SU1312480A1 - Photoionization detector - Google Patents

Abstract

The invention relates to a physicochemical, in particular, chromatographic analysis, and can be used as a detection device in various chromatographs or analyzers. The purpose of the invention is to improve the accuracy of the analysis and reduce the detection limit. The device is equipped with a photoemission cell, located coaxially with the ionization chamber. The photoemission cell is equipped with gas supply and discharge channels and a plate of transparent material separated from the ionization chamber. One of the electrodes of the photoemission cell is located in its bottom part, and the other on its lateral inner surface. 3 il. with

Description

113

The invention relates to physicochemical, in particular, chromatographic analysis, in particular to photoionization detectors used in gas chromatographs.

The aim of the invention is to reduce the detection limit and increase the accuracy of the analysis.

Fig. 1 shows a photonization detector; figure 2 is a section in figure 1; on fig.Z - block diagram of the device.

The photoionic detector consists of a gas discharge lamp 1, which is a source of ultraviolet radiation (for example, a glow discharge CRPM type KRPM lamp), filled with window 2 of MgF fluoride single crystal, ionization chamber 3, and a photoemission cell 4.

The enclosures of the ionization chamber 5 and the photoemission cell 6 (in this design cylindricalJ are made of high-alumina ceramic type VK-100 providing low leakage currents. The input window 7 of the ionization chamber and the common separating plate 8 are made of transparent material (MgFj or LiF single crystals) Polarizing 9 and collector 10 electrodes of the ionization chamber are made in the form of cylindrical segments connected to inlet 11 and outlet 12 capillaries through electrically isolating sleeves 13 and 14 of high-alumina core The polarizing voltage is supplied and the signal is removed from the electrodes 15 and 16 connected to the corresponding electrodes of the inner chamber.

The anodic electrode 17 of the photoemission cell is connected to contact 18. The photocathode 19, which is also the sealing element of the cell, is connected to contact 20. Between the discharge lamp window and the input window of the ionization chamber is a metal screen 21. For pumping the photoemission cell inert and gassed , filling or evacuating serve as gas capillary inlet 22 and outlet .23 (Figure 2).

The photoionization detector is connected according to the block diagram shown in FIG.

The ionization chamber 3 is connected to an ionization amplifier 24.

02

the camera, the polarizing electrode 9 being connected to the power supply located in the amplifier unit, and the collector electrode 10 to the amplifier input. The photoemission cell 4 is connected to the emission cell amplifier 25, and the photocathode 19 is connected to the power supply in the present amplifier unit, and the anodic one

the electrode 17 is connected to the amplifier input. The outputs from both amplifiers are connected to the input of the signal processing unit 26, the signal from which is fed to the recorder.

The detector works as follows.

A carrier gas is continuously passed through the ionization chamber 3. The luminous flux of the lamp 1 through the window 2

the lamp and the entrance window 7 of the ionization chamber enter the ionization chamber, where, due to the ionization of gas impurities and photoemission from the surfaces, a zero-line current is created

if, is the proportion of the luminous flux f. When an analyzed sample enters the detector due to its ionization, an additional current appears equal to A. All this time through

photoemission cell 4 passes clean gas, not subject to ionization by ultraviolet radiation (UV). In this case, the luminous flux of the lamp 1 through the ionization chamber 3 and the total

the separating plate 8 hits the photocathode 19, knocks out the photoelectrons and creates an emission current proportional to the luminous flux f. Measurement of photoemission cell current

I want to get --- at any time

F

time and thereby get the value of the correction to the signal. Thus, using the proposed device, a signal is obtained, corrected for the additional contribution from the fluctuation. luminous flux which can be represented as

 . LF Corr A + 1o -f-

Claims (1)

From this formula, it can be seen that, since, using the proposed device, the influence on the magnitude of the signal of the fluctuations of the light flux is eliminated, the accuracy of the analysis is improved and the detection limit is lowered. Photoionization detector containing ionization chamber with KA3131 The electrodes located around the periphery of the chamber, the gas-discharge resonant lamp separated from the ionization chamber by a transparent plate, and the recorder, characterized in that, in order to improve the accuracy of the analysis and reduce the detection limit, ok is equipped with a comparative photoemission cell located coaxially with the ionization chamber and separated from it by a second transparent plate. 24804  located parallel to the first plate, provided with channels for supplying and receiving gas and two electrodes, one of which is located 5 parallel to the transparent plates in the cross section of the light beam and is the bottom of the photoemission cell, and the other is outside the light beam on the photoemission wall, W and both cells are connected in parallel through the signal comparison unit to the recorder. entrance 20 Bibiws 1 , 15 21 P 26 Krpistm W3 Editor G. Volkova Compiled by L.Zharkova Tehred L. Serdyukova Proofreader L. Patay. 1967/43 Tmrazh 777. Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4