MIXTURE OF AMMONIA AND HELIUM AS A CARRIER GAS FOR CAPILLARY GAS-CHROMATOGRAPHY

A mixture of ammonia and helium was used as a carrier gas for capillary gas chromatographic analysis of aliphatic amines and dichlorophenols. The peak symmetry for aliphatic amines was drastically improved when the percentage of ammonia was 5-30%. The symmetry continued to improve, although less drastically, between 30-100% ammonia. The capacity factors of the amines decreased with increasing ammonia content up to 100%. 2,5-Dichlorophenol and 2,6-dichlorophenol could not be resolved when helium alone was used as the mobile phase with a column of intermediate polarity (cyanopropylmethylphenylsilicone). Complete separation was, however, achieved by increasing the ammonia content in the carrier gas to 50%. The ratio of the capacity factors (k'(NH3)/k'(He)) for the dichlorophenols increased linearly with increasing ammonia percentage up to 100% on the methylsilicone and cyanopropylmethylphenylsilicone columns.