REPETITIVE LIQUID INJECTION SYSTEM FOR INVERSE GAS-CHROMATOGRAPHY

A hybrid injection system composed of a closed-loop vaporization chamb er with a gas sampling valve is described. The system allows liquid in jection into the vaporization loop with subsequent multiple injections of the vaporized solute(s) via the gas sampling valve (GSV). Very sma ll 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 inte rvals. Combination of precisely timed injections with temperature prog ramming of the column oven produces continuous chromatograms and reten tion data at controlled temperature increments. The proposed injection system eliminates the need for split injectors; it is cleaner than no rmal in-line injectors because nonvolatile samples cannot reach the co lumn; and the instrumentation is easily automated. The major disadvant ages are the restriction that the samples must be volatile at temperat ures lower than the upper temperature limit of the valve rotor; the GS V is susceptible to both contamination and mechanical failure; the sam ple can be exposed to metal components of the valve; and initial distr ibution of the sample throughout the closed-loop vaporization chamber may be slow.