Application of a laser intracavity absorption detector to gas chromatography of trace organic pollutants in water

A helium-neon (HeNe) laser operating simultaneously at 3.39 micrometers (infrared) and 0.63 micrometer (visible) were used as a selective detector for hydrocarbons in the effluent of a gas chromatography. The infrared and visible laser transitions originate at the same energy level and are competitive. In practice, the detector's selectivity for hydrocarbons is modified by various substituents. The detector responds to aliphatic and aromatic hydrocarbons with aliphatic side chains, except for those substituted with halogens. The HeNe laser intracavity absorption detector may be used without prior separation in some cases (e.g., methane in coal mines). This detector operates with nitrogen carrier gas without sacrifice of sensitivity and should be useful for monitoring organic pollutants since it does not respond to water or carbon dioxide. Also, it should be possible to manufacture this detector at competitive prices.