US-12618778-B2 - Gas chromatography combustion furnace/tube structure for a sulfur chemiluminescence detector

Abstract

In a sulfur chemiluminescence detector (SCD) including a heating furnace 210 including a combustion tube 211 and a heating means 215 for heating the combustion tube 211 , an inert-gas introduction tube 214 that has the front end inserted into an end portion on an inlet side of the combustion tube 211 and has the rear end into which an end portion on the outlet side of a column 140 of a gas chromatograph is inserted, and inert-gas supplying means 264, 221 , and 251 for supplying inert gas into the inert-gas introduction tube 214 in a manner that the inert gas flows from the rear end to the front end are provided. The inert gas (for example, nitrogen) flowing through the inert-gas introduction tube 214 can prevent the end portion on the outlet side of the column 140 from being exposed to oxygen. In this manner, generation of column bleeding caused by a decomposition product of the liquid phase can be suppressed, so that a decrease in the sensitivity of the SCD can be suppressed.

Inventors

• Takamasa Suzuki

Assignees

• SHIMADZU CORPORATION

Dates

Publication Date

20260505

Application Date

20181220

Claims (2)

1. 1 . A sulfur chemiluminescence detector comprising: a heating furnace including a combustion tube and a heating means for heating the combustion tube; an inert-gas introduction tube having a front end configured to be inserted into an end portion on an inlet side of the combustion tube and having a rear end configured so that an end portion on an outlet side of a column of a gas chromatograph is inserted; an oxidizing-agent supply configured to supply an oxidizing-agent into the combustion tube; and an inert-gas supply configured to supply inert gas into the inert-gas introduction tube in a manner that the inert gas flows from the rear end to the front end, wherein a tip of an end portion on the outlet side of the column is located at a position retracted from the front end of the inert-gas introduction tube inside the inert-gas introduction tube.
2. 2 . The sulfur chemiluminescence detector according to claim 1 , wherein the inert gas is nitrogen.

Description

TECHNICAL FIELD The present invention relates to a sulfur chemiluminescence detector. BACKGROUND ART The sulfur chemiluminescence detector (SCD) is capable of detecting a sulfur compound in a sample at high sensitivity by using chemiluminescence, and is usually used in combination with a gas chromatograph (GC) (see Patent Literature 1, for example). Gas containing sample components (sample gas) separated in a column of the GC is introduced into a heating furnace provided in the SCD. The heating furnace includes a combustion tube and a heater for heating the combustion tube. The sample gas is oxidized while passing through the combustion tube, and sulfur dioxide (SO2) is generated from a sulfur compound in the sample gas. Furthermore, the SO2 is reduced while passing through the combustion tube, and sulfur monoxide (SO) is generated from the SO2. The SO is introduced into a reaction cell provided in the subsequent stage of the heating furnace and mixed with ozone (O3) in the reaction cell. The reaction of SO and O3 produces an excited species (SO2*) of sulfur dioxide. When the SO2* turns back to the ground state through chemiluminescence, the emission intensity of the SO2* is detected by a photodetector, and thus the quantity of the sulfur compound contained in the sample gas is detected from the emission intensity. CITATION LIST Patent Literature Patent Literature 1: JP 2015-59876 A SUMMARY OF INVENTION Technical Problem When the SCD is used in combination with the GC as described above, gas chromatography is performed in a state where an outlet end of the column of the GC is inserted into an inlet of the combustion tube in the heating furnace of the SCD. At this time, the temperature near the inlet of the combustion tube is about 450 to 500° C. However, the heat-resistant temperature of a general GC column is about 400° C.; and it is known that, when the GC column is used over the heat-resistant temperature, a part of the stationary phase (usually liquid phase) of the column is decomposed and a decomposition product (cyclic siloxane, and the like) elutes from the column to generate a background signal called column bleeding. Since this column bleeding deteriorates the SN ratio and causes a decrease in the sensitivity of the SCD, an effective measures for reducing the column bleeding is required. The present invention has been developed in view of the above points, and an object of the present invention is to provide an SCD capable of reducing column bleeding and minimizing a decrease in the sensitivity due to the column bleeding. Solution to Problem A sulfur chemiluminescence detector (SCD) according to the present invention developed to solve the above problem includes: a heating furnace including a combustion tube and a heating means for heating the combustion tube:an inert-gas introduction tube having a front end configured to be inserted into an end portion on an inlet side of the combustion tube and having a rear end configured so that an end portion on an outlet side of a column of a gas chromatograph is inserted; andan inert-gas supplying means configured to supply inert gas into the inert-gas introduction tube in a manner that the inert gas flows from the rear end to the front end. Cyclic siloxane, which causes column bleeding, is produced in a case where a liquid phase of the column is exposed to oxygen at high temperatures. Oxygen (or air) is introduced into the combustion tube of the heating furnace as an oxidizing agent to oxidize sample gas eluted from the column. In a conventional SCD, an end portion on the outlet side of a column (GC column) of a gas chromatograph is directly inserted into an end portion on the inlet side of a combustion tube. For this reason, a liquid phase of the GC column is exposed to oxygen inside the combustion tube, resulting in column bleeding. In contrast, in the SCD according to the present invention, the front end of the inert-gas introduction tube is inserted into the end portion on the inlet side of the combustion tube, and the end portion on the outlet side of the GC column is inserted into the rear end of the inert-gas introduction tube. Since the inert gas flows through the inert-gas introduction tube from the rear end to the front end, with the tip of the end portion on the outlet side of the GC column being located inside the inert-gas introduction tube, the liquid phase of the GC column is not exposed to oxygen present in the combustion tube. As a result, the occurrence of column bleeding can be suppressed in the SCD according to the present invention. It is desirable to use nitrogen as the inert gas in the present invention. Other inert gas (for example, helium) can also be used. In the sulfur chemiluminescence detector according to the present invention, the tip of the end portion on the outlet side of the column is preferably located at a position retracted from the front end of the inert-gas introduction tube inside the inert-gas introduction tube. Adv