The mass spectrometer revealed the presence of small amounts (0.06 to 0.1 mole %) of C1802. The equivalent of this as c160180 was accommodated in the final computation. With a rich sample of H2180(55 atomic % the C 1 8 0 ~ amounted to 2.8 mole % of the total Con. The C180z evidently arises from the exchange of C16O17O with unreacted Hz180.
ACKNOWLEDGMENT
The mass spectrometric analyses were carried out by Maurice Frech. RECEIVED for review February 27, 1968. Accepted April 25, 1968.
Separation of Chlorostyrenes and Ethylbenzene/Xylenes Charles F. Raley and J a m e s W. Kaufman Physical Research Laboratory, The Dow Chemical Co., Midland, Mich. ORGANO-CLAYS have been previously discussed as chromatographic supports for the separation of various aromatics. The separation of ethylbenzene and the xylenes has received particular attention. Columns of Bentone-34 modified with diisodecyl phthalate ( I ) , silicone oil (2, 3), tricresyl phosphate, and dinonyl phthalate ( 2 ) have been described. In the present work, the separation of the isomeric monochlorostyrenes and ethylbenzene/xylenes using a column of Bentone-34 packing modified with bis-(phenoxyphenyl) ether (4P3E) was compared with the separations obtained using these other packings. The best separation of the xylenes was obtained with the Bentcne-34/dinonyl phthalate column. The separation of the six isomeric chlorostyrenes was best on the 4P3E-modified column.
Apparatus. The apparatus, using on-column injection, was constructed in this laboratory. It employed a Podbielniak Type 9981 thermal conductivity detector with Gow-Mac W filaments, and a Sargent Model S-72180-35 1 mV recorder. The columns were 12-foot X 3/16-in~h 0.d. stainless steel tubing (operating conditions shown in Table I) packed with the following: 10 pph Bentone-34; 5 % Bentone-34 and 5 % diisodecyl phthalate (DDP); 10 pph Bentone-34 and 10 pph silicone oil (DC-550); 10 pph Bentone-34 and 10 pph tricresyl phosphate (TCP); 10 pph Bentone-34 and 10 pph dinonyl phthalate (DNP). The columns of Bentone-34 and Bentone34/4P3E used 70-80 mesh Anakrom AS support; the last three were on 60-100 mesh Chromosorb W. The proportions of ingredients and types of support were chosen to duplicate those previously used. Column Preparation. The column was prepared in the usual fashion, by slurrying the support and liquid phase in benzene, and flashing off the volatiles. For example, to a ( 1 ) S. F. Spencer, ANAL.CHEM., 35, 592 (1963). (2) J. V. Mortirner and P. L. Gent, ibid.,36,754 (1964). (3) E. W. Cieplinski, ibid., 37, 1160 (1965).
Table I. Operating Conditions Chlorostyrenes Alkylbenzenes 150 170 250 50 0.3
v)
z 0
n v)
W K
K
EXPERIMENTAL
Column temp, "C Injection port temp, "C Detector temp, "C Helium flow, cc/min Sample size, p1
W
100 170 250 50 0.3
W 0
K
0 0
----hhL
L!
n
W
K
c
D.E
F
0 pph BENTONE-34 /IOpph DC-550
n
E
Adu
Lj
&C E F
0.G
3 pph BENTONE-34/lOpph TCP
O(AIR)
5
IO
15
20
25
TIME (MIN.)
Figure 1. Separation of chlorostyrenes solution of 1.25 grams of 4P3E (The Dow Chemical Co.) in approximately 100 ml of benzene was added 2.5 grams of Bentone-34 (National Lead Co.). After the suspension was stirred for 1 hour, 25 grams of Anakrom AS was added and thoroughly stirred. The benzene was flashed off using a rotating baffled flask attached to a Rinco Model VE-1000-B evaporator. The devolatilization was carried to 100 "C at 0.8 mm. A straight length of stainless steel tubing, 12 feet x 3/16 inch 0.d. was filled with this packing, plugged with glass wool and wound into a coil. The columns were conditioned at 150 "C for 12 hours before use. The packing of Bentone-34 and D D P was obtained from F&M Scientific Corp. under catalog No. LP14. DC-550 is the trademark of Dow Corning Corp. for a silicone oil containVOL. 40, NO. 8 , JULY 1968
0
1371
I
A.
TOLUENE
8. E T H Y L B E N Z E N E
IOpph BENTONE-34
w
TOLUENE ETHYL-
C.
para-XYLENE
D.
rneto-XYLENE
E.
ortho-XYLENE
v)
z 0
a
BENZENE
v)
W
poro-XYLENE mela-XYLENE
a
a w
n
ortho-XY LENE
K
s
5 % BENTONE-34/5%DDP
W
a A. T O L U E N E
E. ortho-CI
STYRENE
E. para-CI S T Y R E N E
F. C. meta-CI S T Y R E N E IOpph BENTONE-34/5pph 4 P 3 E
.. OtAIR)
5
10
15
0 (AIR)
5
TIME (MIN.)
10
TIME (MIN.)
x
DISCUSSION The unmodified Bentone-34 column gave good separation of para-, meta-, a- and cis-0-chlorostyrene but did not separate trans+ from ortho-. The peaks were quite broad. The column of Bentone-34 and DDP separated only cis- and trans/3- (themselves poorly resolved) from the other components. The column of Bentone-34 and 4P3E separated all six components sharply. The DC-550-modified column gave results similar to unmodified Bentone-34, although with sharper peaks and less elution time. The resolution with TCP modifier was poor. The results with D N P were next best to 4P3E, showing somewhat poorer separation and peak sharpness and a longer elution time. It is interesting that with all columns, Peaks B, C , E, F, and G elute in the same order; only the relative position of Peak D (trans-0-chlorostyrene) is shifted. These results are shown in Figure 1. Incidentally, a 12-foot X 3 / ~ 6 inch column of 10 % 4P3E on 60-80 mesh Anakrom AS separated only cis-0- and trans+- from the other chlorostyrenes, which were not themselves resolved. A comparison of the resolution of ethylbenzene/xylenes on the same six columns was then made. The unmodified column of Bentone separated the ortho-, meta-mixture from the para-xylenelethylbenzene (slight resolution). Bentone/DDP did not adequately resolve the meta, para isomers. The peaks were much sharper than with Bentone-34 alone. With the column of Bentone-34 and 4P3E, the resolution of ethylbenzene and para-xylene was about the same as with Bentone-34 and DDP but meta- and para-xylene were sharply separated. Undoubtedly the resolution could be further optimized. DC-550 gave almost the same separation as 4P3E although with a longer elution time. The performance of TCP was poor. The DNP-modified column gave the best separation, although with broader peaks and longer retention times than 4P3E. In every case, the various components eluted in the same order. The curves are shown in Figure 2. 1372
ANALYTICAL CHEMISTRY
G. cis-beta-CI STYRENE
D. trans- beta-C I S T Y R E N E I
1
I
I1
0 (AIR)
5
10
15
T I M E (MIN.)
Figure 2. Separation of ethylbenzene/xylenes ing 50 mole methylphenylsilyl and 50 mole % dimethylsilylgroups. The TCP was a technical grade of tritolyl phosphate obtained from Matheson, Coleman & Bell. A chromatographic grade of dinonyl phthalate was obtained from Analabs, Inc., Hamden, Conn., under catalog No. GP51.
alpha-CI S T Y R E N E
Figure 3. Separations by octadecylarnine on Anakrom AS It thus appears that a column packing of Bentone-34 and 4P3E offers significant advantages in the resolution of the chlorostyrenes and, to a lesser extent, of ethylbenzene/xylene mixtures. It seems quite possible that the selectivity of Bentone-34 is due to its stable, highly adsorptive, oleophilic surface coating, the solubility parameter ( 4 ) of which may be rather precisely modified by the addition of stationary phases of varying degrees of polarity. Its major advantage over a support coated with an oleophilic stationary phase, e.g., silica coated with octadecylamine, may well be the firmness of attachment-ionic us. coordinate bonding-preventing loss of the coating by volatilization. For example, a 12-foot X 3/16-in~h column containing 70-80 mesh Anakrom AS coated with 3.6 pph octadecylamine (equal in C to 10 pph Bentone-34) at 100 “C separated the alkylbenzenes in about the same fashion as 5 Bentone-34/5 DDP on Anakrom AS and somewhat better than 10 pph Bentone-34 on Anakrom AS, as shown in Figure 3. The gas rate was 25 cc/minute. The order of elution was the same. The separation of the chlorostyrene mixture by the same column (100 “C, 50 cc/rninute gas rate) was rather inefficient but still better than DDP- and TCP-modified Bentone. The order of elution was unique, the meta-paru pair eluting before the ortho-a. This column was thermally unstable, the octadecylamine being slowly driven off, resulting in ever-decreasing elution times.
x
x
ACKNOWLEDGMENT The authors thank James R. Runyon and Donald E. Zahm who constructed and made available this apparatus.
RECEIVED for review January 26, 1968. Accepted April 29, 1968. (4) J. H. Hildebrand and R. L. Scott, “The Solubility of NonElectrolytes,” Third Ed., Reinhold, New York, N. Y., 1949, p 129.
