JPH07128227A - Atomic absorption spectrophotometer with sample concentration function - Google Patents

Abstract

(57) [Summary] [Purpose] If the concentration of the element to be analyzed in the unknown sample is lower than the lower limit of quantification, it is automatically concentrated to enable remeasurement. [Constitution] When the absorbance A of the sample is smaller than the lower limit of quantification Astd, the concentration controller 18 determines that the injection controller 10
The sample is repeatedly injected by a fixed amount y by a plurality of times, and each injection sample except the last injection of the repetition is heated in the concentration mode Prog.B by the power supply control unit 12, and the final injection of the repetition is performed. Analysis mode for injected samples
Heat with Prog.M. The concentration calculating unit 20 corrects the concentration calculated from the calibration curve using the measured absorbance A ′ of the concentrated sample by the concentration rate and outputs the corrected concentration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atomic absorption spectrophotometer for quantitatively analyzing metallic elements contained in various substances, and in particular, it is equipped with a flameless atomization unit and equipped with an autosampler for automatic analysis. The present invention relates to an atomic absorption spectrophotometer designed to be used.

[0002]

2. Description of the Related Art In a flameless atomic absorption spectrophotometer, a sample is placed in an electric heating furnace and heated to a high temperature to dry, ash and atomize the sample to generate atomic vapor. Atomic absorption analysis is performed by transmitting light of an appropriate wavelength through the atomic vapor. In the heating furnace, heat is generated by energizing the graphite tube from electrodes on both ends of the graphite tube.

The concentration of the element to be measured in the sample is calculated based on the absorbance obtained from the detection signal from the detector. In order to calculate the concentration from the absorbance, a standard curve showing the relationship between the concentration and the absorbance is prepared in advance using a standard sample of the same amount as the measurement sample amount. A graphite furnace is mainly used as an electric heating furnace in the atomization section, and automatic analysis is performed using an autosampler that automatically injects a sample into the graphite furnace.

In the automatic analysis, when the absorbance of an unknown sample is measured and the absorbance becomes a value larger than the calibration point of the maximum concentration at which the concentration can be calculated from the calibration curve,
Samples are automatically diluted with an autosampler using a diluent, and remeasurement is performed. On the other hand, when the absorbance of the unknown sample is smaller than the calibration point (hereinafter referred to as the lower limit of quantification) of the minimum concentration at which the concentration can be obtained from the calibration curve, the unknown sample is not remeasured.

[0005]

If the concentration of the element to be measured in the sample is not 0, but it is smaller than the lower limit of quantification, re-measurement is not performed and the concentration is calculated by external calibration or the like. Therefore, there is a problem in that the measurement accuracy of a sample having a concentration lower than the lower limit of quantification is deteriorated. When re-measuring such a low-concentration sample, the operator needs to manually concentrate the sample. If concentration is performed manually and re-measurement is performed, a measurement error becomes large and individual differences among workers occur. It is an object of the present invention to automatically concentrate and re-measure when the concentration of an element to be analyzed in an unknown sample is lower than the lower limit of quantification.

[0006]

A flameless atomic absorption spectrophotometer to which the present invention is directed is an electric heating furnace for generating an atomic vapor by heating, energizing, and drying, ashing, and atomizing a sample to be analyzed. And an automatic sampler that automatically injects a sample into an electric heating furnace, an optical system that irradiates atomic vapor in the electric heating furnace with measurement light, and obtains the absorbance of the element to be analyzed from the transmitted light, sample injection and analysis A control device that controls the operation and calculates and outputs the concentration C of the element to be analyzed in the sample from the obtained absorbance A.

The function of the controller is shown in FIG. Control device 8
Is a heating mode that controls the injection control unit 10 that controls the sample injection operation of a predetermined amount x or y by the autosampler 4 and the heating power source 2 of the electric heating furnace. In addition to the analysis mode Prog.M having a process, the power supply controller 12 has a concentration mode Prog.B having a heating process only for drying or a heating process only for drying and ashing.
And a calibration curve storage unit 14 that stores calibration curve data C = f (A) obtained by measuring a standard sample of a fixed amount x,
A comparison unit 16 for comparing the absorbance A obtained by the optical system with the lower limit of quantification Astd when measuring a certain amount x of an unknown sample, and a comparison unit 1.
As a result of comparison in 6, the absorbance A of the sample is the lower limit of quantification Ast.
When it is smaller than d, the injection control unit 10 repeatedly injects a fixed amount y by a plurality of times, and the power supply control unit 12 causes each injection sample except the last injection of the repetition to be concentrated. As a result of comparison between the concentration control unit 18 that causes heating in Prog.B and the heating in the analysis mode Prog.M by the power supply control unit 12 for the last injected sample in the repetition, and the comparison unit 16, When the absorbance A of the sample is greater than or equal to the lower limit of quantification Astd, the concentration is calculated from the calibration curve using the measured absorbance A and output.
When the absorbance A of the sample is smaller than the lower limit of quantification Astd as a result of the comparison in the comparison unit 16, the concentration calculated from the calibration curve using the measured absorbance A ′ of the concentrated sample at that time is corrected by the concentration rate. Concentration output unit 20
It has and.

[0008]

The operation of the present invention will be described with reference to FIGS. First, as analysis conditions, when the concentration of an unknown sample is lower than the lower limit of quantification, the number N of times of concentration in the furnace is set in the concentration control unit 18, and a temperature program for concentration in the furnace Prog.B and a temperature program for measurement in concentration are set. Prog.M is set in the power supply controller 12. A sample injection amount x μl at the time of measuring the standard sample and a normal measurement of the unknown sample and a sample injection amount y μl at the time of concentration in the furnace are set in the injection controller 10. x and y may be equal.
Prior to the measurement of the unknown sample, measurement is performed using a plurality of standard samples with known concentrations of the element to be analyzed, and a calibration curve is created. The calibration curve data is stored in the calibration curve storage unit 14.

Next, an unknown sample is measured as shown in FIG. The autosampler 4 injects x μl of an unknown sample into an electric heating furnace, and the sample is dried, incinerated and atomized in accordance with the measurement temperature program Prog.M, and the absorbance is obtained. If the absorbance is 0 or less, a target element concentration of 0 is output and the measurement ends.

When the absorbance A is equal to or higher than the lower limit of quantification Astd, the concentration calculation unit 20 calculates the concentration by C = f (A) using the calibration curve data in the calibration curve storage unit 14, and the display unit 22 displays the concentration. Displayed and analysis ends.

On the other hand, when the absorbance A is smaller than the lower limit of quantification Astd, the sample is concentrated by the autosampler 4 and remeasured. In the concentration step, the concentration control unit 18 injects y μl of the sample from the autosampler 4 into the electric heating furnace via the sample injection unit 10, and the heating process of only drying or the drying and ashing process via the power supply control unit 12. According to the heating program Prog.B in the concentrating mode including only the heating process, the drying step or the ashing step is performed. After injecting this sample yμl and drying or drying and ashing were repeated (N-1) times, N
At the second time, a yμl sample was injected again from the autosampler 4 into the electric heating furnace, and this time the temperature program for measurement Prog.
According to M, the absorbance is measured through a heating process including drying, ashing and atomization.

The absorbance A'obtained in this way is the absorbance of the concentrated sample. Therefore, in order to convert into the sample amount in x μl when the calibration curve was created, correction by the concentration rate is performed. The corrected density is C = (x / Ny) .f (A '). Here, f (A ′) is the absorbance of the concentrated sample obtained using the calibration curve, and (x / Ny) is the correction coefficient based on the concentration rate.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows a schematic configuration diagram of an embodiment of the present invention. Reference numeral 30 denotes an atomization part, which is provided with a graphite tube that is energized by the heating power source 2 to generate heat. A sample is injected into the graphite tube, and the sample is heated and atomized by the graphite tube. Reference numeral 32 is a light source that irradiates the atomic vapor generated in the atomization unit 30 with measurement light, and for example, a hollow cathode lamp (hollow cathode lamp) is used. Reference numeral 34 is a spectroscope section that disperses the measurement light that has passed through the atomization section 30, and 36 is a detection section that detects the dispersed light. The amplification device 6 amplifies the detection signal of the detection section 36 and calculates the absorbance. To do. The control device 8 includes a CPU and an interface (I / O), performs the functions shown in FIG. 1, and controls the lighting of the light source 32.
The spectroscopic operation in the spectroscope unit 34 is controlled. Reference numeral 38 is an operation unit such as a keyboard.

The heating power source 2 transforms a 200 V AC power source with a transformer 32 and supplies it to the graphite tube in order to control the current flowing through the graphite tube. The energization control is performed by a triac, and the triac is a temperature program Prog.M from the power supply controller 2 of the controller 8.
Alternatively, it is controlled by an ignition pulse signal according to Prog.B.

FIG. 4 shows a schematic plan view of the appearance of one embodiment. Reference numeral 40 is the atomic absorption spectrophotometer main body, and the atomization unit 3
No. 0 graphite tube is provided with a sample injection hole 44 for injecting a sample with an autosampler. A turntable 46 for sample supply is arranged near the atomic absorption spectrophotometer main body 40, and a container 48 is arranged on the turntable 46. The container 48 contains a container containing an unknown sample and a standard sample. , A container containing reagents,
A container containing the blank solution is included. A nozzle washing container and a mixing container are further arranged near the atomic absorption photometer main body 40 and the turntable 46, but they are not shown. For sucking a sample solution such as an unknown sample placed on the turntable 46 and injecting it into the sample injection hole 44 of the graphite tube, mixing the sample in the mixing container, or cleaning the nozzle after the sample injection. In order to move the nozzle to the sample collection position on the turntable 46, the position of the nozzle cleaning container, the position of the mixing container, and the position of the sample injection hole 44, a sampler arm 50 having a nozzle at its tip is arranged. There is.

FIG. 5 shows a suction / discharge mechanism having a turntable 46 and a nozzle 52. The nozzle 52 is provided at the tip of the sampler arm 50, and the sampler arm 50 rotates and moves in the vertical direction. A small capacity syringe 56 having a small capacity is connected to the flow path 52 of the nozzle 52, and a large capacity syringe 60 having a large capacity and a cleaning solution ( Or a blank solution) 62 is connected. The small syringe 56 is used to suck an unknown sample or other sample solution placed on the turntable 46 and inject it into the sample injection hole 44, and the large syringe 60 mixes a plurality of sample solutions with stirring in a mixing container. It is also used for cleaning the nozzle 52 and the mixing container and supplying a blank liquid.

[0017]

In the present invention, when the absorbance of atomic absorption by an unknown sample is smaller than the lower limit of quantification, the unknown sample is automatically concentrated in the furnace and re-measured. Can be increased to an absorbance suitable for obtaining the concentration by using a calibration curve, and the measurement accuracy is improved.
Moreover, the concentration range on the low concentration side that can be quantified is widened by such concentration, and the applicable range is widened. Since the work of concentrating the sample is automatically performed by the autosampler,
There is no human error, and the measurement accuracy is improved in this respect as well.

[Brief description of drawings]

FIG. 1 is a block diagram mainly showing a control device portion in the present invention.

FIG. 2 is a flowchart showing the operation of the present invention.

FIG. 3 is a schematic configuration diagram showing an embodiment.

FIG. 4 is a schematic plan view of one embodiment.

FIG. 5 is a flow path diagram showing a flow path of the autosampler in the same example.

[Explanation of symbols]

 2 heating power source 4 autosampler 6 amplification device 8 control device 10 injection control unit 12 power supply control unit 14 calibration curve storage unit 16 comparison unit 18 concentration control unit 20 concentration calculation unit 22 display unit 30 atomization unit 32 light source unit 34 spectroscopic unit 36 detector

Claims (1)

[Claims] 1. An electric heating furnace for generating an atomic vapor by drying, ashing, and atomizing a sample to be analyzed by heating with electric current, an autosampler for automatically injecting the sample into the electric heating furnace, and an inside of the electric heating furnace. The optical system that irradiates the atomic vapor with the measurement light, determines the absorbance of the element to be analyzed from the transmitted light, controls the sample injection and analysis operation, and calculates the concentration C of the element to be analyzed in the sample from the obtained absorbance A. In a flameless atomic absorption spectrophotometer equipped with a controller that outputs the predetermined amount x or y by an autosampler.
In addition to the analysis mode Prog.M, which has a heating process of drying, ashing and atomization during analysis, as a heating mode for controlling the sample injection operation of the Power control unit with concentration mode Prog.B having only heating process or heating process of only drying and ashing, and calibration curve data C = f (A) obtained by measuring a fixed amount x standard sample The calibration curve storage section, a comparison section for comparing the absorbance A obtained by the optical system with a calibration point Astd of the lowest concentration to which the calibration curve can be applied when measuring a fixed amount x of unknown sample, and a comparison section As a result of the comparison, when the absorbance A of the sample is smaller than the calibration point Astd of the lowest concentration, the injection control unit repeatedly injects the sample a plurality of fixed amounts, and excludes the last injection of the repetition. Power supply for each injected sample The control unit controls heating in the concentration mode Prog.B, and the final injection sample of the repetition is heated in the analysis mode Prog.M by the power supply control unit. As a result, when the absorbance A of the sample is equal to or higher than the calibration point Astd of the lowest concentration, the concentration is calculated and output from the calibration curve using the measured absorbance A, and the result of the comparison in the comparison unit is the absorbance of the sample. A is the lowest calibration point Ast
When it is smaller than d, it is provided with a concentration calculation unit that corrects the concentration calculated from the calibration curve using the measured absorbance A ′ of the concentrated sample at that time and outputs the corrected concentration. Atomic absorption spectrophotometer.