INTERFACE FOR OPEN-TUBULAR COLUMN SUPERCRITICAL-FLUID CHROMATOGRAPHY ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION MASS-SPECTROMETRY

A new interface for open tubular column supercritical fluid chromatogr aphy (SFC) to atmospheric pressure chemical ionization mass spectromet ry (APCI-MS) is described. The interface was designed to permit transp ort of the supercritical mobile phase into the ionization region of th e mass spectrometer while maintaining its temperature to within +/- 1- degrees-C of the chromatographic oven temperature. Temperature control of the interface-transfer line was achieved using preheated gas strea ms from the chromatographic oven and an active electrical insulation. Ionization was achieved by a point-to-plane corona discharge. The perf ormance of the SFC/MS interface is demonstrated using a number of sele cted analytes showing preserved chromatographic resolution, inertness in the transfer line, and independence of mobile-phase flow rate on io nization, as well as characterization of ionization and fragmentation patterns for compounds from different chemical classes. Test analytes included a polarity mixture over the solubility range of carbon dioxid e. Minimum detectable quantities for anthracene and trilaurin were abo ut 1 ng (S/N = 3) and 10 pg, respectively, while selected ion monitori ng was used. An average retention time reproducibility of 0.24 % RSD w as displayed with an average 2.6 % RSD in relative peak height. Retent ion time correlation between chromatograms obtained with flame ionizat ion detection and mass spectrometric detection is also demonstrated.