SU1000905A1 - Combination flame detector for gas chromatography - Google Patents

Description

one

The invention relates to gas chromatography, in particular to detectors, and can be used for the simultaneous selective analysis of hydrocarbons, halogens and compounds containing nitrogen, phosphorus and sulfur.

A flame selective photometric detector is known for detecting compounds containing sulfur, phosphorus, and chlorine, containing two burners built in one another and three corresponding light filters connected to photoelectric multipliers (PMTs).

The detector is adapted to select, 5, and locate S-, P- and C1-containing substances, but does not analyze nitrogen-containing substances and hydrocarbons.

A two-flame thermionic detector for the simultaneous determination of hydrocarbons, halogens, N- and P-containing compounds, including the upper and lower burners with 1} electrodes, is also known.

This detector is structurally complex and requires the analysis of halogen, N- and P-containing substances source of salts of alkali metals.

The closest in technical essence to the present invention is a detector, comprising a housing in which a lower burner with a positive power electrode and a signal electrode, an additional upper burner with a negative power electrode and a cylindrical collector electrode are located.

This detector is simple structurally and does not require alkali metal salts 2 for the selective determination of halogens, N- and P-containing compounds.

A disadvantage of the known detector is the inability to selectively determine sulfur-containing substances. In addition, the annular feed electrode above the upper burner is mainly affected by residual compounds rising from the lower burner, and therefore with the introduction of large samples of hydrogenogens, nitrogen and phosphorus-containing compounds, it partially loses its ionization properties, which leads to a decrease in the sensitivity of the analysis. The relatively large inner diameter of the detector and the possibility of passage of ionized compounds (their derivatives) from the outside of the upper cylindrical collector electrode also lead to a decrease in sensitivity due to washing out of the connections in the working volume between the lower and upper burners and their incomplete capture by the collector electrode. The purpose of the invention is to increase the selectivity and sensitivity of the analysis of halogens and compounds containing nitrogen, phosphorus, sulfur. This goal is achieved by the fact that a dual-flame detector, comprising a housing in which a lower burner with a positive power electrode and a signal electrode, zs

an additional top burner with a negative supply electrode and a cylindrical collector electrode, a transparent quartz bushing placed around the top burner, with a slot through which a negative electrode placed in the zone of maximum heating of the flame, a successively installed photomultiplier tube and a light guide located on the outside of the bushing in the flame zone the upper burner is perpendicular to its axis and the negative electrode, and the cylindrical collector electrode is densely installed The diameter of the quartz tube is new. I The increase in the specificity of the determination for sulfur-containing compounds is achieved by installing a fiber in the zone of the upper flame, connected via a light filter with a photomultiplier. A quartz sleeve made of fused transparent quartz protects the light guide from overheating, and, due to its high thermal insulation properties, the temperature in the upper supply electrode is maintained more evenly throughout the diameter of the detector, which increases and stabilizes the ionic electrons. The sensitivity of the analysis is increased by placing the top 10

Claims (2)

on the upper metal burner 7, above the exit of which, in the zone with the maximum flame temperature, a nickel negative power supply electrode 8 is installed through the slot in the sleeve. A cylindrical collector electrode 9 is fixed in the quartz sleeve above the electrode 8. In the upper part of the detector there is a coil 10 for igniting the flame on the burners. The detector ends with a removable cover 11. On the outer side of the quartz sleeve in a zone symmetrically covering the flame, perpendicular to the last direct supply electrode is placed directly in the hydrogen flame, reducing the detector working volume and passing all ionized connections (their derivatives) inside the collector. A reduction in the working volume of the detector is achieved by installing a quartz sleeve, which allows a collector electrode to be placed tightly along its internal diameter, eliminating the possibility of the electrode contacting with the housing while reducing the diameter of the detector. FIG. 1 shows the proposed detector, longitudinal section; in fig. 2A-A in FIG. 1. The detector contains a detachable housing 1, in the lower part of which, in the base of the research institute 2, a lower metal burner 3 is installed, above which the annular positive supply electrode and the signal electrode 5 above it are placed. The signal electrode 5 is located above the signal electrode 5 in the center of the transparent quartz bushing 6 L-shape and electrode 8 flexible light guide 12, connected through a light filter 13 with a photomultiplier tube 1A. Hydrogen and carrier gas (nitrogen) to the burner 3 is supplied through the base 2, and the air through the opening in the lower part of the body. Example. The proposed detector was tested on a Color brand chromatograph for analyzing a mixture of С-Су hydrocarbons, ethyl alcohol, acetonitrile, hydrogen sulfide and sulfur dioxide. The analysis was carried out on a one-meter chromatographic column filled with Polysorb-1 (fraction 0.50, 8 mm) at 110 °. The evaporator was heated until. Before analyzing, we measured with the help of soap-film gumoscule, measure the flux lines through the detocg) | ;. mln-mpn: Skyrheg of hydrogen entering the lower burner of the detector30 The speed of hydrogen entering the top burner of the detector kQ. Speed of air flow into the detector Speed of carrier gas (nitrogen) 50 Before the photomultiplier after the fiber, an interference filter with a transmission wavelength of 395 nm is installed (for sulfur-containing compounds). Spiral 10 was ignited, the hydrogen flame on both burners, 10–15 min after the detector was heated, the analysis was started. By means of a syringe, through an evaporator chromatograph, an air sample with the analyzed mixture was injected onto the chromatographic column and the outgoing separated-compounds were fixed by the detector. A signal from a mixture of hydrocarbons C, -Cg of ethanol and acetonitrile was recorded from the lower burner. Only the signal from acetonitrile was recorded from the upper collector electrode. The signal amplified after the PMT recorded hydrogen sulfide, sulfur dioxide and acetonitrile. The signal from acetonitrile, obtained from the upper collector electrode, is 1.5 times more than the signal recorded after the photomultiplier. Thus, a selective two-flame detector makes it possible to simultaneously determine not only the P – N and C 1 content of the compound, but also sulfur-containing substances. The threshold sensitivity of nitrogen-containing compounds to acetonitrile is 10 mg of halogen-containing methylene chloride and 8 to 10 mg of sulfur-containing hydrogen sulfide. An increase (by a factor of k) in the detection of halogens and nitrogen-containing compounds is achieved by increasing the ionization from the nickel electrode located in the zone of maximum heating, the entry of all ionized compounds into the collector electrode, and reducing the internal diameter of the detector to 7 mm, i.e. in 2-2,3 razl in comparison with prjuotyp. Reducing the diameter of the detector and, accordingly, the working volume between the lower and upper burners, reduces the smearing of the components and provides more symmetrical chromatographic peaks recorded from the upper signal electrodes, which allows working with lower carrier gas velocities. Placing the upper nickel feed electrode directly in the hydrogen flame zone reduces its poisoning when large samples of N-, P-, C1- and S-containing compounds get in, which contributes to the stabilization of its ionizing effect. This improves the accuracy of the determination of the analyzed substances. The quartz sleeve not only protects the fiber from overheating, but also eliminates the possibility of contact of the precisely fixed collector electrode with the housing or the upper supply electrode. The light filter installed after the fiber can be easily replaced with a filter with a different transmission wave if it is necessary to fix the connections of some other classes. The proposed detector, in comparison with the known ones, has a high selectivity and sensitivity of the analysis, which allows expanding the possibilities of identifying various classes of compounds in a complex mixture. Claims Two-flame detector for gas chromatography comprising a housing in which a lower burner with a positive power electrode and a signal electrode, an additional upper burner with a negative power electrode and a cylindrical collector electrode, are located, characterized in that, in order to increase the selectivity and sensitivity of the halogen analysis and compounds containing nitrogen, phosphorus and sulfur, a transparent quartz bushing with a slot, placed around the upper burner, is introduced into it oruyu maximum flame in the heating zone is placed a negative electrode sequentially installed photomultiplier tube and optical fiber located on the outside of the quartz sleeve in the flame zone of the burner top perpondi710009058 its axis and negative electrically are 1. Mac-Zeir G., Bonelli E. Vvederode, and the cylindrical collector ones into gas chromatography. M., World, the electrode is tightly mounted internally 1970, p. 111-112. him the diameter of the quartz sleeve. 2. USSR author's certificate Sources of information, SN, cl. G 01 N 31/08, 1979 taken into account in the examination (prototype).