Direct Sample Introduction System For Capillary Columns

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Abstract
The precolumn inlet is designed for direct sampling into high resolution packed and capillary columns. The entire injected amount of sample is fed as a narrow plug of true composition to the column with no portion of the sample material being lost as in the conventional splitting procedure. The discrepancy between the allowed minute sample size for a capillary column and the smallest amount which can be reproducibly handled by a microliter syringe is bridged by diluting the sample in an appropriate solvent. Preferably, a non-volatile solvent like silicone oil is used. The diluted sample is gathered into a syringe and introduced into the small, easily interchangeable, packed glass precolumn in the inlet. The sample evaporates from the silicone oil and is fed to the column. The precolumn inlet also includes a refrigeration device in the lower part of the unit. Sample components spread over a too large volume of carrier gas are trapped in a narrow zone at the very top of the chromatographic column. When the cooling fluid is turned off, the cold zone rapidly heats and releases the sample as a sharp plug into the column.

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