Specific detection of primary amines in the effluent of a gas-chromatographic column by on-line measurement of fluorescence.

Compounds with primary amino groups react with o-phthalaldehyde in solution to yield highly fluorescent products. This reaction is now in wide use for detecting amino acids and amines in liquid-chromatography effluents. We report here a method for using o-phthalaldehyde to detect primary amines in the effluent of a gas-liquid-chromatographic column. The effluent gas, nominally 20 mL/min, is delivered to a scrubber consisting of a small-bore, simulated capillary chromatographic column that is simultaneously supplied with 1 mL/min of the reagent solution. The liquid effluent of the scrubber, separated from the gas, is drawn through the flow cell of a fluorometer. Short-chain amines and ammonia were quantitatively scrubbed. The response of the fluorometer was directly proportional to the number of nanomoles injected into the column. Less than a nanomole of amine was detectable. Comparison of results with those from a hydrogen flame-ionization detector showed minimal additional peak broadening or compromise of resolution. These results demonstrate the feasibility of using highly specific, as well as sensitive, liquid-chromatographic detection methods for gas-liquid chromatography.