JP2001281223A - Apparatus and method for plasma ion source mass spectrometric analysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma ion source mass spectrometric analyzer by which a sample can be measured safely even when an element to be analyzed and other coexitent elements are contained simultaneously by a method wherein the sample is introduced into the analyzer without a need of confirming a pretreated result by using other analyzer. SOLUTION: In the plasma ion source mass spectrometeric analyzer, the sample in which a plurality of elements are intermingled is ionized by a plasma, and the sample is measured by a mass spectrometer equipped with an ion trap function. The plurality of elements which are designated by a measuring operator are quantitatively analyzed or qualitatively analyzed or semiquantitatively analyzed on the basis of a working curve which is stored in advance. Consequently, a specific element can be quantitatively or qualitatively analyzed ordinarily and semiquatitatively analyzed simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma ion source mass spectrometer for performing elemental analysis by ionizing a sample in plasma.

[0002]

2. Description of the Related Art The measurement of trace metals in environmental water has attracted attention due to the recent frequent occurrence of environmental problems. There is, for example, seawater as an environmental water to be measured. In seawater, a large amount of salt components (Na, Ca, Mg, K, etc.) other than trace metals.
When measuring, the components of these salts must be removed.

Conventionally, when a large amount of elements other than the element to be measured are contained, pretreatment such as flow injection (FIA), solvent extraction, and coprecipitation is performed to obtain a high concentration element in a sample. After performing processes such as removal and concentration of the target element, confirm the results of the pretreatment with an atomic absorption spectrometer or ICP emission spectrometer, and then use inductively coupled plasma (ICP) or microwave induced plasma (MIP). The trace metal element was measured by the plasma ion source mass spectrometer using the TEM.

[0004] This plasma ion source mass spectrometer has an n
The analyzer is capable of performing high-sensitivity measurement on the order of g / L and capable of rapid measurement of multiple elements. However, since the plasma ion source mass spectrometer has high sensitivity and high accuracy, it is not suitable for measurement of high concentration elements.

In particular, when a high concentration of an element (particularly salt) is introduced, the sampling cone is clogged and the detector is deteriorated. Further, the sensitivity is reduced, and the reliability of the data is reduced. Therefore, it is essential to remove (desalinate) high-concentration elements using a pretreatment device such as FIA. It is important that the high-concentration elements be reliably removed by the pretreatment device in order to prevent clogging of the sampling cone, deterioration of the detector, and the like.

[0006]

In the prior art, when a sample to be measured is, for example, seawater, when a metal element having a low concentration of about μg / L or ng / L is measured, a salt of several hundreds of meters is required.
Since it is contained at a concentration as high as about g / L, it has been difficult to directly measure with a plasma ion source mass spectrometer as described above. Therefore, pretreatment such as removal of unnecessary salts and concentration of the element to be measured is indispensable.

Further, in order to ensure the reliability of the pre-treatment, before introducing the pre-treated sample into the plasma ion source mass spectrometer, another analysis device (atomic absorption spectrometer, IC
P components such as Na, Ca, Mg,
K) is measured, and after confirming that pretreatment such as desalination has been performed accurately, it is necessary to perform the work twice, that is, the sample is introduced into a plasma ion source mass spectrometer to measure the target trace metal. Was. Such an operation has a problem that it is complicated, time-consuming, and time-consuming, and there is a danger that the time-consuming operation may increase the number of factors that cause an erroneous operation.

[0008] An object of the present invention is to introduce a sample directly into a plasma ion source mass spectrometer without having to confirm the result of the pretreatment with another analyzer, and simultaneously with the element to be measured, other coexisting elements. It is an object of the present invention to provide a plasma ion source mass spectrometer capable of safely performing a measurement even when the measurement is included.

[0009]

A feature of the present invention to achieve the above object is that a sample in which a plurality of elements are mixed is ionized by plasma and the measurement is performed by a mass spectrometer having an ion trap function. In the source mass spectrometer, quantitative analysis or qualitative analysis or semi-quantitative analysis is performed on each of a plurality of elements specified by a measurer based on a calibration curve stored in advance.

That is, when measuring a sample which is thought to contain an element other than the target element to be measured, a conventional quantitative or qualitative analysis of the target element in the sample is performed, and a non-target element is semi-quantified. The analysis can perform two measurement operations with one sample.

[0011]

Embodiments of the present invention will be described below with reference to the drawings based on embodiments.

FIG. 1 is a block diagram showing the overall configuration of a plasma ion source mass spectrometer to which the present invention is applied.

As shown in FIG. 1, a plasma ion source mass spectrometer according to the present invention mainly includes a sample introduction section 11 for atomizing a sample and a plasma for ionizing a sample introduced from the sample introduction section. Plasma chamber 12 for generating plasma 23, high frequency power supply 1 for generating plasma 23
3, a mass spectrometer 18 for measuring the ionized sample in the plasma chamber 12, control of the entire apparatus and quantitative determination based on the measurement results.
And a data processing device 17 for performing qualitative calculations and the like.

Further, the plasma chamber 12 includes a plasma torch 21 made of quartz and a high-frequency induction coil 22 wound around the outer periphery of the plasma torch 21. )
Is applied. The mass spectrometer 18 includes an ion optical system 14 for efficiently introducing ions into the mass spectrometer, and an ion trap unit 1 for separating ions for each mass number.
5, and an ion detector 16 for detecting a signal extracted from the ion trap 15. FIG. 2 shows the structure of the ion trap section 15. Ion trap part 1
Numeral 5 includes a ring electrode 5 having a hyperboloid of revolution and a pair of end cap electrodes 6 sandwiching the ring electrode 5. By applying a high-frequency voltage and a DC voltage to these electrodes, a three-dimensional quadrupole space is formed, and ions can be confined in this space.

When measurement is performed, ions generated by the plasma 23 are confined in this space, and a high-frequency voltage is applied to each electrode there, and only ions having a certain mass number are confined for a certain time. Specifically, as shown in FIG. 3, a high-frequency voltage having a predetermined amplitude is applied to the ring electrode 5 during the period 31. As a result, ions having a mass number or more corresponding to the applied amplitude are trapped. At the same time, FNF (Filtered Noise) is applied to the end cap electrode 6.
Field) signal is applied to remove ions other than a specific mass number from the three-dimensional quadrupole space. As shown in FIG. 4, the FNF signal is a signal for applying a frequency component other than the natural frequency f ₀ corresponding to the ions to be trapped.

When ions having a specific mass number are trapped during the period 31, the ions applied to the three-dimensional quadrupole space are increased by increasing the amplitude applied to the ring electrode 5 during the period 32. Discharge. By detecting the ejected ions by the ion detector 16, ions having a specific mass number can be measured.

The ion trap section 15 can confine a certain amount of ions having a specific mass number as described above. The amount of confinement, that is, sensitivity, can be adjusted by adjusting the ion confinement time, that is, the period 31 in FIG.

In the present invention, by applying the function of the ion trap section 15, the state of the periods 31 and 32 is repeated and the measurement of a plurality of elements is performed by measuring one sample. In other words, the operation of confining each element and performing measurement, and then confining and performing measurement is repeated. At this time, it is possible to change the confinement time (period 31) for each element to a time suitable for the element concentration.

That is, by measuring the confinement time for high-concentration elements such as Na, Ca, Mg and K in seawater, and increasing the confinement time for trace elements in order to increase the sensitivity, measurement is made possible. Measurement can be performed simultaneously on a sample in which the concentration element and the low concentration element are mixed.

FIG. 1 is a flowchart of the analysis process of the present invention.
It is shown in FIG. Hereinafter, description will be given along a flowchart.

100: Measurement conditions of a plasma ion source mass spectrometer (hereinafter referred to as ICP-MS) are set.
In the setting 100 of the measurement condition, each setting of steps 101 to 105 is performed.

101: First, one of "qualitative analysis" and "quantitative analysis" is selected as a measurement mode of ICP-MS.

102: Next, "matrix element concentration diagnostic measurement" is selected. Here, the matrix element refers to an element contained in addition to the element to be measured. That is, this mode is selected when it is assumed that an element other than the element to be measured may be contained.

When this mode is not selected, ordinary quantitative or qualitative analysis is performed.

103: Set the element to be measured and the matrix element. This setting is performed by displaying the periodic table on the monitor screen of the control unit 17 and selecting from the periodic table.

FIG. 6 shows an example of a setting screen. [Measurement element] 8
If you click on the element name after clicking, the element is recognized as the element to be measured. Similarly, if you click on the [matrix element] 7 and then click on the element name, the selected element is recognized as a matrix element. At this time, the element to be measured and the matrix element are displayed so that they can be distinguished from each other by differentiating display colors and hatching patterns.

Further, a display area 9 indicating the recognized element to be measured and the matrix element is displayed below the periodic table.

104: Set the "ion confinement time" for each element specified in step 103. That is, the period 31 in FIG. 3 is set for each element.

FIG. 7 shows an example of a screen for setting the “ion confinement time”. The setting screen includes a “measurement element setting frame” 10 and a “matrix element setting frame” 11.

The "matrix element" is fixed at "ion confinement time = 10 msec". This is because semi-quantitative determination is performed under certain conditions. The data processing device 17 stores in advance a known calibration curve at an ion confinement time of 10 msec for each element shown in the periodic table. FIG. 5 shows an example of the known calibration curve. FIG. 5A is an example of a known calibration curve of Ag, and FIG. 5B is an example of a known calibration curve of Na.

When a known calibration curve of another ion confinement time is stored, a specific known calibration curve can be selected by the operator. In this case, the ion confinement time indicated in the “matrix element setting frame” 11 is automatically changed to a time corresponding to the known calibration curve selected by the operator.

On the other hand, for the "measuring element", the measurer sets the numerical value of the "measuring element setting frame" 10 for each element. Basically, if the concentration of the element to be measured is low, the confinement time is set long, and if the concentration is considered to be relatively high, the confinement time is set short.

It is possible to simultaneously measure a high-concentration matrix element and a low-concentration measurement element by changing the “ion confinement time” set here.

105: Other various conditions necessary for the measurement are appropriately set.

The above steps 101 to 105 are the condition setting for one sample. If there is another sample to be measured, this condition setting is repeated. Data processing device 17
In, measurement conditions are classified and stored for each sample.

110: When the condition setting is completed, ICP-
The sample is introduced into the MS, and the measurement is performed according to the set conditions.
In the case of the “quantitative measurement” mode, the standard sample measurement and the actual sample measurement are continuously performed as necessary.

120: When the measurement is completed, step 10
One of the analysis processes is performed based on the measurement mode selected in step 1. In the case of the "quantitative measurement" mode, "quantitative analysis of a measurement sample" and "semi-quantitative analysis of matrix elements" are executed.
In the case of the "qualitative measurement" mode, "qualitative analysis of a measurement sample" and "semi-quantitative analysis of matrix elements" are executed.
In the semi-quantitative analysis of the matrix elements, the approximate concentration is calculated based on the known calibration curve corresponding to the ion confinement time stored in the memory of the data processing device 17 in advance.
In the quantitative analysis of the measurement sample in the “quantitative measurement” mode, a calibration curve is separately calculated not by a known calibration curve but by standard sample measurement or internal standard element measurement in an actual sample, and quantification is performed based on the calibration curve.

130: When the analysis process is completed, the result is displayed on the monitor screen of the data processing device 17.

The measurement results (profiles) of the matrix elements and the elements to be measured displayed on the monitor screen are displayed so that they can be easily distinguished. 8 and 9 show examples of the monitor screen.

The display example of FIG. 8 is an example in which the element 12 to be measured and the matrix element display area 13 are represented in separate display areas.

The display example of FIG. 9 is an example in which both profiles are displayed in the same display area. In this case, the differentiation is performed in the form of the profile color or the profile line.

140: Diagnosis of matrix element concentration is performed.

It is determined whether or not the concentration of each matrix element calculated by the semi-quantitative analysis of the analysis processing in step 120 is within a threshold value. The threshold value is stored in the memory of the data processing device 17 in advance similarly to the known calibration curve for semi-quantitative analysis.

The results of the diagnosis are displayed on a monitor together with the approximate density for each rank as shown in FIG. Where C
The rank was an element that could not be detected, the B rank was an element whose presence was confirmed but had a concentration equal to or lower than the threshold, and the A rank had a concentration equal to or higher than the threshold and was judged to be dangerous to continue the measurement. It is distinguished as an element.

In the diagnosis of step 140, if all the matrix element concentrations are below the threshold value (if there is no element of rank A), it is determined that there is no abnormality. Return to 110 and continue the measurement. If there is no sample to be measured, the measurement operation ends.

160; In the diagnosis in step 140, if any matrix element has an element whose threshold is equal to or more than the threshold (A rank), the sample is determined to be abnormal (pre-processing is insufficient), The display warns that a high-concentration matrix element is present, and terminates the measurement operation.

The above is the measurement operation of the ICP-MS of the present invention. In the present invention, when it is considered that an element (matrix element) which is considered to have a bad influence on an apparatus or an analysis result is included in addition to a trace element which is originally intended to be measured, Quantitative and qualitative analysis of matrix elements and semi-quantitative analysis of matrix elements can be performed at the same time.

[0048]

As described above, according to the present invention, semi-quantitative analysis can be performed on a specific element simultaneously with ordinary quantitative and qualitative analysis. This makes it possible to determine whether or not the pretreatment has been sufficiently performed by the plasma ion mass spectrometer.

Further, analysis for confirmation by another analyzer which has been conventionally performed after the pretreatment becomes unnecessary, and a rapid analysis can be performed as an entire analysis process.

In addition, when the pretreatment is insufficient, it is possible to prevent deterioration of the apparatus caused by measurement of a component causing a problem in the apparatus, for example, salt, and lack of data reliability.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration to which the present invention is applied.

FIG. 2 is a structural diagram of an ion trap unit.

FIG. 3 is a diagram showing a high-frequency voltage applied to an ion trap unit.

FIG. 4 is a diagram showing an FNF signal applied to an end cap.

FIG. 5 is a diagram showing an example of a known calibration curve stored in advance.

FIG. 6 is a view showing a setting screen of a measurement element / matrix element.

FIG. 7 is an example of a screen for setting an ion confinement time.

FIG. 8 is an example of a monitor screen showing measurement results.

FIG. 9 is an example of a monitor screen showing measurement results.

FIG. 10 is a diagram showing a diagnosis result of a matrix element.

FIG. 11 is a flowchart showing a measurement sequence according to the present invention.

[Explanation of symbols]

5 end cap electrode, 6 ring electrode, 7 matrix element setting button, 8 measurement element setting button, 1
0… Ion confinement time setting screen “measurement element setting frame”
11: ion confinement time setting screen “matrix element setting frame”, 12: plasma chamber, 13: high-frequency power supply, 14
... Ion optical system, 15 ... Ion trap section, 16 ... Ion detection section, 17 ... Data processing device, 18 ... Mass analysis section,
21: plasma torch, 22: high frequency induction coil, 23
... plasma, 80, 91, 93 ... profile of measurement element, 81, 92 ... profile of matrix element, 94
... Unit of measurement element, 95. Unit of matrix element.

Claims (5)

[Claims] In a plasma ion source mass spectrometer for ionizing a sample in which a plurality of elements are mixed by plasma and performing measurement with a mass spectrometer having an ion trap function, each of a plurality of elements specified by a measurer is specified. , Quantitative analysis or qualitative analysis, or semi-quantitative analysis based on a previously stored calibration curve. 2. The method according to claim 1, wherein a periodic table is displayed for one sample measurement, and an element for performing a quantitative analysis or a qualitative analysis and an element for performing a semi-quantitative analysis are based on the periodic table. A plasma ion source mass spectrometer characterized by specifying each. 3. The mass spectrometer according to claim 2, wherein an ion confinement time is set for each element specified in the periodic table. 4. The plasma ion according to claim 1, wherein the measuring operation is terminated when any of the elements subjected to the semi-quantitative analysis has a measured value equal to or larger than a threshold value stored in advance. Source mass spectrometer. 5. An analysis method using a plasma ion source mass spectrometer for ionizing a sample in which a plurality of elements are mixed by plasma and performing measurement with a mass spectrometer having an ion trap function, wherein a quantitative analysis or a qualitative analysis is performed. A step of designating whether or not to perform semi-quantitative analysis, a step of designating an element for performing quantitative or qualitative analysis, and a step of designating an element for performing semi-quantitative analysis, respectively, Setting a confinement time in an ion trap for each of the following; introducing a sample and measuring; performing quantitative analysis and semi-quantitative analysis, or performing qualitative analysis and semi-quantitative analysis; Ending the measurement operation when there is an element exceeding the threshold value stored in advance as a result. An analysis method using a plasma ion source mass spectrometer.