Gas-Liquid Chromatographic Separation of the Ten Geometric Isomers of Chloromethylaniline Using Ucon Oil as Stationary Phase on a Textured Glass Bead Support Edward Townley, Isidoro Perez, and Peter Kabasakalian Research and Development Division, Schering Corporation, Bloomfield, N . J . 07003 THE GEOMETRICAL ISOMERIC purity determination of chloromethylanilines by gas-liquid chromatography (GLC) has not been reported previously in the literature. The GLC separation of the 10 possible isomers is difficult because of similar boiling points and polarities. GLC resolution of the related disubstituted benzenes have been reported : ortho-, meta-, and para-chloroanilines (I)and methylanilines (2). However, these separations have been difficult and involved long retention times (ca. 50 min). The most successful liquid phases for these disubstituted benzenes have been highly polar and selective materials such as sodium dodecylbenzenesulfonate (I),the polyglycol-type liquid phases [glycerol (3) and diglycerol (3)],and several Ucon oils ( 2 ) . Ucon oils ( 4 ) also have been used successfully for the separation of four of the six possible geometric isomers of the trisubstituted benzenes, dichloro- and dimethylaniline. Our studies showed that glycerol and diglycerol were too volatile for the chloromethylaniline separations. Sodium dodecylbenzenesulfonate was even less satisfactory. Other thermally-stable materials such as SE-30, OV-17, or neopentylglycol succinate (NPGS) were not suitable for these separations. Columns prepared with 1 Ucon oil (50-HB2000 or 50-HB-5100) on 6 x potassium hydroxide coated (I) commercial diatomaceous earth supports (Gas-Chrom Q or Diatoport S) gave only partial separations. Greater column efficiencies than are available normally (300-400 theoretical plates/ft) were required. Therefore we tried Corning textured glass beads; Corning claims ( 5 ) efficiencies of 600-1200 theoretical plates/ft of column depending on the mesh size. We have separated successfully the geometrical isomers of chloroaniline, methylaniline, and chloromethylaniline.
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EXPERIMENTAL
Apparatus. A Model 400 (F & M Scientific Corp.) gas chromatograph was used with a hydrogen flame ionization detector. The recorder had a 1 mV full scale range with a chart speed of 0.5 inches/min. Isothermal column temperature was maintained at 120 “C for the chloroanilines and methylanilines and 150 “C for the chloromethylanilines. The injection port and the detector oven were maintained at 200 “C with a helium flow of 50 ml per minute through the column. The boiling points were performed in the “standard cell” of the Du Pont 900 Differential Thermal Analyzer. Reagents. The isomeric chloroanilines, methylanilines, and nine of the chloromethylanilines were purchased from readily-available commercial sources. The tenth isomer, (1) K. J. Bombaugh, ANAL.CHEM., 37,72 (1965). (2) J. S.Parsons and J. C. Morath, ibid.,36, 237 (1964). (3) M. Anwar, C. Hanson, and A. N. Patel, J . Chromatogr., 34, 529 (1968).
(4) H. G. Henkel, J. Gas Chromatogr., 3, 320 (1965). (5) Corning Glass Works, Corning, N. Y . , Corning Chroma-
tography Products, Product Information Data Sheet 102.
3-chloro-5-methylaniline, was synthesized (6). Five microliters of a heptane solution containing 100 pg/ml of the isomeric compounds was injected into the gas chromatograph, Column Preparation. DMCS-treated Corning textured glass beads (GLC-110, 80-100 mesh) were coated by the Corning procedure (5): 100 ml 0.05 % alcoholic potassium hydroxide plus 20 g of glass beads were poured into a 250-ml filtering flask. The flask was stoppered and swirled occasionally while vacuum was applied for 5 min. The slurry was vacuum filtered through a medium porosity sintered glass funnel until the excess solution was barely removed. The “wet” glass beads were transferred into a shallow dish inch, allowed to dry slowly at room temto a depth of perature, and stirred occasionally. These potassium hydroxide treated beads were coated with 0.4 gram Ucon oil (50-HB-5100) dissolved in 100 ml of chloroform, by the same procedure. Glass U columns inch o.d., 6- and 10-ft) were completely filled with the coated glass beads without tapping. Then the columns were packed by tapping a glass rod, held between the two arms of the column, alternately from side to side simultaneously moving from the bottom towards the top. These columns exhibited 800 theoretical plates/ft of column for 3-methyl-2-chloroaniline. RESULTS AND DISCUSSION
We separated the three geometrical isomers of chloroaniline (Figure 1) and methylaniline (Figure 2) with the 6-ft Ucon oil on textured glass bead column in shorter time (5-13 min) than reported previously (I, 2). (6) D. Browne and G . Dyson, J. Chem. SOC.,1931,3285. ANALYTICAL CHEMISTRY, VOL. 42, NO. 8, JULY 1970
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Figure 3. Separation of geometric isomers of chloromethylaniline
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M / N UTES Figure 2. Separation of geometric isomers of methylaniline Eight of the ten isomeric chloromethylanilines were completely resolved (Figure 3) on the 10-ft column. 2-Chloro-3methylaniline and 2-chloro-5-methylaniline were only partially resolved (Figure 3). The increasing order of retention times of the chloroaniline and methylaniline isomers was ortho, para, and meta. This sequence corresponds approximately to their boiling point order. However, in the case of the chloromethylanilines, this does not hold as evidenced by the boiling points (Figure 3) determined with the DTA apparatus. Here there are many inversions in the sequence, indicating that polarity factors are influencing the sequence. The retention times fall into two classes (short and long) just as in the chloroaniline case. All four short retention-time isomers (boiling points about 230 "C) have the chlorine ortho to the amino group. The
sequence within this group appears to depend on the relative position of the methyl to the amino substituent: ortho, para, and meta as in the case of the methylanilines. The two compounds which were most difficult to resolve both have the methyl substituent meta to the amino group. The methyl group ortho to the chlorine has the smaller retention time of these two. With the long retention-time isomers (boiling points about 245 "C) the methyl group exhibits the ortho, para, and meta relationship to the amino group while the chlorine has the secondary effect. The first isomer has all the substituents adjacent to each other, similar to the first isomer in the other series, whereas the distinctly last member has all substituents meta to each other. Now we can, therefore, routinely analyze the isomeric purity of these trisubstituted benzene compounds. Because of their high efficiency and selectivity, these columns are recommended for a variety of similar difficult separations. RECEIVED for review March 9,1970.
Accepted April 21,1970
Determination of Carbon in High Purity Metals by Photon Activation Analysis G . J. Lutz and L. W. Masters Analytical Chemistry Division, National Bureau of Standards, Washington, D. C. 20234 NONMETALLIC IMPURITIES, such as carbon, nitrogen, and oxygen can have marked effects on the metallurgical, electrical, and electronic properties of metals. The current state of materials science requires the development of very sensitive methods for their determination. Traditional methods of carbon analysis involve the burning of the sample in a stream of oxygen, followed by trapping 948
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the carbon dioxide from the gas stream, either in liquid air or an aqueous hydroxide solution and then determining the carbon dioxide by manometry or conductance measurements. This determination at and below the ppm level is complicated by oxygen and equipment blanks, which may yield an analytical signal larger than that due to the carbon to be determined and may not be susceptible to accurate evaluation.
