JPH10142156A - Emission spectrophotometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an emission spectrophotometer by which a spectroscopic analysis can be performed with high sensitivity and with high accuracy by a method wherein light in the part of the central axis of a light-emitting flame is fetched much to the inside of a spectroscope. SOLUTION: A condensing optical system which is composed of a condensing lens 3 and the like is disposed on the extension line of a central axis Fa in such a way that emitted light in the part of the central axis Fa of a light- emitting flame F is condensed with reference to a light-emitting part 1. A light- receiving part 7 at a light guide means 4 which is composed of a bundle of optical fibers 6 is disposed in its condensing position. An optical fiber edge 6a is arranged to be nearly circular in such a way that light is received in a spot shape by the light-receiving part 7, and an optical fiber edge 6b is arranged in a slit shape in such a way that the received light is narrowed down to be a slit shape at a light projection part 8 as the other end part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emission spectrometer for performing elemental analysis by using a luminous flame generated by a sample as a light source and performing elemental analysis, such as an ICP (high frequency inductively coupled plasma) emission spectrometer. More specifically, the present invention relates to an improvement in a portion for guiding light of a luminous flame into a spectroscope.

[0002]

2. Description of the Related Art An ICP emission spectroscopy analyzer converts a sample into plasma and performs spectroscopic analysis using the plasma flame as a light source, and conventionally has a configuration as shown in FIG.

[0003] In FIG. 3, reference numeral 11 denotes a light-emitting portion composed of a plasma torch, and 12 denotes a housing of a spectroscope. The spectroscope in this illustrated example is of the Czerni-Turna type.

In the light emitting section 11, the sample is turned into plasma to generate a plasma flame F. The light of the plasma flame F is transmitted to the entrance slit 14 in the housing 12 by the condenser lens 13.
Light is collected toward. The condensed light is converged in a slit shape by the entrance slit 14, guided to the diffraction grating 16 in parallel via the concave mirror 15, and reflected by the diffraction grating 16 at an angle corresponding to each wavelength. . Then, of the light of each wavelength, light of a specific wavelength is guided to a photodetector 19 such as a photomultiplier through a concave mirror 17 and an exit slit 18, and the light amount is detected by the photodetector 19. Thus, qualitative and quantitative analysis of the elements contained in the sample is performed.

In the wavelength scanning type spectroscope of this embodiment, the diffraction grating 16 is provided with a rotation mechanism 20 for changing the angle thereof, and the exit slit 18 is provided with the rotation mechanism 20 in a direction transverse to the incident light. A moving mechanism 21 for moving is provided.

[0006]

By the way, in the above-mentioned emission spectrometer, the portion for guiding the light of the plasma flame F into the spectroscope is gathered beside the plasma flame F as shown in FIG. With the configuration in which the optical lens 13 and the entrance slit 14 are sequentially arranged, the light of the plasma flame F is guided in a lateral direction substantially orthogonal to the central axis Fa of the flame F.

In this configuration, light emission from each position on the central axis of the plasma flame is focused on each position in the length direction of the slit.

To cope with this, a light condensing system having a configuration as shown in FIG. 5 has recently been used. In this configuration, the condenser lens 13 and the entrance slit 14 are sequentially arranged on an extension of the central axis Fa of the plasma flame F so as to be coaxial with the central axis Fa of the plasma flame F.

In this configuration, since the light of the plasma flame F is led out in the direction along the central axis Fa, the light emitted from the portion along the central axis Fa is taken into the entrance slit 14 side. In the ICP plasma, since the sample passes near the central axis of the plasma flame, the ratio of the light emitted from the sample to the light guided to the spectroscope increases. Therefore, analysis sensitivity can be increased.

[0010] However, the entrance slit 14 on the light condensing side of the plasma flame F is provided to obtain wavelength resolution.
The width Sw is about 20 to 30 μm, and the length Sd is increased to about 4 mm to increase the amount of spectral light. Not only the light emitted from the central axis Fa of the plasma flame F but also the light emitted around the central axis Fa enters through the entrance slit 14, so that unnecessary light is taken in.

The situation will be described in detail with reference to FIG. 6. Light emitted from the central axis Fa of the plasma flame F is focused on the entrance slit 14 by the focusing lens 13, and the focusing position is shown by a thin line in the figure. Thus, it is the center of the total length Sd of the entrance slit 14. As shown by a dotted line, light emission around the central axis Fa is condensed and incident on both sides. The light emission around the central axis Fa has a small rate of light emission of the sample, and such light is incident together with the light emission of the central axis Fa portion, so that the amount of light from the central axis Fa portion where the light emission rate of the sample is large is large. The level decreases relatively.

The flow of the plasma flame F fluctuates non-axisymmetrically in the surrounding area. By taking in the light of the part that changes due to the fluctuation, the influence of the fluctuation of the background light due to the fluctuation on the incident light is obtained. appear.

As described above, in the configuration in which the condenser lens 13 and the entrance slit 14 are arranged coaxially with the central axis Fa of the plasma flame F, of the light emission of each part of the plasma flame F, the light emission of the peripheral portion which is liable to change due to fluctuations. Therefore, sensitivity cannot be sufficiently increased, and high-precision analysis is difficult.

In view of the above conventional problems, the present invention reduces the amount of light emitted around the central axis of the flame of the flame light such as the plasma flame, and efficiently takes in the light of the central axis. It is an object of the present invention to enable high-sensitivity and high-precision spectral analysis.

[0015]

According to the present invention, in order to achieve the above object, a light emitting flame generated by a light emitting section is used as a light source,
In the emission spectrometer, which focuses the light in a slit shape and makes it enter the spectroscope, a light-collecting optical system comprising a bundle of optical fibers and a light-collecting optical system for collecting light generated in a light-emitting portion. And a light guiding means provided from the light condensing position to the entrance slit arrangement position, and the end face of the optical fiber of the light guiding means is arranged in a substantially circular shape on the light receiving side, and is arranged in a slit shape on the light emitting side. Configuration.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings. 1 and 2 relate to an embodiment of the present invention. FIG. 1 is a configuration diagram of an incident portion of light to be subjected to spectral analysis in each portion of an emission spectroscopic analyzer, and FIG. It is a perspective view of a certain light guide means.

In FIG. 1, reference numeral 1 denotes a light emitting portion formed of a plasma torch, and 2 denotes a housing of a spectroscope.

The light emitting section 1 generates a luminous flame from a sample. In this example, the sample is turned into plasma by a high-frequency induction electromagnetic field to generate a plasma flame F. The plasma flame F is a luminous flame that has a high brightness at the central axis Fa and is long along the central axis Fa. The spectroscope is composed of a diffraction grating, a concave mirror, a photodetector, and the like, as shown in FIG. 3. Since the spectroscope does not differ from the conventional example except for the incident portion of the analysis light described later, its configuration is self-evident. The illustration and description are omitted.

The incident portion of the analysis light is formed by the light emitting portion 1 described above,
It comprises a condenser lens 3 as an axially symmetric condenser optical system, and a light guiding means 4. The condenser lens 3 is held by a cylindrical holder 5 attached to the housing 2, and extends the central axis Fa of the plasma flame F so as to be coaxial with the central axis Fa of the plasma flame F in the light emitting unit 1. They are arranged on a line.

The light guiding means 4 is composed of a bundle of optical fibers 6, and has a light receiving portion 7 and a light projecting portion 8 at both ends for fixing the ends of the optical fibers 6 in a predetermined shape. The light receiving portion 7 of the light guiding means 4 has a central axis Fa of the plasma flame F.
Is held by the holder 5 at a position that is coaxial with the condenser lens 3 on an extension of the above, and the end surface thereof faces the focal position on the light projection side of the condenser lens 3. In the light receiving section 7, as shown in FIG. 2, the end face 6a of the optical fiber 6 is arranged in a substantially circular shape.

On the other hand, in the light projecting section 8 of the light guiding means 4, the end faces 6b of the optical fibers 6 are arranged in a slit shape. The light projecting unit 8 faces the arrangement position of the entrance slit 9 inside the spectroscope. More specifically, the end face 6b of the optical fiber 6 is arranged to face the opening 9a with its longitudinal direction coinciding with the longitudinal direction of the opening 9a of the entrance slit 9 (see FIG. 2).

Next, the operation of the above configuration will be described. First,
When the sample is turned into plasma by the light emitting unit 1 and the plasma flame F is generated, the light of the plasma flame F is condensed by the condenser lens 3 as light to be spectrally analyzed, and the light inside the spectroscope is passed through the light guiding means 4. Incident on.

In this case, the condenser lens 3 and the light guiding means 4
1 is coaxial with the central axis Fa of the plasma flame F, the light emission of the central axis Fa portion is, as shown by the thin line in FIG. The end face is focused in a spot shape, and the light emission of the central axis Fa portion is focused on the light receiving unit 7. As shown by a dotted line in FIG. 1, the light emission around the central axis Fa focuses on a position deviated from the end face of the light receiving unit 7, and is not condensed on the light receiving unit 7.
In short, the light receiving section 7 of the light guiding means 4 excludes the light emission in the peripheral portion of the plasma flame F and selectively takes in the light emission in the central axis Fa portion.

The light taken in the light receiving section 7 of the light guide means 4 is guided by the optical fiber 6 to a position corresponding to the entrance slit. In the light projecting section 8 of the light guiding means 4, the end faces 6 b of the optical fibers 6 are arranged in a slit shape. It will be incident inside the spectroscope.

Although the optical fiber 6 has the above-described function of deforming the light beam, it may cause a transmission loss of the light amount, which may be a factor of lowering the analysis sensitivity. Is almost negligible.

Inside the spectroscope, the incident light is guided to a diffraction grating via a concave mirror or the like, and is separated into spectrum lights of each wavelength by the diffraction grating. Elemental analysis detected by a photodetector such as a photomultiplier is performed.

[0027]

According to the present invention, light of a luminous flame such as a plasma flame is condensed in a direction along a central axis thereof, and the light is converged in a slit shape by a light guiding means comprising a bundle of optical fibers. Since it is made to enter the inside of the spectroscope, the luminescence of the central axis portion of the luminous flame is taken in, so that the luminescence of the central axis portion containing a large amount of the luminescence of the sample can be effectively used, and high-sensitivity spectral analysis can be performed. .

In this case, only the emission of the central axis portion of the luminous flame is efficiently taken in, and the ratio of taking in the luminescence around the central axis is small. Therefore, the level of the background light is kept low and the flow around the flame is reduced. The influence of the fluctuation of the background light due to the non-axisymmetric fluctuation can be eliminated, thereby improving the analysis accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an incident portion of an analysis light of an emission spectrometer according to an embodiment of the present invention.

FIG. 2 is a perspective view of a light guide unit that is a part of the above-described part.

FIG. 3 is a configuration diagram of a conventional emission spectrometer.

FIG. 4 is a perspective view of an incident portion of the analysis light of the conventional example.

FIG. 5 is a perspective view of an incident portion of an analysis light according to another conventional example.

FIG. 6 is an operation explanatory view of the other conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light-emitting part, 2 ... Spectroscope housing, 3 ... Condensing lens (axially symmetric condensing optical system), 4 ... Light guide means, 6 ...
Optical fiber, 7: light receiving section, 8: light emitting section, F: plasma flame (luminous flame), Fa: central axis.

Claims (1)

[Claims] 1. A light emitting flame generated by a light emitting unit is used as a light source,
What is claimed is: 1. A light-emission spectroscopic analyzer configured to converge a light generated in a light-emitting part, and a light-condensing optical system, comprising: a light-condensing optical system; Light guide means provided from the light condensing position of the optical system to the entrance slit arrangement position, and the end face of the optical fiber of the light guide means has a substantially circular shape on the light receiving side and a slit shape on the light projecting side. An emission spectrometer characterized by being arranged.