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INCREASING INSTRUMENT-TO-INSTRUMENT TEMPERATURE REPEATABILITY IN GC CONDUCTION OVEN

IP.com Disclosure Number: IPCOM000249681D
Publication Date: 2017-Mar-17

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INCREASING INSTRUMENT-TO-INSTRUMENT TEMPERATURE REPEATABILITY IN GC CONDUCTION OVEN

This article discloses an improved sensor mounting in a conduction heating apparatus of planar configuration for heating a gas chromatography (GC) column.

I.          Background

Gas chromatography (GC) entails the analytical separation of a vaporized or gas-phase sample that is injected into a chromatographic column configured for GC (a “GC column”).  A chemically inert carrier gas, such as helium, nitrogen, argon, or hydrogen, is utilized as the mobile phase for elution of the sample in the column.  The sample and carrier gas are introduced into a GC inlet coupled to the column head.  In the GC inlet, the sample is injected into the carrier gas stream and the resulting sample-carrier gas mixture flows through the column.  This is referred to as column flow.  During column flow the sample encounters a stationary phase (typically a material lining the inside surface of the column), which causes different components of the sample (or “analytes,” e.g., different chemical compounds) to separate according to different affinities with the stationary phase.  The separated components elute from the column exit and are measured by an appropriate detector, producing data from which a chromatogram or spectrum identifying the components may be constructed.  The amount of time required for a chemical compound to traverse the entire length of a separation column (“column”) is known as its retention time.  An example of a chromatogram conducted from the detector signal is a plot of signal intensity as a function of retention time, with the trace having a series of peaks at respective retention times.  Each peak corresponds to a detected chemical compound that eluted from the column at a specific retention time.

While the sample flows through the column, the column (and thus the sample) is maintained at a desired temperature.  For this purpose, the column is typically housed in a thermally-controlled convection oven (e.g., air convection oven) or positioned in thermal contact with a heating device.  Temperature-programming the column allows a wider range of components to be analyzed in a single sample run.  If a temperature program is used, the column is typically cooled down to the method start temperature in between sample runs.  In GC systems, the temperature of the column is one factor that contributes to the retention time of a chemical compound.  Controlling the temperature of the column precisely from analysis to analysis is beneficial to provide repeatability in the retention time for a particular chemical compound.  In addition, programmatically changing the column temperature while the sample analytes are migrating through the column can advantageously provide shorter analysis time and reduce peak broadening.

A convection oven is often selected as the means for heating a column because the oven is able to provide a uniform and rep...