Repetitive liquid injection system for inverse gas chromatography

Abstract

A hybrid injection system composed of a closed-loop vaporization chamber with a gas sampling valve is described. The system allows liquid injection into the vaporization loop with subsequent multiple injections of the vaporized solute(s) via the gas sampling valve (GSV). Very small amounts of probe solutes can be injected without a dilution solvent, and the vaporization loop acts as a “retention gap” for capillary columns. The use of a pneumatically controlled valve injector provides very accurate and reproducible injection volumes at precise time intervals. Combination of precisely timed injections with temperature programming of the column oven produces continuous chromatograms and retention data at controlled temperature increments. The proposed injection system eliminates the need for split injectors; it is cleaner than normal in-line injectors because nonvolatile samples cannot reach the column; and the instrumentation is easily automated. The major disadvantages are the restriction that the samples must be volatile at temperatures lower than the upper temperature limit of the valve rotor; the GSV is susceptible to both contamination and mechanical failure; the sample can be exposed to metal components of the valve; and initial distribution of the sample throughout the closed-loop vaporization chamber may be slow.