Capillary Gas Chromatography of Amines with Ammonia as Carrier Gas zyxw baZY JIHG Mohamed Abdel-Rehim Department of Analytical Pharmaceutical Chemistry, Biomedical Centre, University zyxw BA of Uppsala, Box 574, S-751 23 Uppsala, Sweden Moustapha Hassan and Hans Ehrsson* Karolinska Pharmacy, Box 60024, S-104 01 Stockholm, Sweden Key Words: Capillary gas chromatography Ammonia Aliphatic amines Aromatic amines Summarv The use of ammonia as a carrier gas for the chromatography of aliphatic and aromatic amines has been investigated. As compared to nitrogen, ammonia gave drastically improved peak symmetry and lower capacity factors zyxwvut GFEDCB (k') for primary and secondary amines on polar (polyethylene glycol) and medium polar (methylphenylcyanopropylsilicone) stationary phases.The effect of ammonia was more pronounced at zyxwvut A low column temperatures. Considerably better detection limits of primary and secondary amines were obtained with ammonia as carrier gas than with nitrogen. No detrimental effects of using ammo- nia were observed on the gas chromatograph or on the columns over a period of about one year. 1 Introduction zyxwvuts MLKJIHG Despite great progress in gas chromatography during the last decade some difficulties limit the use of the technique, e.g. adsorption of polar compounds like amines, carboxylic acids, and phenols in the chromatographic system. Non-inert mobile phases such as ammonia, carbon dioxide, water, and formic acid have been recommended for the analysis of polar compounds [ 1-51 due steel tubes. The original flow regulator for the nitrog replaced by a Brooks 8606 pressure regulator (0-60 psi) an check relief valve (1 psi) was mounted after the pressure regul to prevent back flow of ammonia through the nitrogen tub inlet was put up for ammonia with a pressure regulator (B 8606)'and the liner after the pressure regulator was con with the nitrogen liner through a tee coupling after the ch valve. The split outlet was drawn and mounted outsid instrument and the split ratio was regulated through a valve (Swagelok). The detector was the original flame ioni detector and the make up gas (nitrogen) was led from the second injector port and to the FID through a tee coupling after th column. The flow of make up gas was regulated by a flow regulator to 30 ml/min. 2.2 Carrier Gases and Measurement of Flow Rate Nitrogen, air, and hydrogen were of high purity grade. Am had a purity of 99.95 %. All gases were purchased from AGA Ga (Sweden). The ammonia was dried by connecting a glass col (60 cm) packed with zyxw CBA KOH to the ammonia cylinder after th primary pressure regulator. to their deactivating effect on the solid surfaces. Amines consti- tute an important group of compounds due to their extensive use in the pharmaceutical industry and in the preparation of many chemicals. The analysis of amines by gas chromatography has in most cases been carried out after derivatization 161. The aim of the present study was to study the effect of ammonia as The nitrogen flow rate was measured using a capillary colum bubble meter. The ammonia flow rate was measured using a Flow-Check flow meter (Dwyer Instrument, Inc., USA), after replacing all copper tubes with stainless steel tubes. 2.3 Columns and Operating Temperatures a mobile phase on the capacity factor, peak symmetry, and detection limit of aliphatic and aromatic amines. The analysis was performed on three columns covering a wide range of polarity using ammonia and nitrogen as carrier gases. 1) Supelcowax 10, Supelco (polyethylene glycol): 2) CP-Sil-19CB, Chrompack, (methylphenylcyanopropylsili- length: 10 m, i.d.: 0.32 mm, film thickness: 0.50 pm. cone): 2 Experimental 2.1 Apparatus length: 10 m, i.d.: 0.32 mm, film thickness: 0.21 pm. 3) HP, Hewlett-Packar d, (met hylsilicone) : length: 25 m, i.d.: 0.32 mm, film thickness: 0.52 pm. All the used columns were crosslinked. The gas chromatographic analysis was performed using a Hewlett Packard instrument (model 5710 A). The original injector was substituted by an injector splitter (model A) obtained from Chrompack. The copper tubes from the carrier gas inlet to the injector and to the split flow regulator were replaced by stainless The polyethylene glycol column was operated at 90 "C for the aliphatic and 120 "C for the aromatic amines. The methylpheny cyanopropylsilicone and methylsilicone columns were ope at 90 "C for both aliphatic and aromatic amines. The detector an injector temperatures were 250 "C. 252 Journal of High Resolution Chromatography Q 1990 Dr Alfred Huethig Publishers