JPH0769263B2 - Atomic absorption spectrophotometer - Google Patents

Description

Detailed Description of the Invention a. TECHNICAL FIELD The present invention relates to life control of a graphite tube in a flameless atomic absorption spectrophotometer.

B. Prior Art When using a graphite tube sample atomizer to atomize a sample in flameless atomic absorption spectrometry, the life of the graphite tube becomes a problem. The graphite tube furnace is a furnace that applies a large current to obtain a high temperature, but the electric resistance value increases with repeated use, and after about 500 to 600 times, it deteriorates and the reproducibility of analysis results deteriorates. Cannot be used. The deterioration of the graphite tube can be evaluated by the increase of the electric resistance, and conventionally, the resistance of the graphite tube was measured to judge whether or not the usage limit was reached.

C. Problems to be Solved by the Invention Even if the time for tube replacement is known by the conventional method of measuring the resistance of the graphite tube, it is not known at present how many times it can be used. When actually performing a group of sample analysis, it is necessary to create a calibration curve in advance, but it is desirable that the calibration curve creation and sample analysis be performed under the same analysis conditions. Since it is unclear whether or not it can be used, a situation occurs where the graphite tube must be replaced during the analysis of a group of samples.

The present invention seeks to avoid the above situation by displaying the remaining life of the graphite tube at the present time. The problem for this purpose is that the remaining life of the graphite tube changes depending on the setting of the analysis conditions such as the magnitude of the energizing current and the energizing time, that is, what temperature and how long the graphite tube is kept. However, since the analysis conditions are selected depending on the sample, even if the current resistance of the graphite tube and the final resistance at which the tube should be replaced are known, it cannot be determined how many times the graphite tube can be used.

Therefore, the problem to be solved by the present invention is to obtain an indication of how many times the graphite tube can be used at the present time under the analysis conditions to be performed this time.

D. Means for Solving Problems The value of the intensity of light emitted from the graphite tube at the time of exchanging the graphite tube, that is, the final emission intensity or the final resistance, when the constant current is passed through the graphite tube for a certain time N and the current value. The value and the variation width of the graphite tube emission intensity or resistance per one-time use are stored in the memory in advance, and means for detecting the resistance of the graphite tube or the light emitted from the graphite tube is provided. A calculation display means for calculating and displaying the remaining usable number of times was prepared from the obtained data, the data of the final value stored in advance, and the data of the change width per single use.

E. Action The intensity of the light emitted from the graphite tube when a constant current is applied to the graphite tube for a certain period of time is a function of the number of times the voltage is applied, and if this is P (N), the intensity increases as the number increases, as shown in FIG. . In the figure, Po is the emission intensity indicating the life limit. The lower the applied voltage, the longer the life. If the emission intensity decreases by ΔP with one energization under the standard analysis conditions, the remaining number of uses Nr is calculated from the current emission intensity P and the final emission intensity Po. Required by. ΔP varies depending on the conduction voltage, and even in one analysis, the energization schedule has steps of sample drying, ashing, and atomization, and the voltage increases in steps, so ΔP in one use is the i-th step. The applied voltage of V i, the time of each step is Ti (i = 1,2,3), and the voltage deterioration coefficient is K (Vi)
Then, ΔP = ΣK (Vi) Vi · Ti can be used to obtain the ΔP per run under conditions other than the standard analysis conditions. Therefore, if the analysis conditions, that is, the energization schedule of the graphite tube is determined as Vi and Ti, from the current P,
The remaining number of uses Nr is It is calculated by. Since P (N) and K (V) are experimentally obtained, by storing them in the memory,
It is possible to obtain and display the number of remaining uses under the analysis conditions this time. Instead of the voltage Vi, the degradation coefficient can also be determined for the temperature of the graphite tube or the emission intensity as a function of temperature. The same applies to the resistance value of the graphite tube.

F. EXAMPLE FIG. 1 shows an example of the present invention. L is a light source that emits emission line light of an element to be analyzed, G is a graphite tube of a sample atomization furnace, M is a spectroscope, and the light emitted from the light source L and passing through the graphite tube G is dispersed and dispersed. The light is detected by the photo detector D. A small hole h for obtaining temperature information for controlling the temperature of the graphite tube is formed on the side surface of the graphite tube G,
The light emitted from this small hole is detected by the photocell d. E is a power source for energizing the graphite tube, which is controlled by the controller C. The control device C controls the whole of the atomic absorption photometer,
The output of the photodetector D is acquired, data processing is performed, the result of analysis is displayed on the display means CRT, and the number of remaining uses of the graphite tube G, which is the object of the present invention, is calculated.
It is displayed on the CRT. K is an operation unit where an operator sets analysis conditions and specifies an operation mode of the spectrophotometer. The controller C stores the final light emission intensity Po and the voltage deterioration coefficient K (V) of the graphite tube.

The usage and operation of the above device will be described. When performing analysis, the operator inputs analysis conditions via the operation unit K.
Analytical conditions include the wavelength of the spectroscope and the energization schedule of the graphite tube. Next, when the controller C is instructed to display the remaining number of times of use, the controller C applies a constant current Io to the graphite tube G for a certain period of time, and at this time, a photodetector of light emitted from the small hole h of the graphite tube G. d
The detection signal P (Io) is taken in, the number of remaining uses Nr is calculated by the equation (1) and displayed on the display means CRT.

In the above-described embodiment, the remaining life is detected by the emission intensity of the graphite tube, but since the control device C controls the voltage and current of the graphite tube, it is possible to calculate the resistance of the graphite tube. The number of remaining uses can be calculated from the resistance value when a constant current is applied and the final resistance.

G. Effect According to the present invention, the life expectancy of the graphite tube furnace is found. Therefore, in order to avoid the need to replace the graphite tube during the analysis, make an analysis plan according to the life expectancy or replace the tube in advance. It is possible to operate the device in a rational manner.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention, and FIG. 2 is a graph of a function of the number of times the graphite tube is used and the emission intensity. L ... Light source, G ... Graphite tube, M ... Spectroscope, D
... Photodetector, h ... Small hole, d ... Photodetector, E ... Power supply, C ...
Control device, K ... Operation unit, CRT ... Display device.

Claims (1)

[Claims] 1. An apparatus for observing emission line light emitted from a light source through a graphite tube sample atomization furnace,
A means for detecting the light emitted from the graphite tube or a means for detecting the electric resistance of the graphite tube, and a final luminescence intensity or electric resistance of the graphite tube and the luminescence intensity or electric resistance per single use under specified analysis conditions. The number of remaining usable times of the graphite tube from the means for storing the change width, the difference between the emission intensity or electric resistance of the current graphite tube and the stored emission intensity or electric resistance, and the change width data. An atomic absorption spectrophotometer, which is provided with control means for calculating and displaying.