JPS63122922A - Hollow cathode lamp and atomic absorption/fluorescence spectrophotometer having said lamp as light source - Google Patents

Abstract

PURPOSE:To correct the effect due to a background or scattering with high accuracy, by allowing the light from a post stage hollow cathode lamp. to transmit through the hollow part of a front stage hollow cathode. CONSTITUTION:A hollow cathode lamp (HCL) 1 is equipped with two hollow cathodes composed of the same element, that is, a first post stage hollow cathode C1 and a second front stage hollow cathode C2 and both cathodes C1, C2 are arranged in a vertical row state along the optical axis of the lamp 1 so as to provide a definite distance therebetween. The cathode C2 is a hollow and constituted as a transmission type wherein the light generated from the cathode C1 passes through the hollow part of the cathode 2. Said HCL 1 is used as a light source and a plurality of the hollow cathodes are allowed to light by a large current pulse and the light emitting spectrum line generated by the lighting of the cathode C2 or C1 due to the large current pulse is set to a measuring light source. This light emitting spectrum line is self-reversed by the vapor of the atom generated in large quantities by the lighting of the cathode C2 due to the large current pulse and this self-reversed light emitting spectrum line is used as a background correction light source.

Description

Detailed Description of the Invention The present invention relates to a hollow cathode (HCL) and an atomic absorption/fluorescence spectrophotometer using this lamp as a light source, and particularly relates to an atomic absorption/fluorescence spectrophotometer using a hollow cathode (HCL) and this lamp as a light source. This article concerns a new type of hollow cathode lamp that uses the same lamp as the light source for measurement to provide a light source for correcting background absorption in analysis and scattering in atomic fluorescence analysis, and an atomic absorption/fluorescence spectrophotometer using the same lamp.

In atomic absorption spectrometry, light with a wavelength in the emission line spectrum of the element to be analyzed is incident on the sample atomization section, and the intensity of the transmitted light is measured to determine the amount absorbed by the sample. Quantitative analysis is performed because there is a proportional relationship between the absorption amount and sample concentration, but the sample atomization section has absorption and scattering by various molecular species other than the target element, reducing the accuracy of quantitative analysis. Put it away. This kind of absorption is called background absorption. Conventionally, continuous light sources (
A common method is to measure background absorption using a deuterium lamp (for example, a deuterium lamp) and correct the previously obtained results. There is also a three-wavelength method in which a strong magnetic field is applied to a light source section or an atomization section, and background absorption correction is performed using proximity lines due to Zeeman (Zeen+an) branching of atoms. However, the former requires a separate light source for correction, and the accuracy of correction is not very high. The latter method requires a large-sized device, and because the Zeeman branching method is different, good results cannot necessarily be obtained for all atoms. In contrast, a method has been proposed in which background correction is performed by taking advantage of the fact that when a hollow cathode lamp, which is normally lit with direct current, is driven with a large current pulse, the spectral line width expands.

Although this method is called the S-H method and is a sensible method, some errors may occur if the shape of the spectral line does not completely self-invert when a large current pulse is turned on.

Although atomic fluorescence spectrometry has not yet been established as a general-purpose analysis method, in principle it has greater sensitivity and dynamic range than atomic absorption spectrometry. Lasers, electrodeless discharge lamps, etc. are used as light sources, but
By pulsing a hollow cathode lamp with high current, it has been confirmed that it can be used as an analytical light source. The problem in this case is scattering by the atomic species of the atomized part itself. The problem of scattering correction in atomic fluorescence analysis is similar to the problem of background correction in atomic absorption spectrometry in terms of signal processing, and effective correction means are needed.

Therefore, the purpose of the present invention is to take into consideration the problems of the above-mentioned conventional techniques, and to focus on the S-H method, which does not require a separate light source for correction and does not require a large-scale device. The object of the present invention is to provide a hollow cathode capable of causing complete self-reversal in the shape of spectral lines, and an atomic absorption/fluorescence spectrophotometer using this lamp as both a light source for measurement and correction.

In order to solve the problems of the conventional technology and achieve the above objectives,
In the hollow cathode lamp of the present invention, a plurality of hollow cathodes made of the same element are arranged in a column along the optical axis within the same hollow cathode lamp, and the hollow cathode at the front stage is hollow and the hollow cathode at the rear stage The device is characterized in that it is configured such that the light passes through the hollow part of the front stage hollow cathode.

In addition, the atomic absorption/fluorescence spectrophotometer according to the present invention uses the above-mentioned hollow cathode lamp as a light source, lights the plurality of hollow cathodes with a high current pulse, and generates an emission spectrum caused by the high current pulse lighting of the first or second hollow cathode. This emission spectrum line is used as a measurement light source, and this emission spectrum line is self-inverted by the atomic vapor generated in large quantities by the large current pulse lighting of the hollow cathode in the previous stage, and this self-inverted emission spectrum line is used as a background correction light source for atomic absorption spectrometry. It is characterized by being used as a light source for scattering correction in atomic fluorescence analysis.

The above self-reversal of the emission spectrum line is caused by the atomic vapor generated by the high current pulse lighting of the front hollow cathode and the subsequent hollow cathode being lit by the high current pulse while the atomic vapor generated by the high current pulse lighting of the front hollow cathode remains inside the front and rear hollow cathodes. Preferably, this is produced by time-shared high current pulse lighting of the cathode at predetermined intervals.

Furthermore, self-reversal occurs when the emission spectrum lines generated by the large current pulse lighting of the hollow cathode in the latter stage are absorbed by the remaining atomic vapor, so a transparent shielding plate is installed in the front stage to confine the atomic vapor generated in the hollow cathode in the former stage to a certain space. It is preferable to provide the hollow cathode before and after the hollow cathode.

First, the basic concept of the hollow cathode lamp of the present invention will be explained. Referring to FIG. 1, which shows the principle of atomic absorption spectrometry, monochromatic light generated when a hollow cathode lamp (HCL) 1 is lit with direct current from a drive circuit 2 passes through a frame or frameless atomization section 3. The waves corresponding to the sample are absorbed and become light, which passes through the spectrometer 4 and enters the detector 5. The electrical signal from the detector 5 is processed by the signal processing section 6, and the absorbance of the sample is determined. Now the incident light intensity is Io,
When the transmitted light intensity is I, the absorbance A is determined from the relationship A=log2=a b c ■. Here, a is the extinction coefficient, b is the optical path length, and C is the sample concentration. Quantitative analysis is then performed.

The reason for using HCL as a light source, which has an emission line unique to that element, can be explained with reference to FIG. 2A. The absorption line width of atoms is usually very narrow, on the order of 10<-2 >. therefore,
Using the output light from a normal spectrometer is too wide compared to the absorption line width. In other words, the area of Io becomes large, Io''I, and the absorbance A becomes small.As a result, the linearity of the detection ffivA is no longer maintained.Therefore, the line width as shown in Fig. 2 (A) is ■ A narrow light source is required.

Such HCL is usually used with DC lighting at about 10 to 20 a+A. On the other hand, HCL is repeated at frequency I
KHz, pulse width 20μSec s peak current 200m
When driving with a large current pulse within A, the luminance becomes several 10 to 100 times higher than when DC lighting is applied.
It has been confirmed that the luminance increases by several times to several tens of times when synchronously superimposing the LEDs (approximately 200 Vp-p).

Details regarding such a large current pulse-operated hollow cathode lamp have already been reported by the same author, including the transient emission characteristics of a nearby ion beam and the transient change in spectral line width. (e.g. Spectroscopic Research Dishes, 318 (1983
2 (B) schematically shows how the spectral line width of the resonance line of HCL changes with respect to the current value. (a) is normal DC lighting, (bl is the case when large current pulse lighting is applied, and (C) is the case when the current value is further increased. When the current value is increased, the brightness also increases, but the spectral line width is also expanding.

(Of course, the spectral line width also changes transiently, being narrow after the start of light emission and gradually expanding, but here it is taken as its average value.) In (C), self-inversion occurs.

The main reason for the broadening of the spectral line width is self-absorption by ground state atomic vapor sputtered into the hollow cathode in large quantities by the large current pulse.

The conventional bank ground absorption correction method using the S-H method described above usually involves lighting up the HCL with direct current, as shown in Fig. 3(B) (
Determine the sum of the absorbance due to the sample and the absorbance due to the background in the state shown in a), then turn on a large current pulse at regular intervals to determine the background absorption in the state shown in (b) or (C1), and from the former. The true absorbance is determined by subtracting the latter value.However, with this method, absorption by the sample may occur even in state (A) or state (C), as it is not completely self-reversing. It will be included.

The HCL proposed here consists of (e) and (
The lamp is capable of emitting two types of light having the spectral line shapes shown in d). The background absorption during absorption by the sample can be measured in (d), and only the background absorption can be measured in (e), which is a completely self-inverted version of (d), improving the accuracy of correction.

Isamu Gose Embodiments of the present invention will be described below with reference to FIGS. 3 to 5.

The above-mentioned emission spectrum lines (el and (d) in Fig. 2(C)
), the hollow cathode lamp of the present invention is constructed as shown in FIG.
The lamp includes two hollow cathodes, that is, a first rear stage hollow cathode C1 and a second front stage hollow cathode C2, and both the hollow cathodes C1 and C2 are arranged in a column along the optical axis of the lamp 1 with a certain distance between them. Front stage hollow cathode C
Reference numeral 2 has a hollow shape, and the light emitted from the rear hollow cathode C1 passes through the hollow part of the transmissive type, and the light is taken out in the right direction in the figure as shown by the arrow. Kl and 2 are respective cathodes, and Al and A2 are respective anodes, and the arrangement method, number, and shape of the second anodes can be changed in various ways other than those shown in the drawings. Further, S indicated by a dotted line in the figure is a transparent shielding plate placed before and after the front stage hollow cathode C1 as desired.
It is preferable to provide this because it is effective in confining atomic vapors that contribute to self-inversion of emission spectrum lines.

Next, the operation will be explained with reference to the timing chart of FIG. First, as shown in FIG. 4(a), the low cathode C1 of the rear stage is lit with large current pulses at regular intervals by a pulse signal from an appropriate timing control unit. Among the emission spectrum lines, every other line (1) and (3) shown in FIG. 4(d) are used as they are as a light source for measurement.

On the other hand, when the HCL is turned on with a large current pulse, a large amount of atomic vapor remains within the hollow cathode or before and after the hollow cathode for several hundred microseconds after the end of the light emission.

Therefore, we focused on the fact that during this period self-absorption occurs due to the atomic vapors incident on the resonance line of the same atom, and clean self-reversal can be obtained. Rear stage hollow cathode C1
The remaining every other timing of the light emission timing (
A large current pulse is turned on at a predetermined time (several 100 μsec or less) earlier than 2) and (4). This results in the fourth (C
) As shown in the figure, atomic vapor remains in the front stage hollow cathode C2 and before and after it. Therefore, the latter hollow cathode C1 will be lit with a large current pulse while the atomic vapor remains, and the emission spectrum line will be absorbed by the atomic vapor, and the line (2) in Fig. 4(d) will be emitted from the HCL.
As shown in (4), a completely self-inverted emission spectrum line is obtained, which is used as a light source for background correction. (1), (3) and (2) in Figure 4(d)
).

It is clear that (4) corresponds to (d) and (e) in Figure 3 (C), respectively, and there is no self-reversal that occurs when the hollow cathode in the previous stage is pulse-lit. The emission spectrum lines (5) and (6) can be used as a measurement light source if necessary, or can be ignored depending on the configuration of the signal processing circuit.

Next, FIG. 5 shows an example in which the hollow cathode lamp of the present invention is applied to an atomic absorption spectrophotometer.

As in FIG. 1, the measurement light and correction light from HCL1 are irradiated onto the atomization unit 3, and the light absorbed by the sample or background passes through the spectrometer 4 and enters the detector 5. A timing control unit 7 controls the light emission timing of the HCL 1 and the switching timing of the two-channel boxcar integrators 8 and 9. In other words, the electrical signal from the generator 5 is alternately input to the boxcar integrator 8.9, which is switched in synchronization with the light emission from the subsequent hollow cathode C1. The boxcar integrator 9 integrates the signal containing only the correction background absorption. The signal processing unit 6 calculates the output difference from both boxcar integrators 8.9, and data relating only to sample absorption is obtained. In the illustrated example, a two-channel system is used, but a three-channel boxcar integrator configuration can also be used to subtract the background noise of the detector and signal processing circuit between the background absorption of light and another emission.

In the case of an atomic fluorescence spectrophotometer, the system configuration and operation are similar except that the light detection direction has a certain angle with respect to the excitation light. In addition, it goes without saying that the hollow cathode lamp of the present invention can also be applied to a close two-wavelength light source for -i scientific measurements.

As described above, according to the present invention, completely self-inverted emission spectrum lines can be obtained using a completely new type of hollow cathode lamp, and a back-up light source can be used without the need for a separate light source or large-scale equipment. A light source for atomic absorption/fluorophotometers that can compensate for the effects of ground and scattering with high accuracy can be obtained.

[Brief explanation of the drawing]

Figure 1 is a block diagram to explain the atomic absorption method, Figure 2 is a block diagram to explain the atomic absorption method.
(A) to (B) are diagrams showing emission spectrum lines from a light source and a hollow cathode used for atomic absorption measurement, and FIG. 3 is a perspective view showing the configuration of a hollow cathode lamp according to the present invention.
FIG. 4 is a timing chart for explaining the operation of the hollow cathode lamp, and FIG. 5 is a block diagram showing the configuration of an atomic absorption spectrophotometer to which the present hollow cathode lamp is applied. 1... Hollow cathode lamp, 3... Atomization section, 4
... Spectrometer, 5... Detector, 6... Signal processing section,
7...timing control unit), 8.9...
・Boxcar integrator, C1... Rear stage hollow cathode, C2... Front stage hollow cathode, S... Shielding plate. Applicant: JASCO Corporation Agent
Yukio Maruyama No. 1 Figure =” (C) =” (A) (B) No. 3 6 No. 4 Amendment to Figure Procedures February 18, 1988 Patent Application No. 269039, 1988 2, Title of Invention Hollow Cathode Lang and Atomic Absorption/Fluorescence Spectrophotometer 3 Using the Lamp as a Light Source, Relationship with the Amendment Case Patent Applicant Address: 2967-5 Ishikawa-cho, Hachioji-shi, Tokyo 3-25 Takanawa, Minato-ku, Tokyo No. 27-1208 January 7, 1988 (January 27 of the same year) 6, Specification subject to amendment 7, Contents of amendment (1) Page 15, line 11 of the specification will be amended as follows. 20 is a diagram showing the light source used for atomic absorption measurement of the present invention and emission spectrum lines from the hollow cathode, and Figure 3 is a diagram showing the hollow cathode according to the present invention.''

Claims (4)

[Claims] (1) A plurality of hollow cathodes made of the same element or the same component are arranged in a column along the optical axis within the same hollow cathode lamp, and the hollow cathode at the front stage is hollow and the light from the hollow cathode lamp at the rear stage is hollow. A hollow cathode lamp characterized in that a hollow cathode lamp is configured to transmit through a hollow part of a front stage hollow cathode. (2) Claim 1 characterized in that transparent shielding plates are provided before and after the hollow cathode at the front stage to confine the atomic vapor generated at the hollow cathode at the rear stage in a certain space.
Hollow cathode lamp. (3) A plurality of hollow cathodes made of the same element or the same component are arranged in a column along the optical axis within the same hollow cathode lamp, so that the hollow cathode in the front stage is hollow and the light from the hollow cathode lamp in the rear stage is hollow. Using a hollow cathode lamp configured to transmit light through the hollow part of the hollow cathode at the front stage as a light source, the plurality of hollow cathodes mentioned above are lit with high current pulses, and the emission spectrum lines generated by the high current pulse lighting of the hollow cathodes at the front stage or the rear stage are measured. is used as the measurement light source, and the emission spectrum line from the latter hollow cathode is self-inverted by the atomic vapor generated by the large current pulse lighting of the former hollow cathode, and this self-inverted emission spectrum line is used as the background correction light source for atomic absorption analysis. Or an atomic absorption/fluorescence spectrophotometer characterized in that it is used as a light source for scattering correction in atomic fluorescence analysis. (4) Self-reversal of the emission spectrum line is caused by time-division large current pulse lighting of the hollow cathodes at predetermined intervals at predetermined intervals. Optical spectrophotometer.