PROBE INTERFACE FOR SUPERCRITICAL FLUID CHROMATOGRAPHY FOURIER-TRANSFORM MASS-SPECTROMETRY

A versatile probe-mounted interface for supercritical fluid chromatography/Fourier transform mass spectrometry has been designed, constructed, and evaluated. The interface is fully contained within a 40 in. long stainless steel tube and provides for accurate transfer line temperature control and separate control of a noninductively wound probe tip heater. The tip can be continuously held at temperatures above 600 degrees-C. Separate current and thermocouple vacuum feedthroughs allow for convenient tip removal and SFC pressure/flow restrictor replacement. The tip heater utilizes a copper disk to protect the fragile restrictor tip and to serve as an anode for the electron beam source. The probe is easily inserted through a standard probe lock without disruption of the high-vacuum system. Functional characteristics of the new SFC/FTMS probe interface are demonstrated by analyses of cholesterol and a polyaromatic hydrocarbon mixture. Cholesterol shows minimal dehydration, as evidenced by the appearance of its molecular ion as the base peak in its mass spectrum. Detection limits of approximately 100 pg are demonstrated for aromatic hydrocarbons.