Concentration of volatile organic compounds from solvents by sustained chromatographic evaporation

Abstract

AbstractA system for quantitative concentration of volatile organic trace compounds present in organic solvents is described. Evaporation of the solvent is carried out inside a glass capillary tube by the action of a carrier gas, and large volumes can be reduced by a repeated sample injection and a cyclic flow reversal. Best recovery is obtained when a barrier of pure solvent is maintained ahead of the sample during concentration. Four rotary valves are employed for sample and solvent injection and direction of the gas flow. In principle, indefinite sample volumes can be handled, the limit being set by system contaminants.The process was evaluated both off‐line and on‐line to a gas chromatograph. Concentration of compounds like methylcyclopentane, hexane, and cyclohexane present in pentane in the low nanogram range and subsequent on‐line transfer to a gas chromatograph could be performed with a quantitative recovery. The technique was applied to analysis of trace volatiles in drinking water. Detection limits were estimated to be approximately 0.02 ng/L for normal hydrocarbons (FID detection) when concentration of a pentane extract from a one litre water sample was carried out.