Inlet liner diameter

Figure 4.12. Effect of inlet liner diameter on SPME injection of hydrocarbons, (a) 4-mm-diameter liner (b) 2-mm-diameter liner (c) 0.75-mm-diameter liner. Analytes 1, octane 2, decane 3, undecane 4, tridecane 5, tetradecane 6, pentadecane. [Reprinted with permission from Ref. 44 (Fig. 3). Copyright Advanstar Communications.]...

A GC inlet liner of low volume should transfer desorbed analytes to the chromatographic column inlet. The effect of the inlet liner diameter on the broadening of VOCs peaks is reported by Okeyo and Snow [179]. Peak broadening of the most volatile compoimds is avoided using smaller diameter liners. Less volatile compoimds are not broadening and the peaks are not affected by the liner diameter. 

FIGURE 11.22 Effect of inlet liner diamete on SPME injection of hydrocarbons (a) 4-mm-i.d. liner (b) 2-mni-i.d. liner (c) 0.75-mm-i.d. liner [reprinted with permission from P. Okeyo and N. H. Snow, LC/GC 15, (1997) 1130-1136 (1997), Figure 3 copyright 1997, Advanstar Publications]. 

Another very flexible solution for numerous applications in pyrolysis, outgassing or thermal extraction experiments is the use of a micro-furnace, which can be resistively heated to temperatures above 1000 C (Roussis and Fedora, 1998). The sample is placed in a small, low, thermal mass cup of 50-80 pL volume, which is dropped into the heated pyrolysis furnace consisting of a vertical quartz tube. The furnace tube size is comparable to a GC inlet liner with 4.5 mm inner diameter and 12 mm length and allows programmable temperature profiles with heating rates of up to 200 C/min (Frontier Laboratories Ltd., Japan). 

For hot injectors capillary columns with an internal diameter of 0.32 mm are more suitable, as the transfer of the sample from the inlet liner to the column takes place more rapidly with less diffusion. However, on coupling with MS detectors, the higher column flow rate can exceed the maximum compatible flow rate in some quadrupole MS systems, and need to be checked. Columns with an internal diameter of 0.25 mm are the popular alternative and should be used in hot injectors with 2 mm internal diameter inserts and low injection volumes to obtain optimal results. If inserts with a wide internal diameter of4 mm are used for larger injection volumes, the solvent effect must be particularly exploited for focusing (Figure 2.67). 

Use the correct liner for an injection mode select the inner diameter of a liner to be commensurate with solvent boiling point, solvent expansion, and injection volume when employing a vaporizing inlet. 

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