Temperature setting, splitless inlet

Glass Liners Ferrules and Fittings Setting the Inlet Temperature Setting the Flows and Split Ratio Discrimination and Linearity of Splitting SPLITLESS INLET... 

Splitless injection is used when the sample is dilute and cannot be introduced into the GC system with stream splitting. In practice, the column temperature is set 10° to 30°C below the boiling point of the solvent at the time of injection. When sample is introduced into the injector inlet, vaporized solvent together with the FAME condense at the beginning of the column along with the carrier gas flow. The condensed solvent plus the stationary phase of the column forms a diluted stationary phase that traps the FAME in it. After the initial sample introduction period, the column temperature is raised to normal operating conditions, and chromatographic separation starts from there. 

GC-MS was performed on a Hewlett-Packard 6890 GC wifli 7683 autosampler and 5973 mass-selective detector (Agilent Technologies, Palo Alto, CA). Electron impact (El) MS was obtained at 70 eV. A split / splidess injector was used in splitless mode with a purge flow to split at 2.0 min after injection. Chromatograms were run at a constant flow of 0.5 mL /min of He gas. TTie inlet tenq>erature was set at 250 C. An HP-5MS (5% diphenyl-95% dimethylsiloxane) capillary column (30 m x 0.25 mm, 0.25 pm < ) was used with temperature programming from 60 C (1 min hold) to 300 C at 10 C/min witii a al 10 min hold. Solvent samples (1 pL) were injected by the autosampler. SPME sanqrles were manually injected by insertion of the fiber into the mass spectrometer inlet until after the purge flow to split occurred. Mass spectra were recorded from m/z 40 to m/z 550. 

The transfer can only be partial for concentrated extracts (split mode), or a total transfer of the sample into the column for trace analysis is performed (splitless mode). Both injection methods require a different parameter setting, choice of inlet liners and oven program start temperature to achieve the optimum performance. Also the possible injection volumes need to be considered. The operating procedures of split injection and total sample transfer (splitless) differ according to whether there is partial or complete transfer of the solvent/sample on to the column. 

---