The Dow Chemical Company

Joseph F Hiller

Terrence McCabe

Paul L Morabito

Richard G Melcher

Thomas L Peters

Glen H Hughes

Daniel P Martin

Method and apparatus for gas chromatography/mass spectroscopy including a retention gap, a capillary gas chromatography column and a mass spectrometer, the improvement being a valve that facilitates temporarily venting the carrier gas from between the retention gap and the capillary gas chromatography column immediately after the injection of a sample. The valve also facilitates an alternate flow of carrier gas into the mass spectrometer during the venting operation.

Vented capillary gas chromatography apparatus

Apparatus and method for temperature gradient capillary gas chromatography wherein the chromatography column is surrounded by an inner tube and the inner tube is surrounded by an outer tube. A first heat transfer fluid is heated to a first temperature and is flowed between the inner tube and the column in the same direction as the flow of carrier gas through the capillary column. A second heat transfer fluid is heated to a second temperature and is flowed in the opposite direction between the outer tube and the inner tube, the second temperature being lower than the first temperature. The invention is also an improved capillary gas chromatography method of the type that generally includes the steps of flowing a carrier gas through a capillary gas chromatography column to a detector, introducing a sample to be analyzed into the column and then detecting chromatographically resolved components of interest of the sample, the method having an optimum carrier gas velocity through the column, wherein the improvement of the instant invention is to establish a negative temperature gradient along at least a portion of the longitudinal length of the capillary gas chromatography column and to flow the carrier gas through the capillary gas chromatography column at less than the optimum carrier gas velocity.

Apparatus and method for establishing a temperature gradient in a

The invention describes a large volume on-column gas chromatographic method for analyzing trace levels of high molecular weight and polar compounds in a sample and an apparatus for performing the method. A column inlet coupled to an analytical column is heated rapidly to concentrate difficult to chromatograph compounds onto the analytical column resulting in an increase in the detectability of the compounds.

Heated column inlet gas chromatography method and apparatus

A method for on-column injection of large sample volumes using the retention gap technique in capillary gas chromatography for sample components of interest that would be obscured by the large solvent peak otherwise inherent in the technique. This interference from the large solvent peak is removed by venting carrier flow from the retention gap to waste for a limited time, long enough to discard much of the solvent without serious loss of the sample component of interest.

Vented retention gap capillary gas chromatography method

In one embodiment the invention is a method for on-column valved injection gas chromatography by on-column injecting more than 5 microliters and less than one milliliter of sample consisting of a solvent and a component of interest into a retention gap/capiliary column system with an injection valve at a first carrier gas flow rate, followed by a substantially higher carrier gas flow rate to blow the solvent of the sample out of the system at a rapidly increased rate and then a return to a lower flow rate to chromatograph the component of interest. In another embodiment, less than 5 microliters of sample consisting of a solvent and a component of interest is on-column injected into a capillary column using an injection valve and a relatively high column inlet pressure of gas to move the sample from the injection valve into the colunm rapidly and with reduced carryover. Then, the pressure of carrier gas is reduced to a normal pressure for chromatography of the component of interest.

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Midland, MI, United States of America

Joseph F Hiller