Discharge ionization current detector

摘要

A discharge ionization current detector using a low-frequency dielectric barrier discharge with an improved S/N ratio is provided. A current detector 20 is disposed between an excitation high-voltage power source 8 and a discharge electrode 5 to detect a discharge current flowing in pulses due to plasma generation. The detection signal of the current detector 20 and an output signal from a current amplifier 18 for amplifying an ion current are inputted into an output extraction unit 21. The output extraction unit 21 detects a precipitous-rise portion of the discharge current detection signal and generates a trigger signal, and then extracts an ion current signal for a predetermined time period from the trigger signal. This can remove an influence of a noise appearing in a signal during a time period where no plasma emission is generated, thereby improving the S/N ratio of the detection signal.

主权项

1. A discharge ionization current detector comprising:
a discharge generation means for generating plasma from a predetermined gas by electric discharge, including a pair of electrodes with at least one surface covered with a dielectric material and a voltage application means for applying a low-frequency AC voltage to the electrodes; a current detection means for detecting an ion current originating from a gas-phase sample component ionized by an action of the generated plasma; an emission timing detection means for detecting a timing of a plasma emission intermittently generated due to the electric discharge by the discharge generation means; and a signal extraction means for acquiring a signal corresponding to the ion current detected by the current detection means, for a time period from a substantive generation of the plasma emission to a time point which is set after a lapse of a predetermined time period from a termination of the plasma emission, the predetermined time period being determined by taking a lifetime of ions into account, based on the detection result by the emission timing detection means.