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Gas - Liquid Chromatographic Separation of Chloroaniline and Toluidine Isomers on Heteroaromatic Stationary Phases

Aoi Ono" Chemical Laboratory, Takada Branch, Faculty of Education, Niigata University, Nishishiro-cho, Joetsu-shi, 943 Japan

Keywords : Gas - liquid chromatography ; separation of chloroaniline isomers ; separation of toluidine isomers ; heteroaromatic stationary phases

Although chloroaniline and toluidine isomers are important materials in the chemical industry, their complete gas - liquid chromatographic resolution has seldom been accomplished. Various liquid stationary phases have been investigated for this purpose : James1 used paraffin, benzyldiphenyl and Lubrol MO ; Fitzgerald2 used silicone E-51, glycerol and hexakis( cyanoethy1)melamine ; Funaoka et aZ.8 used &glycerol and sodium dodecylbenzene sulphonate ; Henke14 used Ucon 50HB 2009 ; Bombaugh6 used Siponate PS-10, polyethylene glycol 20M and silicone oil; and Snegova et aZ.6 used a mixed phase of PFMS-4 and fluoro- silicone oil 169. However, there have been few systematic studies of the separations and for this reason, this work was undertaken.

This paper reports the results obtained by using (mainly) heteroaromatic compounds as stationary phases for the separation of chloroaniline and toluidine isomers.

Experimental Stationary Phases

Nicotinic acid, 1H-benzotriazole, nicotinamide, N-ethylurea, benzimidazole, benzo- guanamine, carbazole, #-aminobenzoic acid, hydantoin, imidazole, melamine and succinimide, obtained as guaranteed grade materials from Nakarai Chemical Co. (Kyoto, Japan), were used after purification.

* Present address : Department of Chemistry, Faculty of Education, Niigata University, Niigata, 950-21 Japan.

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August, 1981 SHORT PAPERS 907 Samples

The o-, m- and $-chloroaniline isomers and the o-, m- and $-toluidine isomers were of guaranteed grade obtained from Tokyo Kasei Kogyo (Tokyo, Japan), and were used after purification.

Apparatus

detector was used. A Shimadzu, Model GC-5A, gas - liquid chromatograph equipped with a flame-ionisation

Chromatographic Procedure The separation column was a 2.25m x 3 mm i.d. stainless-steel U-tube packed with a

60-80-mesh acid-washed C,,firebrick support that was coated with 20% m/m of the stationary phase. Nitrogen was used as the carrier gas a t a flow-rate of 25 rnl min-l. The two sample solutions in tetrahydrofuran contained almost equal amounts (by mass) of constituents. The sample size was 0.5-1.0 pl.

The column and injector temperatures were 140 and 270 "C, respectively.

Results and Discussion In the resolution of aniline derivatives by gas - liquid chromatography, the supports

utilised are usually treated with several per cent. of alkali, in order to avoid the adsorption of the amine on to the acidic parts of the support.' However, for this study the supports were not treated with an alkali, as, for most of the stationary phases being investigated the gas - liquid chromatographic procedure appeared to be unhindered.

Separation of Chloroaniline Isomers As shown in Table I, lH-benzotriazole, benzimidazole, benzoguanamine, carbazole,

hydantoin, imidazole, melamine, nicotinic acid and nicotinamide, which are nitrogen- containing heteroaromatic compounds (triazine, pyrrole or pyridine derivatives), resolved chloroaniline isomers effectively. N-Ethylurea, 6-aminobenzoic acid and succinimide (aro- matic amine or aliphatic amine or amide) also resolved these isomers effectively. However, only N-ethylurea, benzimidazole, benzoguanamine, carbazole, melamine and succinimide gave base-line separation of the isomers and it was difficult to obtain complete separations.

TABLE I RELATIVE RETENTIONS OF CHLOROANILINES ON STATIONARY PHASES EXAMINED

Relative retention is based on adjusted retention time.

Stationary phase Nicotinic acid . . IH-Benzotriazole . . Nicotinamide . . N-Ethylurea . . Benzimidazole . . Benzoguanamine . . Carbazole . . . . p-Aminobenzoic acid

Imidazole . . . . Melamine . . Succinimide . .

H ydantoin . .

Relative retention r \ o-Chloro- m-Chloro- p-Chloro- aniline aniline aniline

A

. . 1.00

. . 1.00

. . 1.00

. . 1.00

. . 1.00

. . 1.00

. . 1.00

. . 1.00

. . 1.00

. . 1.00

. . 1.00

. . 1.00

2.15 2.80 2.56 2.67 2.42 2.29 2.35 2.26 2.11 2.86 2.18 2.89

2.85 4.30 3.11 3.56 3.21 2.71 3.12 2.49 2.58 3.14 2.59 5.55

Retention time of o-chloroaniline/min

1.30 1 .oo 0.90 0.90 2.40 1.40 3.40 3.50 1.90 0.70 2.20 1.80

Separation of Toluidine Isomers As shown in Table 11, 1H-benztriazole, benzimidazole, benzoguanamine, carbazole,

hydantoin, imidazole, melamine, nicotinic acid, nicotinamide and N-ethylurea separated the toluidine isomers effectively but $-aminobenzoic acid could not separate m-toluidine

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from p-toluidine. Further, benzimidazole, carbazole and melamine gave almost complete base-line separation of these isomers.

TABLE I1 RELATIVE RETENTIONS OF TOLUIDINES ON STATIONARY PHASES EXAMINED

Relative retention is based on adjusted retention time.

Relative retention

Stationary phase Nicotinic acid . . 1H-Benzotriazole . . Nicotinamide . . N-Ethylurea . . Benzimidazole . . Benzoguanamine . . Carbazole . . .. P-Aminobenzoic acid

Imidazole . . . . Melamine . . . . Succinimide . .

H ydantoin ..

o-Toluidine . . 1.00 . . 1.00 . . 1.00 . . 1.00 . . 1.00 . . 1.00 . . 1.00 . . 1.00 . . 1.00 . . 1.00 . . 1.00 . . 1.00

7

m-Toluidine P-Toluidine 1.38 1.66 1.78 2.83 1.50 1.71 1.24 1.53 1.31 1.51 1.43 1.57 1.32 1.50 1.43 1.43 1.29 1.50 1.41 1.76 2.18 2.59 1.55 1.69

Retention time o-tohidinelmin

2.10 2.30 1.40 1.70 4.90 1.40 5.60 3.70 2.40 1.70 2.55 3.10

Conclusion Although chloroaniline and toluidine isomers are aniline derivatives, their separation

behaviour on the stationary phases examined here are different. Benzimidazole, carbazole and melamine showed effective base-line separation for both series of isomers but N-ethyl- urea, benzoguanamine and succinimide gave effective base-line separation for chloroaniline isomers, but not for toluidine isomers.

Finally, the separation of the two series of isomers on heteroaromatic or aliphatic basic compounds could be performed effectively on supports that had not been treated with alkali.

References 1. 2. 3. 4. 5. 6. 7.

James, A. T., Anal. Chem., 1956, 28, 1564. Fitzgerald, J. S., Azlst. .J. Appl . Sci., 1961, 12, 51. Funaoka, W., Kojima, T., and Igaki, H., Anal. Chem., 1964, 36, 2214. Henkel, €3. G., J. Gas Chvornatogr., 1965, 3, 320. Bombaugh, K. J., Anal. Chem., 1965, 37, 72. Snegova, A. D., Motsarev, G. V., and Treger, Yu. A., Zh. Anal. Khim., 1970, 25, 1423. Kotake, M., “Jikken Kagaku Koza, Zoku, Volume 9, Gas Chromatography,” Maruzen, Tokyo, 1972,

Received November 24th. 1980 Accepted March loth, 1981

p. 376.

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