JPS61281943A - Atomic absorption analyzing instrument - Google Patents

Abstract

PURPOSE:To satisfactorily correct background with good S/N and without decreasing atomic absorption sensitivity by energizing only the 1st discharge electrode in the initial period of lighting and further energizing the 2nd discharge electrode in the late period of lighting to generate an atomic cloud. CONSTITUTION:A light source for atomic absorption analysis having a pair of the 1st negative and positive discharge electrodes 20, 21 for radiating the bright line spectra of an analytical element and the 2nd discharge electrodes 23, 24 for generating the atomic cloud 22 of the analytical element on the optical path of the radiated light is used. Only the electrodes 20, 21 are energized in the initial period of lighting and further the electrodes 23, 24 are energized to generate the atomic cloud 22 in the late period of lighting in succession thereof. The emission spectra are thereupon separately sampled in the initial period of lighting and the late period of lighting, by which the absorbancy ratio thereof is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a one-lamp type atomic absorption apparatus that allows for good background correction in atomic absorption spectrometry.

(Prior art and its problems) As a conventional background correction method, for example, there is a method using a hollow force sort lamp (+-I CL ) for measurement and a deuterium lamp for correction. Since the background correction is complicated and the accuracy of the background correction is also problematic, a method as disclosed in Japanese Patent Laid-Open No. 134687/1987 has been proposed as an improvement on this point. . This method can be easily explained as shown in Fig. 5 (Δ).

A conventional HCL in which an anode 2 and a cathode 3 are covered and sealed with an insulator 4 in a glass envelope 1 as shown in (B).
Apply a current as shown in Figure 6 (A>) to generate a self-absorption phenomenon at the peak large current 19, and subtract the absorbance A at the peak n large current ■ from the absorbance A at the normal current 1. In other words, the luminescence profile of the luminescence intensity I at the normal current I. and the luminescence intensity J7 at the peak large current I1 is as shown in Fig. 6 (B). , the absorbance A in each case.,A
, is the atomic absorbance due to the target element in the sample at A3, the background absorbance at A5, and the analytical line center wavelength λ due to the self-absorption phenomenon. If the rate of change in absorbance A due to the decrease in emission intensity at is α (0 × α × 1), then A = A + Ab ... (1)
a A - αA + Ab ... (2) a Since it is expressed as a, the difference An - A between equations (1) and (2)
, -(1-α)Aa·(3), background correction can be performed.

However, the intensity of the light source is very different between normal N current lighting and high current lighting (more than 100 times), and the intensity distribution is also different, resulting in a decrease in S/N (mainly due to the difference in intensity) and This results in uncertain background correction.

Also, the analytical line center wavelength λ due to the self-absorption phenomenon. As shown in Figure 6(B), the luminescence intensity at I
9 Emission intensity during energization", half width of the profile Δλ,
is wide and α is not sufficiently small, resulting in a decrease in atomic absorption sensitivity to J.

Furthermore, depending on the element, the spectral spread of the emitted light during I1 energization may be insufficient, resulting in a decrease in atomic absorption sensitivity.

(Object of the Invention) Therefore, it is an object of the present invention to solve the problems of the prior art described above, and to provide an atomic absorption method which has a good S/N ratio and can perform good background correction without reducing the atomic absorption sensitivity. The purpose is to provide an analytical device.

(Means for Achieving the Object) In order to achieve the above object, an atomic absorption spectrometer according to the present invention includes a first discharge electrode of a pair of yin and yang for emitting bright line spectrum light of an analysis element, A light source for atomic absorption spectrometry is used that has at least one second discharge N electrode for generating an atomic cloud of the analysis element on the optical path, and only the first discharge electrode is energized during the initial stage of lighting, and the lighting continues. In the latter stage, the second discharge electrode is further energized to generate an atomic cloud, and the emission spectra are sampled separately in the early stage of lighting and the latter stage of lighting to obtain their absorbance ratios.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of an atomic absorption spectrometer according to the present invention. In the figure, as the light source 5, a light source unique to the present invention having a first discharge electrode 6 and a second group Ti electrode 7 is used as will be described later. The light source 5 emits bright line spectrum light corresponding to the lighting current 1, 1.2 from the lighting power source 8, and this bright line spectrum light passes through the atomization section 9, undergoes atomic absorption by the analysis element, and is then converted into a spectrometer. introduced in 10. Only the bright line with the highest absorption sensitivity is selected by the spectrometer 10 and converted into an electrical signal by the detector 11. This electrical signal is amplified by the preamplifier 12 and input to the sampling circuit 13.
Then, the sampling pulse S from the pulse generator 14,
The output of the preamplifier 12 is sampled in accordance with SB, and this sampling output is logarithmically converted in absorbance conversion circuits 15 and 16 to convert it into a value proportional to the absorbance. Then, the difference between the converted absorbance values is determined in the subtraction circuit 17, and this is displayed on the display section 18.

FIG. 2 is an explanatory diagram of an NII structure showing an example of a light source for atomic absorption spectrometry used in the present invention. This light source includes, within a glass envelope 19, a pair of first discharge electrodes 20.21 for emitting bright line spectrum light J of the analysis element;
It is constructed by enclosing a pair of negative and negative second discharge electrodes 23 and 24 for generating an atomic cloud 22 of the analysis element on the optical path of the synchrotron radiation J. Each electrode 20.21.23.24
may be covered with an insulator, similar to the conventional HCL shown in FIG.

First discharge electrode 20.21 and second discharge electrode 23.
24 may be arranged at orthogonal positions as shown in FIG. 2(A), or may be arranged coaxially with the direction of the emitted light extraction axis as shown in FIG. 2(B). The point is that the light emitted by the first electrode only needs to pass through the atomic cloud generated by the second electrode. In addition, in the case of the embodiment shown in FIG. 2(B),
Auxiliary cathode 2 serves as the second N pole for generating an atomic cloud.
5, and the anode 21 is shared by the first discharge electrode.

In the embodiment shown in FIG. 2(C), the auxiliary cathode 25 is arranged at a position perpendicular to the first discharge electrode 20.21, and the embodiment shown in FIG. 2(D)
In this embodiment, a U-shaped plate is used as the auxiliary cathode 25 instead of a hollow cylinder. In the above embodiment, the cathode 23. is used to generate an atomic cloud. Since the auxiliary cathode 25 does not need to have a sharp emission line profile, the cathode inner diameter (or interval) d is preferably small to maximize the hollow cathode effect.

FIG. 3 is a timing chart showing the operation of the device of FIG. As the light source 5, for example, the light source shown in FIG. 2(B) is used.
A lighting current [, 12 as shown in FIGS. 3(a) and 3(b) is applied to the auxiliary cathode 25) through the lighting power source 8. That is, in the early stage of lighting (t~1.1-15), only the first group N electrode 6 is energized by the current 11, and in the subsequent late stage of lighting (tz~t3.ts~t6), the first group N electrode 6 is energized by the current 11. 6, the above-mentioned current (1) is continuously applied, and current I2 is also applied to the second discharge MM pole 7, so that an atomic cloud of the analysis element is generated in the latter stage of lighting. The above t1 to t2 may be, for example, several μsec to several tens of μsec, and 11 and I2 may be, for example, several 100 g+8.

At this time, the profile of the light intensity JA of the emitted light from the light source 5 at the initial stage of lighting is the same as the conventional analysis line center wavelength λ, as shown in FIG. However, in the later stages of lighting, it has a sharp peak centered around 1. Second release? H
Since the electrode 5.7 is energized, the profile of the light intensity J8 of the emitted light from the first discharge electrode 5 has a wide half-width as shown in FIG. passes through the atomic cloud of the analysis element generated by the second discharge electrode 7 and undergoes atomic absorption, so the light intensity profile of the emitted light from the light source 5 is analyzed as shown in FIG. 4(B). The intensity at the line center wavelength λ is much weaker than in the vicinity.

At this time, the output V of the preamplifier 12 is as shown in FIG. 3(C), and this output is as shown in FIG. 3(d).

Sampling is performed in the sampling circuit ^ 13 according to the sampling pulses S and SB from the pulse generator 14 shown in (e). That is, the emission spectrum is sampled separately at the early stage of lighting and at the latter stage of lighting. Then, the sampling output 6 at the early stage of lighting and the sampling output VB at the latter stage of lighting are each logarithmically converted into a value proportional to the absorbance in the absorbance conversion circuit 15. The value is displayed on the display section 18.

(Effects of the Invention) As is clear from the above explanation, in this invention, the emission profile of the background absorption correction beam is improved compared to the conventional one, and the light intensity at the center wavelength of the analysis line is extremely weak compared to the vicinity thereof. Therefore, a good background correction effect can be obtained without reducing the light absorption sensitivity.

In addition, since the beams for atomic absorption measurement have high brightness with a narrow emission line width, the S/N ratio is significantly improved (more than one order of magnitude) compared to the method disclosed in JP-A-51-134687. and thus improve detection limits.

Furthermore, compared to the two-lamp method, it is possible to simplify the optical system, make optical adjustment easier, lower the cost of the device, and obtain a better background correction effect while maintaining the same atomic absorption sensitivity. It is excellent in that respect.

In addition, it is superior to the Piman method in terms of simplification of the optical system, operability, equipment cost, atomic absorption sensitivity, and detection limit, and the present invention can produce a double beam effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the atomic absorption spectrometer according to the present invention, FIG. 2 is a structural explanatory diagram showing an example of the light source for atomic absorption spectrometry used in the present invention, and FIG. 3 is the apparatus shown in FIG. 1. Fig. 4 is an explanatory diagram of the light emission profile, Fig. 5 is a structural explanatory diagram showing a conventional hollow cathode lamp, and Fig. 6 shows the lamp current in Fig. 5 and the emission profile at that time. It is an explanatory diagram. 5... Light source, 6... First discharge electrode 7.
...Second discharge electrode, 8...Lighting power source 13...Zumbling circuit 15.16...Absorbance conversion circuit 17...Subtraction circuit 20.21...Yin-yang pair of first discharge electrodes 23 .24
... Yin-yang pair of second discharge electrodes 22 ... atomic cloud,
25... Auxiliary cathode patent applicant Shimadzu Corporation Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) A pair of first discharge electrodes for emitting bright line spectrum light of the analysis element, and at least one second discharge electrode for generating an atomic cloud of the analysis element on the optical path of the synchrotron radiation. Using a light source for atomic absorption spectrometry having a discharge electrode, in the early stage of lighting, only the first discharge electrode is energized, and in the later stage of lighting, the second discharge electrode is further energized to generate an atomic cloud. An atomic absorption spectrometer characterized in that the emission spectra are sampled separately at the early stage of lighting and at the late stage of lighting to obtain their absorbance ratios. (2) The atomic absorption spectrometer according to claim 1, wherein at least one pair of Yin and Yang electrodes, which is separate from the first discharge electrode, is provided as the second discharge electrode. (3) The atomic absorption spectrometer according to claim 1, further comprising at least one auxiliary cathode as the second discharge electrode.