.45 9.53 10.31
c.53 9.53 11.45 11.45 10.44
8.8
8 .:3
8.7
8.8
2.43
2.50
2.28
mm.)o a
Tritolyl phosphate.
* Dinonylphthalate.
Determined by Hardy ( 6 ) . According to Rossini (fq). Determined at 13.4" C.
to have a slight amount of curvature dropping noticeably a t 50" C. In these cases, the slopes were taken as the best straight line through the 125", 97", and i4" points. I n all instances, the slopes of the lines of the more volatile compounds tended to be less than the slopes of the less volatile compounds (see Table 11). Since the lines were approximately parallel, there was no trend for a change in the order of elution of the compounds with a change in temperature. However, none of the columns eluted the compounds strictly in the order of either their boiling points or their vapor pressures. Figure 2 more clearly shows the relationship between the retention volumes and the vapor pressures of the 11 chlorinated hydrocarbons at 74" C. on two nonpolar columns, Paraffin and Apiezon L, and on two polar columns, TTP and Carbowax. I n general, the retention volumes decrease with increasing vapor pressure when plotted on a log/log basis (8). However, sharp positire and negative deviations from
478
ANALYT!CAL CHEMISTRY
a straight line are evident. Of interest are the similarities of the patterns of deviation of the columns of similar polar character and the contrasts of the patterns betn-een the columns of dissimilar polar character. For example, tetrachloroethylene, trichloroethylene, and carbon tetrachloride have relatively high retention volumes in the nonpolar Paraffin and Xpiezon L columns but low retention volumes in the polar TTP and Carboaas columns. Conversely, 1,1,2-trichloroetliane and 1,Zdichloroethane have low retention volumes in the nonpolar and high retention volumes in the polar columns. Chloroform shows only a slightly high retention volume in the nonpolar columns, but is definitely retained by the polar columns to give high retention volumes. l,l,l-Trichloroethane and 1,l-dichloroethane show approximately normal retention volumes in the nonpolar columns but low retention volumes in the polar columns. Hydrogen and pi bonding, polarizability, and complex covalent interactions are involved in these deviations
(3, 6). Hotvever, more detailed theoretical gas chromatographic studies are necessary t o evaluate more accurately these chemical and physical factors. At present, one is restricted to more generalized expressions involving thermal effects. Relative Activity Coefficients. I n gas chromatography, an activity coefficient of the solute a t infinite dilution can be calculated according to the following equation (3):
where M is the molecular weight of the liquid phase, p o is the vapor pressure of the solute, R is the gas constant, and the other terms are as defined above. The activity coefficient here incorporates the combined physical and chemical effects of the solvent upon the solute, For nonideal solutions, fugacities replace vapor pressures. The activity coefficients of the 11 compounds were calculated for the TTP column a t '74" C. and compared to the activity coefficients obtained by
AH? is the excess partial molar heat
of solution d(1og V,J/d(li T ) is equal to the slope of the line obtained by plotting log Vb us. 1/T (Figure 1). Table I1 lists both the slopes of the log V i us. 1/T lines as ell as the A H , - XEf values. ~ ~ Zf i e values are small re1:itive to the AIft, value?. Because of the unccrt:iinties of the latter, as well as the boundarl- eonditions of the equation, a high degree of dependence cannot tx placed on values calculated in this manner ( 3 ) . However, the positive or negative direction as \yell as the relative magnitude of the contribution of this term a:: compared to the A H L , vnlucs (T:ilili, 11) is important. I n a n ideal solution, the heat of solution is equal to t,lie heat of vaporization. Quantitative Measurements. Figures 3 and 4 show the types of calibration curves obtained lvith representat'ive chlorinated hydrocarbon conipounds measured both as peak heights and as peak areas in the concentration ranges of our interests. Solutions were prepared b y weighing the required amount of chlorinated hydrocarbon on a n analytical balance and transferring it to a 50-nil. volumetric flask which was already partially filled with a suitable solvent. A second and third solution, respectively onetenth and one-hundredth the concentration of the stock solution, nere prepared and used for the calibration curves. TKth the exception of CH2C12, which covered the range 0 to 25 pmoles, the upper limit of the calibration curves did not, exceed 5 pmoles. Some difficulty was experienced initially in achieving satisfactory calibration curves primarily for two reasons. Care had t o be taken to align the meniscus to obtain equivalent amounts from syringes of lo-, 50-, and 100-p1. sizes, and injection hiid t o be made with repetitive precision to assure evaporation of the ejected liquid but a t the same time to prevent heabing of the needle in the injection port. Careful insertion, rapid injection, and a hold-up
zf
k
I 4 110
9 8
20
2 5
LOG
VAPOR
30
PRESSURE,
74OC
Figure 2. Variation of specific retention volumes of 1 1 chlorinated hydrocarbons with their vapor pressures Compounds a r e numbered according to their increasing boiling points (See Figure 11 Nonpolar columns: A = Apiezon 1; P = paraffin Polar columns: C = Carbowax 4000; T = tritolyl phosphate
Hardy (5) on a dinonylphthlate column (Table 11). Considering the differences in liquid phases, instrumentation, and techniques, the agreement is remarkable. When a liquid phase is a mixture of similar compounds of indefinite molecular weights, such as paraffin, the calculation of a n activity coefficient becomes difficult. However, for a given column, relative activity coefficients may be obtained in as much as the following relationship holds:
I n Table 11, the relative activity coefficients are shown for each of the compounds on the five columns at 74" C. The values were made relative to -& of CHCl&Hl = 1.00, although any of the other compounds may have been used as a reference. Excess Partial Heats of Solution. It has been shown (5, 8, 10, 12) that
where AH, is the molar latent heat of vaporization 1
/
2000, 6' PARAFFIN COLUMN 16.00
97: 59ml/min
In In
I
z
+-
a0 m
U
w U Y W
o
a40
0.80
1.20
160
2.m
2.40
2.00
MICROMOLES OF CHLOROCARBON
,O
Figure 3. heights
Calibration curves based upon peak Figure 4.
040
0.80 I20 160 2.00 MICROMOLES OF CHLOROCARBON
240
280
Calibration curves based upon peak areas VOL. 34, NO. 4, APRIL 1962
479
time of 3 seconds before the needle was extracted gave satisfactory results. Peak height measurements were more difficult to repeat quantitatively but were measured more easily for compounds having low retention times. Peak areas were affected less easily by slight instrumental variations. Careful techniques, including close control of temperature, helium gas flow rate, and injection, and cleanliness of the thermoconductivity cell filaments gave a precision of 1 0 . 0 2 bmole. If necessary, the use of an internal standard would help compensate for slight variations in technique and instrumental conditions. ACKNOWLEDGMENT
Most of the work on this study was
supported by a U. S. Public Health Service Grant No. RG-5575. LITERATURE CITED
(1) Ambrose, D., Keulemans, A. I. M., Purnell, J. H., ANAL. CHEM.30, 1582 (1958). (2) Ambrose, D., zurnell, J. H., “Gas Chromatography, D. E. Desty, ed. p. 369, Academic Press, New York, 19.58. (3) Desty, D. H., Swanton, W. T., J . Phys. Chem. 65, 766 (1961). ( 4 ) Green, S. W., “Vapor Phase Chro-
matography,” D. E. Desty, ed. p. 388, Academic Press, New York, 1957. ( 5 ) Hardy, C. J., J . Chromatog. 2, 490 (1961). (6) Harrison, G. F., “Vapor Phase Chromatography,” D. E. Desty, ed. p. 332, Academic Press, New York, 1957. (7) Haslam, J., Jeffs, -4.R., Analyst 83, 455 (1958). (8) Hoare, M. R., Purnell, J. H., Trans. Faraday SOC.52, 222 (1956).
(9) Jordan, J. E., “Vapor Pressure of Organic Compounds,” Interscience, New York, 1954. (10) .Littlewood, 8.B., Phillips, C. S. G., Price, D. T., J . Chem. Soc. 1955, 1480. (11) Pollard, F. H., Hardy, C. J., Anal. Chim. Acta 16, 135 (1957). (12) Porter, P. E., Deal, C. H., Stross, F. H., J . Am. Chem. Soc. 78, 2999 (1956). (13) Purnell, J. H., Spencer, M. S., h’ature 175, 988 (1955). (14) Rossini, F. D., Wagman, D. D., Evans, W. H., Levine, S., Jaffe, I., “Selected Values of Chemical Thermodynamic Properties,” National Bureau of Standards Circular No. 500, Washington, D. C., 1952. (15) Urone, P., Smith, J. E., Am. Ind. Hyg. Assoc. J . 22,36 (1961). (16) Warren, G. W , Priestley, J. J., Jr., Haskin, J. F., Yarborough, V. A., ANAL. CHEW.31, 1013 (1959). RECEIVED for review November 16, 1961. Accepted January 22, 1962.
Identification of Alcohol Peaks in Gas Chromatography by a Nonaqueous Extraction Technique ROBERT SUFFIS and DONALD E. DEAN Shulton, Inc., Clifton, N. 1. b A technique for the identification of the gas chromatographic peaks due to alcohols has been developed. The method is based on the qualitative separation of the alcohols from other components by a nonaqueous extraction. The peaks removed by the extraction procedure are identified by gas chromatography. Further characterization may be obtained by spectrophotometric methods.
T
of the separated components in gas chromatography has been the subject of considerable study. The most coinnionly utilized techniques involve the isolation of the compounds by solvent trapping or freezing-out. Further analysis is performed by infrared spectrophotometry (1) or mass spectrometry ( 3 ) . Another technique involves the application of functional group identification reactions to the column effluent ( 5 ) . These methods have proved very useful, but they have certain limitations. If very small samples are used, resolution is poor; when destructive detection methods are used, i t may be difficult to use this type of approach. A misture may be analyzed by applying class reactions and then running the gas chromatograms before and after the reaction (4). The disappearance of certain peaks mill identify the functional 480
HE IDESTIFICATIOS
0
ANALYTICAL CHEMISTRY
group of those compounds. This information together \\ ith retention time data nil1 often lead to a definite identification. The identification of alcohols by this technique, known as separation analysis, is the subject of this paper. The method depends on the use of a nonaqueous estraction technique for the qualitative separation of alcohols from other organic compounds. il carbon tetrachloride solution of the misture is extracted with propylene glycol. Alcohols are quite soluble in the propylene glycol layer, whereas aldehydes, ketones, hydrocarbons, and esters are considerably more soluble in carbon tetrachloride. The relative decrease of any peak in the chromatogram of the carbon tetrachloride layer identifies that component as an alcohol. Acids, phenols, and amines are also soluble in propylene glycol. Hon ever, they may be evtracted and identified by aqueous acid or alkali extraction before the nonaqueous extraction. Prior methods for the separation analysis of alcohols involve reaction of these components IT ith benzoyl chloride or 2,4-dinitrobenzoyl chloride ( 2 ) . Our method has the advantage of not introducing any reagents and not converting the alcohols to new compounds. This makes it possible for the alcohols to be separated and identified by infrared or ultraviolet spectrophotometry. The separated layers may be ana-
lyzed directly by ultraviolet spectrophotometry after suitable dilutions. For infrared spectrophotometry, the layers can be extracted with a suitable infrared solvent after water is added to remove the propylene glycol. K h e n equal volumes of propylene glycol and carbon tetrachloride are shaken in a separatory funnel, two layers form. The lower layer is carbon tetrachloride containing 0.1% propylene glycol; the upper layer is propylene glycol with 15% carbon tetrachloride. Ethylene glycol, nitromethane, or acetonitrile may also be used as the polar liquid. Cyclohexane, petroleum ether, or carbon disulfide may be substituted for carbon tetrachloride. APPARATUS
Gas chromatograph, Perkin-Elmer Model 154C Vapor Fractometer a i t h helium as the carrier gas. Infrared spectrophotometry, PerkinElmer Model 21 infrared spectrophotometer. PROCEDURE
Extraction Procedure. A 2-gram sample of the pure compound or miuture is dissolved in 25 ml. of carbon tetrachloride. This solution is placed in a separatory funnel, and 25 ml. of propylene glycol are added. T h e separatory funnel is shaken thoroughly. T h e tn-o layers are separated, and
