Discharge ionization current detector

Abstract

The invention relates to a discharge ionization current detector. A technique for reducing an electromagnetic noise entering an electrode or a drift of a signal due to a fluctuation in the ambient temperature is provided to improve the S / N ratio of a signal originated from a component of interest. A dummy electrode 11 having the same structure as an ion-collecting electrode 10 is provided within a lower gas passage 14 at a position where dilution gas with no sample gas mixed therein flows. A differential amplifier 24 is provided to perform differential detection between an output end A of a current amplifier 21 connected to the ion-collecting electrode 10 and an output end B of a current amplifier 22 connected to the dummy electrode 11. The detected differential signal is free from a common mode noise or a drift and hence accurately reflects the amount of the component of interest.

Description

technical field [0001] The present invention relates to a discharge ionization current detector suitable primarily as a gas chromatography (GC) detector, and more particularly to a discharge ionization current detector using a low frequency barrier discharge. Background technique [0002] As gas chromatography detectors, such as thermal conductivity cell detector (TCD), electron capture detector (ECD), flame ionization detector (FID), flame photometric detector (FPD) and flame thermionic detector have been practically used (FTD), etc. of various types of detectors. Among these detectors, the FID is the most widely used, especially for the detection of organic substances. FID is a device that uses a hydrogen flame to ionize the sample components in the sample gas and detects the resulting ion current. The FID can achieve a wide dynamic range of about 6 orders of magnitude. However, the FID has the following defects: (1) The ionization efficiency of the FID is low, which ma...

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Problems solved by technology

However, FID has the following defects: (1) The ionization efficiency of FID is low, which makes the minimum detectable amount of FID not low enough

(2) The ionization efficiency of FID for alcohols, aromatic substances and chlorine-containing substances is low

(3) FID needs hydrogen as a highly dangerous substance, so it must be equipped with explosion-proof equipment or similar special equipment, which makes the whole system more difficult to operate

However, it is difficult to completely eliminate the influence of electromagnetic noise entering the ion-collecting electrodes

It is also difficult to prevent the detection signal from drifting due to fluctuations in the ambient temperature near the detection unit, which may be heated up to about 400 degrees Celsius in order to detect high boiling point components

If a GC detector or similar detector is operated continuously for a considerable period of time during the measurement period, the aforementioned noise or drift causes baseline fluctuations in the detected signal and thereby causes a decrease in the S / N ratio of the signal resulting from the component of interest

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