Direct Supersonic Expansions of Supercritical Fluids for Analysis of Polycyclic Aromatic Hydrocarbons

Abstract

Significant line-narrowing has been observed in the laser-induced fluorescence spectra of naphthalene and perylene in direct supersonic expansions of simple supercritical carriers such as CO₂, N₂O, and even SF₆, under conditions which minimize aerosol and cluster formation. Clusters form readily in expansions of CO₂ and N₂O unless nozzle temperatures exceed about 200°C. Results with more complex carriers, such as n-pentane, are much poorer. Selective detection of perylene at a limit of 2 ng (S/N = 3) in a mixture of ten polycyclic aromatic hydrocarbons and in a coal tar extract has been achieved with a capillary introduction system. Challenges with coupling supersonic jet detection to capillary supercritical fluid chromatography lie with the nozzle.