JP4333542B2 - ICP emission analyzer - Google Patents

Description

  The present invention relates to ICP (High Frequency Inductively Coupled Plasma) emission analysis.

  In the ICP emission analyzer, a liquid sample is atomized by a nebulizer to form a sample aerosol, which is introduced into a plasma torch together with argon gas. An induction coil surrounds the outer periphery of the tip of the plasma torch, and an argon plasma flame is generated at the tip of the plasma torch by the high frequency current supplied to the induction coil. The sample atoms in the sample aerosol are heated and excited when passing through the plasma flame, and emit light having a wavelength unique to the atomic species. By performing spectroscopic analysis of this luminescence, qualitative and quantitative measurement of elements in the sample is performed.

  FIG. 5 shows a configuration example of a plasma torch, a spray chamber and a nebulizer that are conventionally used. In FIG. 5, the plasma torch A has a coaxial cylindrical triple structure, and a carrier gas pipe 5 through which a carrier gas (argon gas) containing a sample aerosol is passed is located in the inner core, and the surrounding area is argon for plasma. The plasma gas pipe 4 for flowing gas is configured to further surround the coolant gas pipe 3 for flowing argon gas for cooling on the outermost periphery. And the coil 2 which sends a high frequency induction current to the outer end part of the coolant gas pipe 3 is wound 2 to 3 turns. (See Patent Document 1)

  A nebulizer 7 is hermetically inserted in the spray chamber 8 for supplying the sample aerosol to the carrier gas pipe 5 as shown in FIG. 5, and the carrier gas is supplied through the nebulizer 7. The nebulizer 7 is connected to the sample 9 by a thin tube, and the negative pressure generated when the carrier gas is ejected from the tip of the nebulizer 7 causes the sample 9 to be sucked up by the principle of spraying, and is sprayed into the spray chamber 8 as a fine mist. To do. A leveler 14 is provided at the lower portion of the spray chamber 8, and coarse mist droplets in the atomized sample 9 are discharged to the outside through the leveler 14. At the same time, the leveler 14 seals outflow of the carrier gas by the drainage liquid staying in the leveler 14 and further keeps the liquid level of the drainage liquid constant so that the measurement signal fluctuates due to the fluctuation of the liquid level. To prevent.

  At the time of measurement, a high frequency current is supplied to the coil 2, and a high temperature plasma flame 1 is formed at the tip of the plasma torch A. The sample 9 is aerosolized in the spray chamber 8, mixed with the carrier gas, passes through the carrier gas pipe 5 of the plasma torch A, and finally sent to the center of the plasma flame 1. The sample atoms in the aerosol are heated and excited in the plasma flame 1 to emit light. The emitted light is collected by a condensing optical system using a lens or a mirror on an entrance slit of a spectroscope (not shown in FIG. 5) placed on the side of the plasma flame 1.

In addition to the method of observing light emission from the side of the plasma flame 1 as described above, a method of observing light emission from the direction of the central axis of the plasma flame 1 has been widely adopted recently. In this case, two types of arrangements as shown in FIG. 6 are common. In the example of FIG. 6B, the plasma torch A is placed vertically, and the light emission in the axial direction of the plasma flame 1 is spectroscope by the condenser lens 17 via the mirror 22 provided above the plasma flame 1. It is focused on. On the other hand, in the example of FIG. 6A, the plasma torch A is disposed horizontally, and the light emission in the axial direction of the plasma flame 1 is directly condensed on the spectroscope by the condenser lens 17. In addition, a method of switching the lateral observation and the axial observation of the plasma flame with a plurality of mirrors with the same apparatus is also used. (See Patent Document 2)
JP 2001-272349 A JP 2003-344292 A

  The plasma torch A and the spray chamber 8 in the conventional ICP emission analyzer are configured as described above, but this has the following problems.

  As described above, in order to use the conventional plasma torch, it is necessary to arrange a plurality of optical elements. For this reason, fine adjustment of the optical system before measurement is indispensable. In particular, it is important to adjust the maximum emission point of the plasma flame so that it is accurately positioned at the focal point of the condensing optical system. Usually, the measurer fine-tunes the position of the plasma torch before each measurement. . For this reason, a complicated position fine adjustment mechanism is required, which increases the manufacturing cost of the apparatus and makes the adjustment work complicated. In addition, because of the complicated optical system, there is a problem that the measurement light intensity is reduced before reaching the spectroscope.

  Further, due to a large temperature difference and a flow velocity difference between the plasma flame to be ejected and the surrounding argon gas (purge gas), the boundary between the plasma flame and the surrounding air and its vicinity become a strong turbulent state. In a conventional ICP emission spectrometer that observes light emission from the side of the plasma flame or from the direction of travel of the plasma flame, the accuracy of the measurement signal is increased due to the disturbance that the measured light undergoes when passing through the turbulent flow region. Noise to reduce may be mixed.

  Further, in the conventional ICP emission spectrometer, the plasma torch A, the spray chamber 8 and the leveler 14 are separately provided and connected to each other by a piping system of an appropriate material and shape. It occupies a large volume and becomes an obstacle to downsizing of the entire apparatus. In addition, since the flow path of the aerosol from the spray chamber 8 to the plasma flame 1 is relatively long, the aerosol may be recondensed in the connecting portion of the plasma torch A and the spray chamber 8 or inside the plasma torch A. In the case where the droplets generated in step 1 disturb the flow of the carrier gas or in an extreme case, there is a risk of clogging the flow path of the carrier gas. In particular, as shown in FIG. 6A, when the plasma torch A is arranged horizontally, it is difficult for the droplets generated by the recondensation to be discharged from the leveler 14, and thus the above danger is further increased. Become.

  The present invention has been made in view of the above problems, and does not require a complicated optical system. Therefore, a complicated adjustment mechanism and adjustment work are unnecessary, and the influence of turbulent flow around the plasma flame is reduced. In addition, an object of the present invention is to provide an ICP emission analysis apparatus in which a plasma torch and a spray chamber are efficiently fused and integrated.

  In order to achieve the above object, in the ICP emission spectrometer of the present invention, the plasma torch is a coaxial multi-tube, a plasma flame is formed at one end thereof, and the plasma torch from the other end of the multi-tube plasma torch is formed. An optical system capable of observing the light emission of the plasma flame is provided through the center of. This eliminates the need for fine adjustment work of the optical relative position of the plasma torch or the focusing optical system during measurement, and makes it possible to use the peripheral four sides and the top direction of the plasma flame for other purposes. . Further, the multiple tube of the plasma torch is a coaxial multilayer conical tube, and a spray chamber and a leveler are integrally wrapped therein. Further, the plasma torch includes a conical high-frequency induction current coil wound in parallel with the conical surface of the plasma torch.

  According to the present invention, the fine adjustment work of the optical system before the measurement becomes unnecessary, the number of adjusting mechanisms and optical elements can be reduced, and the apparatus cost can be reduced. Further, by observing the plasma flame from the bottom direction of the plasma torch, noise due to the disturbance of the argon gas (purge gas) around the plasma flame can be reduced. Further, the apparatus can be miniaturized by integrating the spray chamber and the leveler with the plasma torch. Further, the distance from the tip of the nebulizer 7 to the plasma flame 1 is shortened, and aerosolization of aerosol is reduced. Furthermore, high sensitivity can be expected by forming the coil in a conical shape. Further, by opening the periphery of the plasma flame, for example, the ICP emission analyzer and the ICP mass spectrometer can share the plasma flame, and both can be analyzed simultaneously.

  The best mode of the ICP emission analyzer of the present invention is that the plasma torch is a coaxial multi-tube, and a plasma flame is formed at one end of the plasma torch via the center of the plasma torch from the other end of the multi-tube plasma torch. And an optical system capable of observing the light emission of the plasma flame. Further, the plasma torch multi-tube is a coaxial multilayer conical tube, in which a spray chamber and a leveler are integrally wrapped, and a conical high frequency induction current wound in parallel with the conical surface of the plasma torch. A coil is provided, and the entire apparatus is small and compact.

One embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3.
FIG. 1 is an external view when the plasma torch according to the present invention is attached to a spectrometer, FIG. 2 is a view showing a longitudinal section including the central axis of the plasma torch, and FIG. 3 is a cylindrical shape of the plasma torch. It is a figure which shows the cross section which cut | disconnected the base part by the surface perpendicular | vertical to the axial center of a plasma torch. In these drawings, the plasma torch A is configured with a cylindrical base D and a conical portion continuous therewith in appearance. The cylindrical base D is provided with three gas supply ports (a coolant gas inlet 11, a plasma gas inlet 12, and a purge gas inlet 13) for supplying gas to the plasma torch A, which are omitted in the drawing. However, each is connected to a gas flow rate control device of the ICP emission spectrometer by a flexible tube. Further, as will be described later, a spray chamber 8 is provided in the plasma torch A, and a nebulizer 7 for atomizing and supplying the sample to be measured is detachably inserted therein. The carrier gas supply port 24 and the sample introduction port 23 of the nebulizer 7 are also connected to the gas flow rate control unit and the sample container, respectively, by flexible tubes. Moreover, L of FIG. 1 is a leveler, and is attached to the base part D integrally. The discharged liquid from the leveler L is led to a waste liquid tank through an appropriate pipe. The plasma torch A is fixed to the spectroscope B by the fixture 20. However, the shape and the number of the fixtures 20 are not limited to the present embodiment. A coil 2 is disposed near the apex of the conical portion of the plasma torch A. When a high frequency induction current is supplied from the power source of the ICP emission analyzer to the coil 2 and a predetermined flow rate of argon gas is supplied to the plasma torch A, a high temperature plasma flame 1 is generated in front of the conical end of the plasma torch A. .

  As shown in FIG. 2, the plasma torch A is composed of four layers of coaxial conical tubes. The coolant gas is supplied through the coolant gas inlet 11 into the coolant gas pipe 3 of the first layer (outermost layer). A plasma gas is supplied into the plasma gas pipe 4 of the second layer through a plasma gas inlet 12. The carrier gas containing the aerosol of the sample is supplied from the nebulizer 7 to the gap between the third layer carrier gas pipe 5 and the fourth layer purge gas pipe 6 through the cavity of the spray chamber 8. Purge gas is supplied through the purge gas inlet 13 into the purge gas pipe 6 of the fourth layer (innermost layer).

  The plasma torch A is fixed to the spectroscope B by a fixture 20 together with an O-ring 21 for preventing the purge gas from leaking outside or the outside air from entering. Further, the coil 2 is fixed so as to be positioned near the tip of the conical portion of the plasma torch A. In this embodiment, the coil 2 is formed in a conical shape parallel to the conical surface of the plasma torch A. The plasma flame 1 is formed at a position as shown in FIG. When the plasma torch A is fixed to the spectroscope B by the fixture 20, the central axis of the plasma torch A coincides with the optical axis of the condensing optical system of the spectroscope B, and the maximum emission point of the plasma flame 1 is spectroscopic. The plasma torch A, the spectroscope B, and the fixture 20 are designed and processed in advance so as to match the focus of the condenser optical system of the instrument B. In this embodiment, a condensing lens 17 is used as the condensing optical system, and the focal point 18 of the condensing lens 17 matches the maximum light emission position of the plasma flame 1.

  As described above, the spray chamber 8 is provided in the plasma torch A of the present invention. As shown in FIG. 2, the spray chamber 8 is formed in a relatively wide space in which the gap between the carrier gas pipe 5 and the purge gas pipe 6 is expanded at the bottom of the cone, and the nebulizer 7 inserts the tip portion into this space. Has been. The internal structure will be described in detail below with reference to FIG. FIG. 3 is a view of the SS ′ cross section in FIG. 2 as viewed from the bottom of the cone toward the top. The spray chamber 8 is a substantially annular cavity sandwiched between the outer wall of the plasma torch A and the purge gas pipe 6, and a nebulizer 7 is hermetically inserted into the upper portion thereof. A flexible thin tube (not shown in FIG. 3) connected to the sample container is connected to one end (sample introduction port 23) of the central thin tube of the nebulizer 7, and the sample is supplied from this. A carrier gas is supplied from the gas flow rate control unit to the side pipe (carrier gas supply port 24) established in the nebulizer 7. On the other hand, an opening 15 is opened from the spray chamber 8 toward the gap between the purge gas pipe 6 and the carrier gas pipe 5. As shown in FIG. 2, the cavity of the spray chamber 8 passes through the opening 15 and the purge gas pipe 6. And is connected to the plasma flame 1 via the gap between the carrier gas pipe 5.

  The atomized sample is ejected into the spray chamber 8 together with the carrier gas ejected from the tip of the nebulizer 7. A sufficiently fine aerosol is mixed with the carrier gas in the spray chamber 8 and supplied to the plasma flame 1 through the opening 15. Coarse mist droplets and droplets re-aggregated in the spray chamber 8 accumulate at the bottom of the spray chamber 8 as shown in FIG. 3 and are discharged to the outside through the leveler L. The vent hole 10 is opened to maintain the upper surface of the liquid level in the leveler L at atmospheric pressure, and prevents the phenomenon that the discharged liquid suddenly flows out of the leveler L by the siphon principle and causes the liquid level to change suddenly. . In order to prevent the inflow of droplets into the carrier gas pipe 5 from destabilizing the carrier gas flow and consequently causing the plasma flame 1 to become unstable, the opening 15 is connected to the carrier gas pipe 5. As shown in FIG. 3, instead of the entire gap of the purge gas pipe 6, it is limited to a range of an angle θ smaller than 180 ° at the lower part of the gap.

  When the analysis is performed using the ICP emission analyzer according to the present invention configured as described above, four systems of argon gas (coolant) each set to an optimum flow rate by the gas flow rate control unit of the ICP emission analyzer. Gas, plasma gas, carrier gas, and purge gas) are supplied to the plasma torch A, and a high frequency induction current is supplied to the coil 2 from the power supply unit of the ICP emission analyzer, thereby forming a plasma flame 1. The sample is sprayed into the spray chamber 8 through the nebulizer 7 by the action of the carrier gas. The atomized sample becomes an aerosol mixed with a carrier gas in the spray chamber 8 and is sent to the center of the plasma flame 1 by the carrier gas. The element to be measured in the aerosol is excited in the plasma flame 1 by the heat of the plasma flame 1 and emits light. The light emitted from the plasma flame 1 is collected on the spectroscope entrance slit 19 by the condenser lens 17 as shown by the arrow in FIG. Thereafter, the spectroscopic analysis is performed by the functions of the spectroscope B and the photometric unit of the ICP emission analyzer.

  In the above analysis operation, the shape and dimensions of the plasma torch A are fixed to the spectrometer B, the maximum emission point of the plasma flame 1 is on the optical axis of the condensing optical system, and the focal point of the condensing optical system. 18 is guaranteed to match the maximum emission point of the plasma flame 1, so that highly sensitive analysis is possible, and further, the complicated optical system before analysis and the fine adjustment of the position of the plasma torch A are possible. It becomes unnecessary. In addition, a complicated fine adjustment mechanism and an extra optical element such as an extra mirror or lens are not required, so that the manufacturing cost of the apparatus can be reduced, and a decrease in light amount due to the optical element can be minimized.

  In this embodiment, the coil 2 is formed in a conical shape. As a result, the expansion of the plasma flame 1 to the outer edge portion is suppressed, and as a result, the emission intensity distribution is narrowed to the vicinity of the central axis, so that the measurement sensitivity can be expected to improve.

  Further, the inner core portion of the plasma torch A through which light passes is surrounded by the purge gas pipe 6, and since the purge gas flows constantly, there is no mixing of air into the optical path. If the inside of the spectroscope B is evacuated according to a general example, it is possible to perform highly sensitive analysis without loss of light amount due to absorption of oxygen over the entire optical path. Furthermore, since light emission is collected from the bottom of the plasma flame 1 and collected through a gas space in a state close to laminar flow, noise in the photometric signal due to intense turbulence of argon gas (purge gas), which is a problem in the prior art, is reduced. Contamination is minimized.

  Furthermore, the plasma torch A according to the present invention has the spray chamber 8 and the leveler L integrally provided therein. As a result, the entire apparatus can be reduced in size. Further, since the flow path of the carrier gas from the spray chamber 8 to the plasma flame 1 is shorter than that in the prior art shown in FIG. 6, there is a risk that the aerosol is cooled and recondensed in the plasma torch A. Since the cross-sectional area of the carrier gas flow path in the plasma torch A is larger than in the prior art, the risk of droplets generated by recondensation clogging the flow path is also greatly reduced. Yes. In addition, the opening 15 for sending the carrier gas from the spray chamber 8 toward the plasma flame 1 is not provided over the entire circumference of the carrier gas pipe 5 but is opened only in the lower part. As a result, the sample droplet can be prevented from flowing into the carrier gas pipe 5 from the opening 15 to the minimum, and the wall surface of the carrier gas pipe 5 or the purge gas pipe 6 can be opened in the opening 15 even if the liquid droplet flows. In the vicinity of, the inclination is inclined in the direction of the spray chamber 8, so that the risk of droplets flowing out in the direction of the plasma flame 1 is minimized.

  The plasma flame 1 formed by the plasma torch A according to the present invention has an open peripheral area. An example of effectively utilizing this feature is shown in FIG. In this example, the sampling cone 22 of the ICP mass spectrometer C placed side by side is opposed to the plasma flame 1 of the ICP emission analyzer C according to the present invention, and the plasma is supplied from the tip of the plasma flame 1 through the sampling cone 22. The gas ionized by the flame 1 is collected in the ICP mass spectrometer C and analyzed. In the apparatus configured as shown in FIG. 4, both ICP emission analysis and ICP mass spectrometry can be performed with the same apparatus. The features of the present invention are as described above. However, the present invention is not limited to the above and illustrated examples, and includes various modifications. For example, the optical system includes an optical system using a mirror system or an optical fiber without depending on the lens system.

  The present invention relates to ICP (High Frequency Inductively Coupled Plasma) emission analysis.

It is an external view of the ICP emission analysis apparatus of the present invention. It is a longitudinal cross-sectional view of the ICP emission analysis apparatus of this invention. It is sectional drawing (SS 'view of FIG. 2) of a spray chamber. It is a figure which shows the example of the simultaneous measurement by the combination of an ICP emission spectrometer and an ICP mass spectrometer. It is a figure which shows the plasma torch and spray chamber in a prior art. It is a figure which shows arrangement | positioning of the plasma torch and spray chamber in a prior art.

Explanation of symbols

A ... plasma torch B ... spectrometer C ... ICP mass spectrometer 1 ... plasma flame 2 ... coil 3 ... coolant gas pipe 4 ... plasma gas pipe 5 ... carrier gas pipe 6 ... purge gas pipe 7 ... nebulizer 8 ... spray chamber 9 ... sample D ... Base 10 ... Vent 11 ... Coolant gas inlet 12 ... Plasma gas inlet 13 ... Purge gas inlet 14 ... Leveler L ... Leveler 15 ... Opening 17 ... Condensing lens 18 ... Focus 19 ... Spectrometer inlet slit 20 ... Fixed Tool 21 ... O-ring 22 ... Sampling cone 23 ... Sample inlet 24 ... Carrier gas supply port

Claims (3)

To generate plasma flame by a high frequency magnetic field, the sample aerosol is atomized by a nebulizer in the spray chamber, through the flop Razumatochi introduced into the plasma flame, the excitation emission samples atoms in the sample aerosol by the heat of the plasma flame in ICP plasma emission spectrometer for analyzing by, before Kipu Razumatochi consists multiple tube constituted by a conical surface coaxial multilayered, wherein the each of the multiple tube, nebulizer for atomizing a sample, plasma gas, coolant Gas is supplied, purge gas is supplied to the innermost space of the cone, and an optical system is provided for observing the plasma flame formed on the apex side of the cone from the bottom side of the cone through the space inside the cone. , ICP emission spectroscopy, characterized in that a leveler on the bottom side of the cone pipes supplying key Yariagasu Apparatus. The optical system is composed of a focusing optical system, and, ICP emission analyzer according to claim 1, wherein the focus of the focusing optical system is set to the maximum light emission point of the plasma flame.   2. The ICP emission analysis apparatus according to claim 1, wherein a high frequency induction current coil is disposed on a conical surface parallel to the conical surface of the plasma torch.

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