JPS585632A - Atomic absorption analyzing device for sample - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves directing light from a single light source formed by a spectral line source through a sample to a skewer, generating a magnetic field at the sample or at the location of the light source; Field lines of the magnetic field intersect a light beam directed from the light source through the sample, and the strength of the magnetic field cycles between a maximum value and a zero value at the location of the sample or at the location of the light source. The characteristic resonant spectrum of the element to be searched for in the sample changes alternatingly, causing a periodic Zeeman splitting of the spectral lines generated by the light source and the maximum of the magnetic field in the signal evaluation processing circuit. The present invention relates to a sample atomic absorption analyzer of the type that determines the difference between a detector signal amplitude at a magnetic field strength and a detector signal amplitude at a magnetic field strength of zero.

Atomic absorption spectroscopy is a method for determining the amount of a sought-after element in a specimen or sample. Atoms of an element absorb radiation at wavelengths that are called the resonant spectrum of the element in question.

The wavelength of this resonant spectrum is characteristic for the element in question. In atomic absorption spectroscopy, a light source, such as a hollow cathode lamp, is used to generate resonant spectral lines characteristic of the element being searched for.

A light beam generated by this light source is passed through a sample in which the elements of the sample components are in an atomic state.

For example, a light beam can be passed through a flame into which sample fluid is atomized. The sample can also be atomized "flamelessly" in a graphite tube atomide. The light of the light beam is absorbed by atoms of the element to be searched that have a resonance spectrum corresponding to the spectral lines of the light source, but is not influenced by atoms of other sample components. Therefore, the attenuation of the light beam that passes from the light source through the sample and enters the detector becomes a measure i representing the amount of the element to be searched for in the sample.

However, the absorption of the light beam by the atoms of the element to be searched is often superimposed by unspecified "background absorption or pack-grain P absorption" caused, for example, by light dispersion or molecular absorption.

It is known to compensate for the background absorption by using the Zeeman effect to generate a reference light beam from the same light source that is not affected by the atoms of the element to be searched and receives only the background absorption. Here, the "Zeemann effect" refers to the branching of cis vector lines due to the magnetic field or magnetic field acting on the emitted atoms. In the normal Zeeman effect, the spectral lines are bifurcated or split into three lines by the magnetic field. One of the components remains unshifted in wavelength. This component is called the π component. The other two components, the σ1 component and the O component, are symmetrically (shifted) with respect to the original wavelength and therefore with respect to the π component.

More complex bifurcations occur in the ``abnormal Zeeman effect.'' π
The σ component is polarized linearly in the direction of the magnetic field, while the σ component is polarized perpendicular to the direction of the magnetic field. The strength of all π components is
The total strength is the same as that of the σ component. Conventionally, this effect has been used in various ways to generate a sample light beam and a reference light beam from the same light source in the same optical path.

Conventional device (West German Patent Publication No. 1964469)
In , a magnetic field is applied to the light source 9 such that the field lines of the field are parallel to the axis of the light beam, and the strength of the field varies periodically between its maximum and zero values. is forced to change. The linear Zeeman effect is therefore exploited in a longitudinal magnetic field for the modulation of the emitted spectral lines. When the magnetic field applied to the light source reaches its maximum value, the emitted spectral line is split into two spectral lines, each having a larger wavelength and a smaller wavelength, and the original emitted spectral line disappears. The two spectral lines thus obtained are no longer absorbed by the atoms of the element to be searched for. This is because these spectral lines are shifted relative to the resonant spectrum of the atom.

In this state, the light beam acts as a reference light. When the magnetic field strength reaches a value of zero, the generated spectral lines and the atomic resonance spectrum of the element to be searched coincide. This light beam acts as a sample light beam in the manner described above. This mode of operation therefore requires a magnetic field with magnetic field lines extending parallel to the longitudinal axis of the light beam. It is difficult to generate such a magnetic field with sufficient strength due to the strong force. This is because, in this case, the optical path of the light beam is not interfered with by the magnetic poles of the magnet.A new type of device is known, in which the light source has the axis of the light beam A constant magnetic field with transverse magnetic field lines is applied. With such a constant magnetic field, as already mentioned above, the spectral lines emitted from the light source are split into a π component polarized parallel to the constant magnetic field and a σ component polarized perpendicular to the constant magnetic field. The π component has the wavelength of the original spectral line that would be generated in the absence of a magnetic field. On the other hand, the σ component is shifted to the resonance spectrum of the element to be searched and therefore is not absorbed, and the reference light beam
Can be used by closing.

In order to alternately switch between the sample light beam and the reference light beam, two polarization filters with polarization planes that act periodically and sequentially in time and are oriented perpendicular to each other are connected to the light source and the detector. It can be placed between. Alternatively,
A single rotating polarizer may be provided in the optical path.

Further, from the specification of West German Patent Publication No. 1964469, a light source is a magnetic field having lines of magnetic force in a direction transverse to the axis of the light beam, the strength of which changes periodically between a maximum value and a value of zero. Devices are known that add to the A polarizing filter with a fixed plane of polarization is placed between the light source and the detector. This polarizing filter is arranged so that its plane of polarization is perpendicular to the direction of the lines of magnetic force. Therefore, the π component polarized parallel to the direction of the magnetic field lines is not transmitted, while the σ component polarized perpendicular to the direction of the magnetic field lines is transmitted. Therefore, when a magnetic field is applied, the light beam is shifted in wavelength and has a σ component that is not absorbed by the atoms of the element to be searched. When the magnetic field assumes a value of zero, the undisturbed emitted spectral lines are polarized by a polarizing filter and impinge on the detector as a measuring light beam.

In the two prior art devices mentioned above, a magnetic field transverse to the beam axis is actually used so that the pole pieces of the magnet generating the field do not interfere with the optical path of the light beam. However, it is necessary to provide a polarizing filter in the optical path, and the use of such a polarizing filter not only increases the cost accordingly, but also can interfere with the absorption measurement.

In all the devices mentioned above, a magnetic field acts on the light source to branch or split the spectral lines emitted by the light source by the Zeeman effect.

West German Patent Application Publication No. 21651 [From specification No. 16]
It is known to generate a magnetic field in the region of a specimen or specimen, with magnetic field lines oriented transversely to the light beam. In this device, instead of the spectral lines generated by the light source being split or branched by the Zeeman effect, the resonance spectrum of the element to be searched is subject to Zeeman splitting. When a magnetic field is applied, the sample emits a light component (π component) that is polarized parallel to the direction of the magnetic field and has a wavelength in the resonant spectrum.
and light having a wavelength that is polarized perpendicular to the direction of the magnetic field and shifted to the wavelength of the resonant spectrum (σ component)
absorb. The magnetic field is modulated between zero strength and a maximum value. A fixed polarization filter is arranged in the optical path between the sample and the detector, and the polarization plane of this filter extends perpendicular to the direction of the magnetic field.

When a magnetic field is applied, the resonant spectral lines , π,
The plane of polarization of the light beam that is absorbed by the acid component is not transmitted to the polarizing filter. On the other hand, the transmitted plane of polarization has a different wavelength and is therefore not absorbed by the π component. Therefore, when a magnetic field is applied, the light beam acts as a reference light beam. When the magnetic field reaches zero strength, the components of the resonant spectrum coincide again and the plane of polarized light transmitted or transmitted by the polarizing filter is absorbed by the atoms of the element to be searched for, as usual. In this case, therefore, the light beam acts as a sample light beam.

Furthermore, it is also known to generate a constant magnetic field at the location of the specimen or specimen, with lines of magnetic field oriented transverse to the axis of the light beam, and also to place a rotating polarizing filter in the optical path (see Hitachi's brochure ' What engineering s P
o1arizedZeemanFifect A,
A, S? (see J).

In the case of these conventional devices in which a magnetic field is applied to the area of the specimen or sample, a polarizing filter is also used and is considered an essential element for the operation of the device.

The object of the invention is to simplify the structure or design of a device of the type mentioned at the outset and to obtain an absorption signal that is less susceptible to interference compared to conventional devices.

According to the invention, the above object is achieved by not providing an optical polarizing element in the optical path between the light source and the detector.

.

Surprisingly, it has been found that even when the polarizing filter is omitted, a signal that allows compensation of background absorption can be obtained. By compensating for background absorption in this way, disturbances or disturbances in the measurement, such as those caused by the provision of polarizing filters in conventional devices, are avoided. Furthermore, the structure of the device is considerably simplified by omitting the polarizing filter.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to FIG. 1, a light beam 10 is generated by a spectral line generating light source 12 in the form of a hollow cathode lamp. This light beam 10 passes longitudinally and axially through a graphite tube of a graphite tube atomizer 14, which is schematically shown.

A graphite tube atomide comprises a graphite tube held between two cooled annular electrodes in a well-known manner. The test sample is placed inside a graphite tube. The graphite tube is then intensely heated by the electrodes and the electric current flowing through the graphite tube. As a result, the sample or specimen decomposes and becomes atomized, forming a "cloud of atoms" inside the graphite tube. Within this cloud of atoms, the individual components of the sample or specimen are in an atomic state.

A magnetic field is generated at the location of the song by an electromagnet 16 energized with alternating current. Within the graphite tube atomide 14, the strength of this magnetic field therefore alternates periodically between a maximum value and a zero value.

The light beam 10 emerging from the graphite tube atomizer f14 is directed via a monochromator 8 to a detector 20 in the form of a photomultiplier tube.

The output signal of the detector 20 is fed to a signal processing circuit 22 which generates an atomic absorption signal corrected for background absorption, which signal is recorded by a recording device 24, for example.

In contrast to conventional devices, the optical path of the device disclosed herein is not equipped with a polarizer or polarizing filter.

Next, the operation of the above-described apparatus will be explained with reference to FIGS. 2 and 6. The element to be searched has the same resonant spectrum as the spectral lines produced by light source 12 (indicated by reference numeral 26 in FIG. 2). At this wavelength, the light beam 10 is absorbed by the atoms of the element to be searched within the sample when the magnetic field strength is zero.

This absorption is unpolarized light in this example. This occurs regardless of the polarization plane of the light beam.

When a magnetic field is applied to the sample, the resonance spectrum of the element to be searched becomes a "π component" having the same wavelength as the original resonance spectrum 26.
28 and two elongated components located at the same spacing on either side of the π component, namely a σ component 30 and a σ-component 32. The π component is polarized parallel to the direction of the magnetic field. That is, atoms of the element to be searched at this wavelength absorb only the light component in the light beam 10 that is polarized parallel to the direction of the magnetic field. The σ component is polarized in a direction perpendicular to the direction of the magnetic field. Therefore, at this wavelength, the atoms of the element being searched for are
It absorbs only light that is polarized perpendicular to the direction of the magnetic field.

The effect of the above-described light splitting in the apparatus shown in FIG. 1 will be explained with reference to FIG. 6.

Block 34 shows the situation resulting from a magnetic field of zero strength. In the figure, 36 represents the emission spectrum of the light source 12, which is shown as a single spectral line for convenience of explanation. The absorption profile in the optical path is shown by curve 38.

This absorption profile or spectrum includes a background absorption 40 as well as an absorption band 42 at the wavelength of the spectral line of the emission spectrum 36 due to the resonance spectrum of the atoms of the sampled element to be searched. The plane of polarization is not involved in any way. The amplitude of the detector output signal, as shown in block 40, represents the atomic absorption by the atoms of the element being searched in the sample plus the background absorption.

Block 46 shows the conditions resulting from applying a magnetic field. The emission profile of light source 12 is again shown by curve 36, and the background absorption is represented by curve 40. The absorption profile 48 of the optical path superimposed on the background absorption 40 includes a band 50 corresponding to the π component 28 and a band 5 on both sides thereof corresponding to the σ component.
2 and 54. However, the π component 28 of the resonance spectrum split by the Zeeman effect absorbs only that part of the light beam 10 that is polarized parallel to the direction of the magnetic field.

Since light beam 10 is unpolarized, band 50 has only half the height of band 42.

Light beam 10 is not absorbed by σ components 30 and 32 because its wavelength is not the same as the wavelengths of σ components 30 and 32.

As shown in block 56, the detector signal generated by the applied magnetic field also includes background absorption as well as half of the atomic absorption by the atoms of the element being searched (since only planes of polarization parallel to the magnetic field are absorbed). . The background absorption is then compensated for by forming a difference, as shown at 58.
A signal representing atomic absorption by the atoms of the element to be searched for in the sample is obtained.

The SN ratio is improved by not using a polarizing filter.

The ratio of the background-compensated absorption signal and the corresponding 100% signal, i.e. the background-compensated attenuation of the measuring light beam caused by absorption and the intensity of the beam corresponding to 100% transmission, is therefore reduced by a factor of 0.5. do. This reduction in meaningful signal could be compensated for by corresponding electronic amplification means, since as above the signal-to-noise ratio is improved by not using a polarizing filter.

Similar considerations would apply if a magnetic field were applied at 120 light sources.

[Brief explanation of the drawing]

FIG. 1 schematically illustrates the structure of an atomic absorption spectrophotometer in which the Zeeman effect is utilized to generate a sample light beam and a reference light beam that are generated by the same light source and extend in the same optical path; FIG. 2 is a diagram illustrating the division of the resonance spectrum of the element to be searched by the usual Zeeman effect, and FIG. 6 is a diagram schematically illustrating compensation for background absorption by the sample light beam and the reference light beam. 10... Light beam, 12... Light source, 14... Atomizer, 16... Magnet, 18... Monochromator,
20...Detector, 22...Signal processing circuit, 24...
・Recording device, 26...resonance spectrum, 28...π
component, 30...σ component, 36... emission spectrum,
38...Curve, 40...Background absorption, 42...Absorption band, 48...Absorption profile, 50,52.54.
...bandwidth. - Engraving of the drawings (no change in content) Procedural amendment (method) August 5, 1980 Mr. Commissioner of the Japan Patent Office 1, Indication of the case Patent Application No. 56471 of 1988 2,
Name of the invention Sample Atomic Absorption Analyzer 3, Relationship with the person making the amendment % Applicant Song July 27, 1980 (Shipping date) However, engraving of the drawings (no changes to the contents)

Claims (1)

[Claims] 1. Light from a single light source (12) formed by a spectral line source is passed through a sample (14) to a detector (2).
0), the sample (14) or the light source (12
), and the magnetic field lines of the magnetic field are located at the light source (
a beam of light (10) directed from 12) through the sample (14), and the strength of the magnetic field is at a maximum at the location of the sample (14) or at the location of the light source (12). cyclically alternating between the values of , and the signal evaluation processing circuit (
22), in which the light source (12) and the detection An atomic absorption analyzer for a specimen, characterized in that an optical polarization element is not included in the optical path between the specimen and the specimen.