JPH0570097B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a measurement condition adjustment device for a flame atomic absorption spectrometer, a frameless atomic absorption spectrometer, or the like.

(b) Prior art Flame atomic absorption spectrometry involves introducing a sample into a flame, atomizing it, transmitting light from a light source that emits the bright line of the element to be measured through the flame, and absorbing the bright line in the transmitted light. Measure. In addition, in flameless atomic absorption spectrometry, a sample is atomized using a sample atomization reactor such as a carbon cylinder, and the light from a light source that emits the emission line of the element to be measured is passed through the carbon cylinder, and the emission line in the passing light is Measure the absorption of In these analysis methods, a calibration curve is prepared in advance using a standard sample and the sample is quantitatively analyzed, but if the sample solution concentration is too high or the sensitivity of the analytical line (emission line) used is too high, Otherwise, the calibration curve will be curved. This is because in such cases, the absorption of the analysis line by the sample is large, so in areas where the percentage of the measured element in the sample is large, the amount of light incident on the detector is significantly reduced, resulting in stray light unrelated to the sample concentration and self-absorption of the lamp. This is because the influence of If a calibration curve with a large curvature is used, the influence of noise will be greater in the curved and flat portions of the calibration curve. In FIG. 1, the horizontal axis is the concentration, and the vertical axis is the absorbance, and a calibration curve B with a large curvature and a calibration curve L with a small curvature are shown. The difference Δ between the two calibration curves for the same concentration (concentration of the target element in the sample) C means that in the case of B, the apparent absorbance has decreased by Δ due to the influence of stray light or the like. In the portion of the calibration curve B where the curve is flat, a small difference in absorbance causes a large concentration difference, so the influence of noise becomes large.

For this reason, it is necessary to create a calibration curve with as good linearity as possible, and conventionally, a calibration curve with good linearity has been created as follows. The key point of this operation is to reduce stray light, set the sensitivity appropriately low, and stably and appropriately reduce the amount of sample introduced into the sample atomization section. Since there are many things that cause a decrease in the /N ratio, it is difficult to balance the linearity of the calibration curve with the S/N ratio, and the adjustment operation is complicated and time-consuming, and requires considerable skill. It was hot. For this reason, this adjustment was an extremely difficult task for beginners. In order to obtain a calibration curve with good linearity, the adjustment points and direction are as follows: (1) Hollow cathode lamp current value. Lowering this value narrows the width of the emission line spectrum and reduces stray light.

(2) Slit width. Making this narrower will reduce stray light.

(3) Change the analysis line. Among several emission lines, the one with the lowest sensitivity is selected as the analysis line.

(4) Orientation of the burner head that forms the sample atomic transformation flame for flame atomic absorption spectrometry. When tilted relative to the transmitted light flux, the amount of atoms involved in absorption decreases, resulting in lower sensitivity.

(5) Burner head height. Since the concentration of atoms differs depending on the height of the flame, the sensitivity is lowered by shifting it from the highest sensitivity.

(6) Fuel gas flow rate. Shift from maximum sensitivity.

(7) Supplementary gas flow rate. Shift from maximum sensitivity.

(8) The sample is made into a solution, atomized by a nebulizer, and then supplied to the burner.The nebulizer consists of a capillary K that sucks up the sample solution and a nozzle N surrounding it, as shown in Figure 2. Air is sent through the nozzle to suck up the solution and atomize it. When the capillary is moved forward, the suction amount decreases and the sensitivity decreases.

Next, for flameless atomic absorption spectrometry, (9) the amount of sample to be injected into the sample reactor. If you reduce this, the sensitivity will decrease.

(10) Although the furnace temperature is changed over time, lowering the maximum temperature lowers the sensitivity.

(11) Argon gas flow rate in the furnace. Sensitivity decreases as flow rate increases.

There are many adjustment points that can be adjusted like this,
Since each adjustment effect has its own characteristics, some of these adjustment effects must be appropriately combined to achieve the purpose, and adjustment operations require long experience in using the analyzer.

For this reason, the following device configuration has been proposed in the past. For these, a calibration curve is created in advance with a certain setting of the device, and if a sample is measured with the same setting and the absorbance falls within the curved range of the calibration curve, change the device settings and take the measurement again. The configuration is such that an appropriate absorbance range is determined in advance, the sample is measured with one setting of the device, and when the absorbance exceeds the above range, the setting of the device is changed and the measurement is performed again. In both cases, trial measurements are performed on individual samples, and the measurement standards for each sample are different, resulting in inconsistent results when analyzing multiple samples.

(c) Purpose The purpose of the present invention is to automatically change the adjustment operation in order to obtain a calibration curve with good linearity and good balance with the S/N ratio.

(D) Structure The present invention uses an appropriate sample to adjust each adjustment point to an appropriately determined initial state, for example, maximum sensitivity, and using this as a starting point, measures a standard sample to create a calibration curve. Determine whether the curvature of the calibration curve and S/N satisfy predetermined evaluation criteria, and if not, adjust the adjustment points described above by a certain amount in the predetermined direction and create a calibration curve again. To provide an adjustment device that repeats an operation of comparing with an evaluation standard until a calibration curve falls within the evaluation standard. According to this configuration of the present invention, since the equipment has been adjusted so that the calibration curve has less curvature within the concentration range of the standard sample used to create the calibration curve, trial measurement, equipment adjustment, and re-measurement are performed for each sample. There is no need to repeat the above steps.

(E) Embodiment FIG. 3 shows an embodiment in which the present invention is applied to a flame atomic absorption spectrometer. 1 is a hollow cathode lamp that emits the bright line of the element to be measured, 2 is a burner head, F is a flame for sample atomization, 3 is a monochromator, S1 and S2 are an entrance slit and an exit slit, and 4 is a photodetector. , 5 is a signal processing circuit that converts a photodetection signal into an absorbance signal, and 6 is a computer (CPU) that controls the entire device. 8
is the nepurizer, 9 is the fuel supply pipe to Parna 2, 1
0 is also an air supply pipe, 11 is a lamp current control device, 12 is an angular position and vertical position adjustment device around the vertical axis of the burner head, 13 is a nebulizer capillary position adjustment device, 14 and 15 are gas flow rate control devices, 16 is a width adjustment device for slits S1 and S2,
17 is a wavelength driving device for the monochromator 3, and each of these parts is controlled by the CPU 6. The adjustment points are ranked in order, and when determining the conditions for creating a calibration curve, adjustments are made purely from the adjustment point with the highest ranking.

FIG. 4 is a flowchart of the operation of the CPU 6 when creating a calibration curve. When the adjustment operation is started, the adjustment points 11, 12, 1 are first set in the initialization operation (a).
Set 3, 14, 15, 16 to the maximum sensitivity position,
Perform the first calibration curve creation operation (b), then proceed to step
Determine whether or not the calibration curve obtained above falls within the evaluation criteria in (c). If NO, adjust the adjustment point of rank n = 1 by a predetermined amount and in a predetermined direction (d), so that the sensitivity is higher than the standard. If it is below the standard (NO), a warning is given and the operation ends; if YES, 1 is added to n and the operation returns to (B), a calibration curve is created again, and the step is repeated.
After making the determination in (c), adjust the adjustment point of rank n=2 in step (d), and repeat the adjustment operation until the calibration curve etc. falls within the standard unless the sensitivity falls below the standard.

The calibration curve creation operation (b) involves switching the standard sample, importing the absorbance data for each standard sample, calculating each coefficient of the mathematically expressed calibration curve from this data using the least squares method, and storing the calculated coefficients in memory. It's getting more familiar. The concentration range of the standard sample for creating the calibration curve may be adjusted according to the concentration range of the target element to be quantified in the group of samples to be measured. The judgment operation in step (c) is to judge whether the difference between the slope obtained from the two points on the lower end of the obtained calibration curve and the slope obtained from the two points on the upper end of the obtained calibration curve is within the standard.

One adjustment order can include a plurality of adjustment points. The adjustment order can be set freely, and all adjustment points may be adjusted at the same time, but it is common to prioritize the adjustment that has the strongest effect on straightening the calibration curve. Although the initial state is the maximum sensitivity state in the above example, the adjustment position of each adjustment point may be set to the center.

(f) Effect According to the present invention, since the equipment is adjusted so that there is no (small) bend in the calibration curve at the stage of creating the calibration curve, it is possible to With this method, analysis can be performed consistently under the same measurement conditions without having to re-adjust the equipment for each sample, making analysis work more efficient, providing uniform analysis results, and eliminating the need to perform correction calculations on measurement output. Concentration can be determined immediately without any need for data processing, and data processing is simple. Moreover, the conditions of the analyzer are automatically set so that the curvature of the calibration curve falls within the standard without deteriorating the S/N as much as possible, and even a beginner can make adjustments better than an expert.

[Brief explanation of the drawing]

Fig. 1 is a graph of the calibration curve, Fig. 2 is a sectional side view of the main part of the nebulizer, Fig. 3 is a block diagram of an apparatus according to an embodiment of the present invention, and Fig. 4 is a flowchart of the calibration curve creation operation in the same embodiment. It's a chat. 1...Light source, 2...Burner head, S1, S2
... Slit, 8 ... Nebulizer, 9 ... Fuel supply pipe, 10 ... Air supply pipe, 13 ... Capillary adjustment device, 14, 15 ... Flow rate control device.

Claims (1)

[Claims] 1 Set the analyzer to the initial state, measure the standard sample to determine the calibration curve, determine whether the curve of the determined calibration curve is within the standard, determine whether the sensitivity is above the standard,
When the curvature is greater than the standard, adjust the adjustment points of the analyzer in the direction of decreasing the curvature of the calibration curve, create a calibration curve again, and determine whether the curvature is within the standard. A spectroscopic analyzer equipped with a calibration curve creation operation control means that repeats the calibration curve until it falls within the standard.