JP4966113B2 - Mercury atomic fluorescence analyzer - Google Patents

Description

  The present invention relates to a mercury atomic fluorescence analyzer that prevents scattering of ultraviolet rays from a mercury lamp.

  Conventionally, mercury analysis by atomic fluorescence has been performed. A gaseous sample is flowed into a flow cell made of quartz glass, the sample is irradiated with ultraviolet rays generated from a mercury lamp, and the fluorescence intensity of mercury generated from mercury atoms present in the sample is detected by a detector. Quantitative analysis is performed.

  However, in the conventional apparatus, the ultraviolet light incident from the entrance window of the flow cell made of quartz glass is scattered on the inner surface of the flow cell and the members surrounding the flow cell, and thus scattered light is generated. In particular, much scattered light was generated from the fixed surface of the fixing member fixing the flow cell. Therefore, the noise of the signal detected by the detector is large, the baseline is high, and it is difficult to detect mercury at a low concentration of 0.1 pg (picogram).

  The present invention has been made in view of the above-mentioned conventional problems, and provides a mercury atomic fluorescence analyzer that reduces scattered light from a flow cell, lowers the baseline of the signal detected by the detector and reduces noise, The purpose is to improve the analytical sensitivity and accuracy of the mercury atomic fluorescence spectrometer.

  In order to achieve the above object, a mercury atomic fluorescence analyzer of the present invention includes a mercury lamp that irradiates a sample with ultraviolet light, a detector that detects fluorescence of mercury generated from the sample, and ultraviolet light from the mercury lamp is incident. A cell is formed by a wall having an incident window, a wall having an exit window for emitting mercury fluorescence generated from a sample to the detector, a wall facing the entrance window, and a wall facing the exit window; A flow cell having an inlet for introducing a gaseous sample and an outlet for extracting a gaseous sample, and allowing the gaseous sample to pass therethrough, except for the entrance window and the exit window. The wall facing the entrance window and the wall facing the exit window have a flow cell covered with an ultraviolet absorber that absorbs ultraviolet rays or an ultraviolet antireflection material that prevents reflection of ultraviolet rays.

  “Covered with UV absorber or UV anti-reflective material” means that the inner and / or outer surface of the flow cell is encased in UV absorber or UV anti-reflective material to reduce scattered light generated in the flow cell, or It means that the flow cell itself is formed of an ultraviolet absorbing material or an ultraviolet antireflection material.

  According to the mercury atomic fluorescence analyzer of the present invention, the background caused by the scattered light superimposed on the detection signal of the detector by reducing the scattered light generated by the ultraviolet light incident from the mercury lamp being scattered in the flow cell. The signal can be greatly reduced, the baseline of the detection signal can be lowered, and the analytical sensitivity and accuracy of the mercury atomic fluorescence analyzer can be improved.

  In the mercury atomic fluorescence spectrometer of the present invention, the ultraviolet absorbing material and / or the ultraviolet antireflection material is preferably formed of a film, and the ultraviolet antireflection material is formed of magnesium fluoride or polyethylene terephthalate silicon. Is preferred.

  Hereinafter, a mercury atom fluorescence analyzer according to a first embodiment of the present invention will be described. As shown in FIG. 1, this apparatus includes a mercury lamp 10 that irradiates a sample S with ultraviolet rays 11, an incident slit 13 that narrows the luminous flux of ultraviolet rays emitted from the mercury lamp 10, a flow cell 20 that passes a gaseous sample, and a mercury lamp. 10 from the incident lens 15 that condenses the ultraviolet rays 11 from the flow cell 20 on the incident window 21, the fixing member 50 that fixes the flow cell 20, the detector 40 that detects the fluorescence 12 generated from the sample S, and the emission window 22 of the flow cell 20. An exit lens 16 that condenses the emitted fluorescence 12 on the detector window of the detector 40, an exit slit 17 that narrows the luminous flux of the fluorescence 12 that has passed through the exit lens 16, and a signal detected by the detector 40 to process the signal in the sample. A signal processing means 70 for quantifying the mercury content and a sample introduction unit 80 are provided.

  The mercury lamp 10 is, for example, a discharge tube in which mercury is enclosed. When the mercury lamp 10 is energized and discharged, it generates ultraviolet light having a wavelength of 253.7 nm which is a resonance line of mercury. The entrance lens 15 and the exit lens 16 are, for example, convex lenses made of fused silica, and the detector 40 is, for example, a photomultiplier tube. As shown in FIG. 2, the sample introduction unit 80 switches an argon cylinder 81 filled with an argon gas for introducing a gaseous sample, a mass flow meter 83 for controlling the flow rate of the argon gas, and a flow path of the argon gas. Three-way switching valve 84, filter 85 for removing mercury contained in argon gas, gaseous sample inlet 86, mercury collecting tube 87 for collecting mercury introduced from the sample inlet 86, gaseous sample The sample flow path 88 flows through, the bypass flow path 89 that bypasses the argon gas from the sample flow path 88, and the three-way joint 90 that connects the sample flow path 88 and the bypass flow path 89.

  When a gaseous sample is introduced with air, mercury in the sample is interfered and sensitivity is lowered. Therefore, argon gas is usually used as an introduction gas in order to increase the luminous efficiency of mercury. The filter 85 is a filter for removing a very small amount of mercury contained in the argon gas, and the container is filled with gold-coated sea sand, mercury-dedicated granular activated carbon, or the like. Similarly to the filter 85, the mercury collecting tube 87 has a container filled with gold-coated sea sand and a heating unit for releasing mercury collected from the sample.

  As shown in FIG. 3, the flow cell 20 has a shape of, for example, a square cylinder, and is formed of synthetic quartz having outer dimensions of 12 mm in length and width, 40 mm in height, and 1 mm in thickness. As shown in FIG. 4, the flow cell 20 is fixed so as to be surrounded by a fixing member 50 formed of, for example, an aluminum block, and is a cylindrical wall 23 that faces the mercury lamp 10 and is surrounded by the fixing member 50. The portion not formed forms the incident window 21 for allowing the ultraviolet light 11 from the mercury lamp 10 to enter, and the portion of the cylindrical wall 24 facing the photomultiplier tube 60 that is not surrounded by the fixing member 50 is generated from the sample. The emission window 22 for emitting the fluorescence 12 is formed.

  As shown in FIG. 4, the outer surface 25b of the cylinder wall 25 of the flow cell facing the entrance window 21 and the outer surface 26b of the cylinder wall 26 of the flow cell facing the exit window 22 are absorbed by an ultraviolet absorber 27, for example, a polyester film. It is covered with a UV absorbing film that has been subjected to metallic vapor deposition. As a commercial product of the ultraviolet absorber 27, there is an automotive window film manufactured by Mirareed. For example, an ultraviolet absorbing film may be attached to the outer surface 25b of the cylinder wall of the flow cell facing the entrance window 21 and the outer surface 26b of the cylinder wall of the flow cell facing the exit window 22, or fixed to face the outer surface 25b and the outer surface 26b. You may arrange | position so that it may be inserted | pinched between each surface of the member 50. FIG.

  5 is a cross-sectional view taken along the line II of FIG. 4 of the flow cell 20 to which the inlet joint 37 and the outlet joint 38 are connected. As shown in this figure, the flow cell 20 introduces the gaseous sample S. It has an outlet 35 and an outlet 36 through which the gaseous sample S is derived. Both the inlet 35 and outlet 36 are connected to an inlet joint 37 and outlet joint 38 made of tetrafluoroethylene via a sheet 39 of fluorocarbon rubber (Viton Rubber (registered trademark)) having a thickness of 1 mm. Is maintained. A sample inlet 80 (FIG. 2) is connected to the inlet joint 37, and a gaseous sample outlet (not shown) having a mercury collector for collecting mercury in the sample is connected to the outlet joint 38. Yes.

  Next, the operation of the mercury atomic fluorescence analyzer of the first embodiment will be described. As shown in FIG. 2, the argon gas discharged from the argon cylinder 81 is controlled to a predetermined flow rate by the mass flow controller 83 and is introduced into the three-way switching valve 84. When mercury measurement is not performed, the sample flow path 88 of the three-way switching valve 84 is closed, the bypass flow path 89 is opened, and the argon gas flows to the flow cell 20 from the three-way joint 90 via the bypass flow path 89. 20 is purged. When performing mercury measurement, the bypass flow path 89 of the three-way switching valve 84 is closed, the sample flow path 88 is opened, and the gaseous sample S introduced from the argon gas and the sample inlet 86 flows. Of mercury is collected in a mercury collecting tube 87. Thereafter, the mercury collecting tube 87 is heated by the heating part of the mercury collecting tube 87, and the collected mercury is introduced into the flow cell 20 as gaseous mercury.

  On the other hand, since the flow cell 20 is irradiated with the ultraviolet rays 11 from the mercury lamp 10, when gaseous mercury is introduced into the flow cell 20, fluorescence of 253.7 nm is generated from the mercury atoms. The fluorescence intensity of 253.7 nm is detected by the photomultiplier tube 40, the detection signal is processed by the signal processing means 70, and the mercury content in the sample is quantified.

  Next, the results of experiments using the apparatus of the first embodiment and the conventional apparatus will be described. In the flow cell of the conventional apparatus, the outer surface of the cylinder wall of the flow cell facing the entrance window and the outer surface of the cylinder wall of the flow cell facing the exit window are not covered with the ultraviolet absorber that absorbs ultraviolet rays. The apparatus of this embodiment and the conventional apparatus differ only in the flow cell, and the other configurations are the same apparatus. The results of measuring the same sample with the mercury amount of 45 pg (picogram) by operating both devices under the same measurement conditions as described above are FIGS. 6 to 11, and FIGS. 6 to 8 are the first embodiment. FIG. 9 to FIG. 11 show data measured with a conventional apparatus.

  6 and 9 show the profile of the signal voltage detected by the photomultiplier tube 40. As shown in FIG. 6, in the apparatus of the first embodiment, the base voltage is 0.2 V (volt). In the conventional device shown in FIG. 9, the base voltage is 4 V, and in the device of the first embodiment, the base voltage is reduced to 1/20. In the apparatus of the first embodiment, as shown in FIG. 4, the outer surface 25 b of the flow cell facing the entrance window 21 and the outer surface 26 b of the flow cell facing the exit window 22 are covered with the ultraviolet absorber 27 that absorbs ultraviolet rays. In addition, since the scattering of ultraviolet rays irradiated to the flow cell 20 from the mercury lamp 10 is suppressed and the scattered light is reduced, the base voltage is reduced to 1/20. On the other hand, in the conventional apparatus, since the flow cell is not covered with the ultraviolet absorber, a large amount of scattered light is generated, and the scattered light enters the photomultiplier tube 40 to increase the base voltage.

  FIGS. 7 and 10 both show signal intensity profiles obtained by processing the signal processing means 70 with the voltage obtained by subtracting the base voltage from the signal voltage. The signal strength is an arbitrary scale. The signal strengths shown in FIGS. 7 and 10 are both 7, which is almost the same. In order to make the noise levels of both devices easy to understand, FIG. 8 is an enlarged view of the skirt portion of the signal strength of FIG. 7, and FIG. 8 is an enlarged view of the heel portion of the signal strength of FIG. FIG. As shown in FIG. 8, in the apparatus of the first embodiment, the noise level is as low as 0.002, and there is almost no tailing (a state in which the skirt is pulled) in the signal intensity profile, but the conventional apparatus as shown in FIG. However, there is a lot of noise, the noise level is as high as 0.01, and the signal intensity profile is tailing.

  In the apparatus of the first embodiment, as shown in FIG. 4, the outer surface 25 b of the flow cell facing the entrance window 21 and the outer surface 26 b of the flow cell facing the exit window 22 are covered with an ultraviolet absorber 27 that absorbs ultraviolet rays. Since the scattering of the ultraviolet rays 11 irradiated to the flow cell 20 from the mercury lamp 10 is suppressed and the scattered light is reduced, the noise level is as low as 0.002 and the tailing of the signal intensity profile is almost eliminated. On the other hand, in the conventional apparatus, since the flow cell is not covered with the ultraviolet absorber 27, a large amount of scattered light is generated, the scattered light enters the photomultiplier tube 40, and a lot of noise is generated due to disturbance due to the scattered light. The noise level is as high as 0.01, and the tail of the signal intensity profile is wide tailed.

  In this field, the signal strength at the detection limit is generally defined as signal strength at the detection limit = 3 × noise level. Therefore, according to this equation, the signal strength at the detection limit of the device of the first embodiment and the conventional device. Is calculated, the detection limit signal intensity of the apparatus of the first embodiment is 0.006, and the detection limit signal intensity of the conventional apparatus is 0.03. The signal intensity obtained by measuring 45 pg mercury with the apparatus of the first embodiment and the conventional apparatus is both 7. When the detection limit value of the mercury amount is calculated from this signal intensity 7 and the signal intensity of the detection limit of both the above-mentioned apparatuses. In the apparatus of the first embodiment, it is 0.039 pg, and in the conventional apparatus, it is 0.19 pg. In the apparatus of the first embodiment, the sensitivity is improved 5 times as compared with the conventional apparatus.

  A mercury atomic fluorescence analyzer that is a second embodiment of the present invention will be described. The apparatus of the second embodiment is different from the apparatus of the first embodiment only in the flow cell, and the other configuration is the same apparatus, so only the flow cell will be described below. As shown in FIG. 12, the flow cell 100 is formed of the same square cylinder synthetic quartz as in the first embodiment, and is fixed so as to be surrounded by the same fixing member 50 as in the first embodiment. A portion of the cylindrical wall 103 facing the lamp 10 that is not surrounded by the fixing member 50 forms an incident window 101 through which the ultraviolet rays 11 from the mercury lamp 10 are incident, and a cylindrical wall 104 facing the photomultiplier tube 40 is formed. A portion not surrounded by the fixing member 50 forms an emission window 102 for emitting mercury fluorescence 12 generated from the sample. Ultraviolet absorbing material 107, for example, a polyester film subjected to metallic vapor deposition, absorbs ultraviolet rays by inner surface 105a of flow cell cylinder wall 105 facing entrance window 101 and inner surface 106a of flow cell cylinder wall 106 facing exit window 102. Covered with wood.

  In the apparatus of the second embodiment, the inner surface 105a of the cylinder wall of the flow cell facing the entrance window 101 and the inner surface 106a of the cylinder wall of the flow cell facing the exit window 102 are covered with the ultraviolet absorber 107 that absorbs ultraviolet rays. The same effect as the apparatus of the first embodiment can be obtained.

  A mercury atomic fluorescence analyzer that is a third embodiment of the present invention will be described. The apparatus of the third embodiment is different from the apparatus of the first embodiment only in the flow cell, and the other configuration is the same apparatus, so only the flow cell will be described below. As shown in FIG. 13, the flow cell 200 has the same square tube shape as that of the first embodiment, is fixed so as to be surrounded by the same fixing member 50 as that of the first embodiment, and the mercury lamp 10. The cylindrical wall 203 facing the cylindrical wall 203 is made of synthetic quartz and the portion not surrounded by the fixing member 50 forms an incident window 201 through which the ultraviolet rays 11 from the mercury lamp 10 are incident, and the cylindrical wall 204 facing the photomultiplier tube 40. Is a synthetic quartz, and a portion not surrounded by the fixing member 50 forms an emission window 202 for emitting mercury fluorescence 12 generated from the sample. A cylindrical wall 205 facing the entrance window 201 and a cylindrical wall 206 facing the exit window 202 are ultraviolet absorbers 207 that absorb ultraviolet rays, for example, an ultraviolet absorption filter STG-2050 manufactured by Annaka Special Glass Mfg. Co., Ltd., manufactured by Kenko Optical Shop. It is formed by processing a filter UV (L39), an ultraviolet absorption filter ITY-385 manufactured by Isuzu Seiko Glass, and the like.

  In the apparatus of the third embodiment, the cylindrical wall 205 facing the entrance window 201 and the cylindrical wall 206 facing the exit window 202 are formed of an ultraviolet absorbing material that absorbs ultraviolet rays, so that it is the same as the apparatus of the first embodiment. The effect of this can be obtained.

  A mercury atomic fluorescence spectrometer that is a fourth embodiment of the present invention will be described. The apparatus of the fourth embodiment and the apparatus of the first embodiment are different only in the flow cell, and the other configurations are the same apparatus, so only the flow cell will be described below. As shown in FIG. 14, the flow cell 300 is formed of the same square cylinder synthetic quartz as in the first embodiment, and is fixed so as to be surrounded by the same fixing member 50 as in the first embodiment. A portion of the cylindrical wall 303 facing the lamp 10 that is not surrounded by the fixing member 50 forms an incident window 301 through which the ultraviolet rays 11 from the mercury lamp 10 are incident, and a cylindrical wall 304 facing the photomultiplier tube 40 is formed. A portion that is not surrounded by the fixing member 50 forms an emission window 302 for emitting mercury fluorescence 12 generated from the sample.

  An inner surface 305a and an outer surface 305b of the cylindrical wall 305 of the flow cell facing the entrance window 301 and an inner surface 306a and an outer surface 306b of the cylindrical wall 306 of the flow cell facing the exit window 302 prevent UV reflection, for example, fluorination The film is covered with an ultraviolet antireflection film 307 deposited with magnesium. A film having a thickness of 0.4 mm formed of polyethylene terephthalate silicon or a commercially available ultraviolet antireflection film may be attached as the ultraviolet antireflection material 307.

  In the apparatus of the fourth embodiment, the inner surface 305a and the outer surface 305b of the cylindrical wall of the flow cell facing the entrance window 301 and the inner surface 306a and the outer surface 306b of the cylindrical wall of the flow cell facing the exit window 302 prevent ultraviolet reflection. Since it is covered with the prevention member 307, the same effect as the apparatus of the first embodiment can be obtained.

  In the first to third embodiments, the flow cell is covered with the ultraviolet absorbers 27, 107, and 207, but may be covered with an ultraviolet antireflection material. In the fourth embodiment, the ultraviolet antireflection material 307 is used, but an ultraviolet absorber may be used. In the first to fourth embodiments, the cylinder walls 25, 105, 205, 305 of the flow cell facing the entrance windows 21, 101, 201, 301 and the cylinder walls of the flow cell facing the exit windows 22, 102, 202, 302 are shown. 26, 106, 206, and 306 were covered with the ultraviolet absorbers 27, 107, and 207 and the ultraviolet antireflection material 307. In addition to these cylindrical walls, the wall 23 having incident windows 21, 101, 201, and 301 was also added. , 103, 203, 303 other than the entrance windows 21, 101, 201, 301 and the walls 24, 104, 204, 304 having the exit windows 22, 102, 202, 302 other than the exit windows 22, 102, 202, 302 This region may be covered with an ultraviolet absorbing material or an ultraviolet antireflection material.

  The shape of the flow cell is not limited to a square cylinder, and may be a rectangular cylinder, a cylinder, or an elliptic cylinder, or may not be a cylinder, and may be a hollow cube, a sphere, an ellipsoid, or the like. Moreover, you may form the entrance window and exit window which protruded in a part of these shapes. The inlet joint 37 and the outlet joint 38 may be formed integrally with the flow cell.

  In the embodiment, the non-dispersion type mercury atom fluorescence analyzer has been described. However, a wavelength dispersion type mercury atom fluorescence analyzer may be used. Moreover, although the apparatus which measures by the batch system using a mercury collection tube was demonstrated, it is an apparatus which measures by another system with another batch system, or an apparatus which measures by a continuous system while flowing a gaseous sample to a flow cell. The same effect as the apparatus can be obtained.

1 is a schematic block diagram of a mercury atomic fluorescence analyzer that is a first embodiment of the present invention. FIG. It is a schematic block diagram of the sample introduction part of the same apparatus. It is a perspective view of the flow cell of the same device. It is a top view of the flow cell of the same device. It is the II sectional view taken on the line of FIG. It is the profile of the signal voltage by the same apparatus. It is the profile of the signal strength by the same apparatus. It is a noise level profile of the signal strength by the same apparatus. It is the profile of the signal voltage by the conventional mercury atom fluorescence analyzer. It is the profile of the signal strength by the same apparatus. It is a noise level profile of the signal strength by the same apparatus. It is a top view of the flow cell of the mercury atom fluorescence analyzer which is 2nd Embodiment of this invention. It is a top view of the flow cell of the mercury atom fluorescence analyzer which is 3rd Embodiment of this invention. It is a top view of the flow cell of the mercury atom fluorescence analyzer which is 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mercury lamp 11 Ultraviolet 12 Mercury fluorescence 20 100 200 300 Flow cell 21 101 201 301 Entrance window 22 102 202 302 Outgoing window 23 103 203 303 Wall having entrance window 24 104 204 304 Wall having exit window 25 105 205 305 Entrance window Wall 106 106 206 306 Wall facing the exit window 27 107 207 Ultraviolet absorber 35 Inlet 36 Outlet 40 Detector 307 Ultraviolet antireflection material S Sample

Claims (2)

A mercury lamp that irradiates the sample with ultraviolet light;
A detector for detecting fluorescence of mercury generated from the sample;
A wall having an entrance window for receiving ultraviolet light from the mercury lamp, a wall having an exit window for emitting mercury fluorescence generated from a sample to the detector, a wall facing the entrance window, and a wall facing the exit window A flow cell having an inlet for introducing a gaseous sample into the cell and an outlet for extracting a gaseous sample, the gas passing through the gaseous sample, except for exit window, the flow cell at least said entrance window and the opposite wall and the exit window and the opposite wall is covered with an ultraviolet absorber that absorbs ultraviolet light,
Mercury atomic fluorescence spectrometer. 2. The mercury atom fluorescence analyzer according to claim 1, wherein the ultraviolet absorber is formed of a film.

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