10-ml syringe as a weighing pipet. The piston was sealed with silicone oil Prim to taking the mmPle, and the tip of the needle was sealed with a s& cone stopper after taking a sample. The agreement between the two methods for original Grignard reagent as R M ~ X )is excellent, and indicates that decomposition occurred only by hydrolysis. This agreement may be partially the result of using a freshly prepared Grignard reagent. On analysis of 4 year old
phenylmagnesium bromide and tolylmagnesium bromide by a gas chromatographic method (but one using vapor sampling under reflux conditions instead of the one described here) and by acid titration, the acid titration results were found to be about 20% This discrepancy may be the result of some air oxidation of the 4 Year old reagent, which had been stored under nitrogen in a brown bottle closed with a serum stopper.
ACKNOWLEDGMENT
We thank the Burrell Corp. for providing the chromatograph for this research and the Research Corp. for the supplies used in this research. LITERATURE CITED
( 1 ) Clifford, A. F., Olsen, R. R., ANAL. CHEM. 32,544 (1960). (2) Gilman, H., J. Am. Chem. SOC.51, 1576 (1929).
RECEIVED for review February 16, 1961. Accepted April 6, 1961.
Separation and Analysis of Chlorobenzenes in Mixtures by Gas Chromatography HERBERT G. NADEAU and DUDLEY OAKS, Jr. Olin Research Center, Olin Mathieson Chemical Corp., New Haven, Conn.
b A gas chromatographic method for the separation and analysis of a series of increasingly substituted isomeric aromatic compounds is described. The procedure utilizes a temperatureprogrammed chromatograph jo separate all components over a column temperature range of 75" to 260" C. A new partitioning material possessing high selectivity for aromatic compounds and ethers is described and compared to a conventional hightemperature silicone column.
C
MIXTURES of chlorinated benzenes, including some nitro derivatives, have been analyzed for some time by infrared methods (16). It has not always been possible to determine all components prcsent in these mixtures because of the complexity of the infrared spectrum resulting from the numerous similar compounds present and because of a general lack of sensitivity for small concentrations. I n some cases, even qualitative detection is not possible. Gas chromatographic methods of separation and analysis have been reported for various chlorohydrocarbons (IO, 1I ) , including alkyl halides ( I @ , chloronitrobenzenes (Z), and chloroaromatics ( I , 4). These methods demonstrate the extreme utility of gas chromatographic techniques for the separation and analysis of chlorinated organics, but were not as much suited for application to the following series of wide boiling range chlorinated organics, which are in some cases isomeric : benzene, monochlorobenzene (MCB), 0- and p-dichlorobenzene (DCB), 1,2,4 and 1,2,3-trichlorobenzene (TCB), sym- and oictetrachlorobenzene (tetra CB), penta-
RUDE
chlorobenzene (PCB), hexachlorobenzene (HCB), and pentachloronitrobenzene (PCNB) The published methods dealt primarily with separations of relatively low-boiling compounds as compared to the components comprising the mixtures with which this work is concerned (Table I). The various partitioning materials used, unfortunately, were materials which would not stand high temperatures. The wide range in boiling points between isomeric chlorinated benzenes dictated that the gas chromatographic separation would be more effective if it were performed on a high-temperature limit partitioning material and if it were temperature-programmed. Temperature-programmed separations are most
.
Table 1.
applicable where speed and flexibility of operation are requisite in dealing with compounds or groups of compounds possessing a wide spread in boiling points, as in this case. Temperatureprogrammed column heating and some of its applications have been covered adequately in the published literature (3). The method presented effectively utilizes two different high-temperature partitioning agents, either of which is suitable for separation and analysis of these mixtures performed under temperature-programmed conditions. EXPERIMENTAL
Apparatus. F & M linear programmed gas chromatograph, Model 202. A 4-foot column of silicone
Retention Time (Uncorrected) and Response Factors for Compounds on Silicone and High-Boiling Ether Columns
(Response factors are relative t o monochlorobenzene)
Compound Benzene MCB
p-DCB o-DCB 1,2,iTCB 1,2,3-TCB
sym-Tetra CB uic-Tetra CB PCB HCB PCNB 1,4-DNTCB
Boiling Pt.,
O
C.
80.1 132.0 180.4 174.4 213.0 128 to 219 240 to 246 254 275 t o 277 309 (742 mm. Hg) 328
...
Retention Time, Minutes Highboiling Silicone ether 3.0 7.6 13.4 15.0 19.5 20.6 24.1 25.4 31 .O 36.1 37.5 37.8
2.0 6.2 11.0 12.0 16.5 17.5 21.3 22.5 27.0 32.0 36.0
...
Response Factors Highboiling Silicone ether 1 .oo 1.30 1.10 1.30 1.30 1.25 1.42 1.49 1.51 2.70
...
VOL 33, NO. 9, AUGUST 1961
1 .oo 1.23 1.11 1.26 1.20 1.30 1.41 1.44 1.54 2.67
...
1157
I
-0
lyzed by preparing a solution of the mixture in benzene approximating 20y0. A semimicrobalance determines the actual weight per cent. The sample size taken for analysis (0.005 to 0.01 ml.) varies according to the composition of the sample. -4 trail run using the conditions of analysis establishes the optimum sample size. Appropriate attenuation factors are used during the run. Quantitative data are obtained by drawing a base line under each peak and cutting out the respective areas and weighing them on a semimicrobalance. Khen incomplete separation occurs, the areas are determined by dropping a perpendicular to the base line, then cutting out the contained area. The weight of each area is corrected by the appropriate factor. Per cent composition is determined by normalization. If the sample contains large amounts of the higher boiling compounds, it would appear that the high-boiling ether column is more effective, since better separations are effected.
1,2,4 TCB
R
,PCNB
N
I
75.C
pb
125.C Time
lp
minulei
I5
2.0
M O T
25
%0
32
40
Figure 1. Chromatogram of entire series of compounds using 4-foot silicone column
rubber, (F & M Scientific Corp., New Castle, Del.). A 4-foot column of tribenzylsilylbisphenyl ether on Chromosorb 80- t o 90-mesh. Analysis Conditions. Injection port temperature, 300" C.; detector thermoconductivity cell, 100,000ohm; detector voltage, 8 volts; detector block temperature, 250' C.; column temperature, 75' to 260' C.; temperature program, 6.4' C./minute; chart speed, 4 minutes/inch; reference and detector amperage, 10 ma.; sample size, 0.005 t o 0.01 ml.; helium flow, 90 ml./min. Standard Solutions. A series of standard solutions containing the compounds to be analyzed, varying in concentration from 1 t o 5Oy0 of each, was made u p on a weight-weight basis in benzene, employing a semimicrobalance Analytical Columns. The silicone column was prepared directly by introducing into a 4-foot column t h e F & M premix packing. The column was packed uniformly, attached to t h e instrument, and conditioned at 200' C. for several hours. -4 blank program run was made from 0' to 260' C. until the base line was stable. The high-boiling ether column was prepared 30% by weight on Chromosorb W, employing a rotating mixer. The material was uniformly packed in a 3foot column and conditioned similarly to the silicone column. Since this material was of research origin, the column was conditioned for a longer period of time to allow lower boiling mnterials to bleed. Response Factors. The response factors were determined by obtaining chromatograms of standard solutions of the mixtures under the experimental conditions, calculating percentage composition by direct internal normalization, and solving for the factor relating this value to the true value.
+
+
11 58
+
2%
ANALYTICAL CHEMISTRY
D, etc.
DISCUSSION
By direct internal normalization:
area A total area
%A=---
Factor for A =
x
Because most of the compounds concerned within this investigation were solids possessing very high boiling points, the selection of a partitioning material was limited. Of all the materials investigated, the two found most effective were an F & M silicone rubber on Chromosorb material and a research material approximating the composition of 4,4'-bis(tribenzy1)silyl diphenyl ether (TBSDPE). This material is not as yet commercially available, but can be prepared by the following sequence of reactions (5-9, 13, 14).
100
2%
yo .4 detd.
The materials used for the preparation of standard solutions were above 99% purity. No corrections were therefore applied in the above calculations. The response factors reported in Table I are averaged results of multiple determinations a t several concentrations which approximated the concentration levels shown for each component in the synthetic mixtures. The actual spread in concentration level for each component in the mixtures used for the determination of response was about 5%. The method of calculation used is accurate, providing the concentration levels do not change by more than =t15%. Procedure. Samples containing one or more of the compounds are ana-
CBH5CH&1
+ Mg
ether
CsHsCH2MgCl
+ HSiC13
Excess CeHsCHQMgC1
+
BrCsH5-O-CsH~Br 2BuLi 4 (LiCsHs)sO PGHpBr
+
R Sl0,I
75.C
'
Time IO
-
HSi( CH&sH&
P
0
Example : Solution contains 2% A Y% B
+
Total area of chromatogram = area A area B area D, etc.
121.C I" m,nut., I5
200.C 20
a
30
35
Figure 2. Chromatogram of entire series of compounds using 3-foot TBSDPE column
(LiCsHs)zO
+ HSi(CHd2"o)t
ether
benzene
The fraction of the reaction products used for the separation work had the following elemental analysis: .%C Found Theory
83.65 84 10
%H 6.34 6.56
%Si 6 34 7.30
This material possesses a boiling point of 400" C. at less than 0.1-mm. pressure. At slightly elevated temperatures (40" C.), the viscosity approaches that of water, thereby making for convenient column preparation. All components with the exception of H C B from PCNB and 1,CDNTB from PCNB have been separated using the silicone column. The TBSDPE was very good for the separation of all compounds with boiling points above 300" C. Figure 1 illustrates a typical actual chromatogram of the entire series of compounds obtained under the esperimental conditions. Figure 2 represents the same separation performed on the TBSDPE column. Note in the latter case the improved separation of the high-boiling components, particularly between HCB and PCNB; also, the lack of complete separation of oand p-DCB. Table I shows the retention times (uncorrected) and response factors for all compounds on both the silicone and high-boiling ether column. Table I1 shows comparison results obtained on synthetic mistures with both columns. The separation of these multicomponent mixtures has been attempted without temperature programming. At a n intermediate temperature of 150" C., using helium carrier gas and the silicone rubber column, the separations are ineffective for quantitative analysis of all compounds, and much more time is required for separation. Figure 3 represents the best possible separation obtainable under the experimental conditions used. Some exploratory work was done t o determine the over-all selectivity of the TBSDPE column packing. In general, it is extremely effective for the separation of aromatic compounds. It was adequately demonstrated t h a t the material is equally effective for ethers. The separation of glycerine (b.p. 290" C.) from triethylene glycol (b.p. 290" C.) is possible using this column packing. No other column material investigated has worked in this instance. A 1-meter column operating at 200" C. with helium carrier gas shows a cor-
T i m m rninuln
0
11
3p
4s
60
Figure 3. Chromatogram showing separation without temperature programming using 4-foot silicone column a t
150' C.
Table II.
Analysis of Synthetic Mixtures Using Silicone and High-Boiling Ether (TBSDPE) Columns Mixture 50.1 Mixture No. 2 Mixture No. 3
Component Calcd. Founda Foundb Calcd. Founda Calcd. Found* MCB 13.8 13.0 1 2 . 8 ;1 3 . 3 50.7 49.5 7.2 6.8 1 6: 1.6 2.0 1.9 7.8 7.5 p-DCB 1 7 1 3 3 8 3 6 0-DCB 3.81 3.7 5.G 5.9 10.9 11.1 1 0 . 5 ; 10.5 3.1 3.2 14.2 14.9 1,2,4-TCB 101 9 4 l,2;3-TCB 9.6 9.4 10.3; 1 0 . 2 3.8 3.8 6.6 7.0 sym-Tetra CB 9.7 8.9 9.4; 10.0 3.3 3.5 4.5 4.5 uic-Tetra CB 11.8 11.4 12.1:11.8 5.0 5.1 10.1 10.6 23.4 23.4 15.9 16.1 17.0 17.51 1 6 . 6 17.0 PCB 4.8 4.9 4.0 4.1 4.5 4.5; 4 . 7 4.5 HCB 10.7 9.3 6.5 6.9 21.6 17.5; 17.6 18.2 PCNB a Using silicone column. Using high-boiling ether column (TBSDPE).
rected retention time of 1.8 and 4.8 minutes, respectively, for glycerine and triethylene glycol. It would appear from these studies t h a t this column packing is functioning both as a boilingpoint elution column as well as a chemi. cally active material. Inasmuch as the availability of this material is a serious limiting factor, i t would appear that research should be done with similar type available materials. ACKNOWLEDGMENT
The authors thank the Organics Division for the sample of the compound TBSDPE and Samuel Spencer, who performed the glycerine-triethylene glycol separation work. LITERATURE CITED
( 1 ) Beckwith, A. L. J., Waters, W. A,, J. Chem. SOC.1957, 1665. (2) Bombaugh, K. J., ANAL.CHEM.33, 29-32 (1961). (3) Dal Nogare, S., Langlois, W. E., Zbid., 32,767-70 (1960). (4) Freeman, S., Zbid., 32, 1304 (1960).
(5) Gilman, H., J. 079. Chem. 24, 219 (1959). (6) Gilman, H., Catlin, W. E., "Organic Synthesis Collective," Vol. I, p. 471, Wiley, New York, 1948. (7) Gilman, H., Gorsich, R. D., Gaj, B. J., WADC-TR 53-426, Part V, p. 21,
Wright Air Development Command, Dayton, Ohio, 1954. (8) Gilman, H., Shulze, F., J . Am. Chem.
SOC.47,2002 (1925). (9) Gilman, H., Swiss, J., Zbid., 62, 1847 (1940). (10) Green, S.,,W., "Vapor Phase Chromatography, D. H. Desty, ed., p. 388, Academic Press, New York, 1956. ( 1 1 ) Harrison, G. F., Zbid., p. 332. (12) Harrison, G. F., KFight, P., Kelly,
R. P., Heath, M. T., Gas Chromatography," D. H. Desty, ed., p. 216, Academic Press, New York, 1958. (13) Jenkins, J. W., Lavery, N. L., Guenther, P. R., Post, H. W., J . Org. Chem. 13, 862 (1948). (14) Kharasch, M. S., Reinmuth, O., "Grignard Reactions of Nonmetallic Substances," p. 23, Prentice-Hall, 1954. (15) Olin Mathieson Chemical Corp., New Haven, Conn., unpublished data, 1952-61.
RECEIVEDfor review January 25, 1961. Accepted May 29, 1961. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., February 1961.
VOL. 33,
NO. 9,
AUGUST 1961
0
1159
