JP3134703U - High frequency inductively coupled plasma mass spectrometer - Google Patents

Abstract

A high-frequency inductively coupled plasma mass spectrometer capable of improving analysis sensitivity is provided.
An injection port for injecting a reaction gas in a flight direction of sample ions in parallel with an ion optical axis is provided around an incident port through which a sample is incident in a reaction cell. The reaction gas injected in the same direction as the flow of the sample serves as a guide in the flight direction of the sample, so that more samples reach the rear stage, so that the analysis sensitivity is improved.
[Selection] Figure 1

Description

  The present invention relates to an inductively coupled plasma-mass spectrometer (ICP-MS).

  ICP-MS is used in a wide range of fields because it is capable of analyzing many elements at the same time and has a feature that high sensitivity analysis is possible. However, as is known, in ICP-MS, molecular ions (called interfering ions) caused by Ar gas used for plasma generation overlap with the peaks of elements having the same mass number and interfere with their spectra. Therefore, there is a problem that the lower limit of quantification of the element to be measured becomes high. For example, when As is measured, if a sample contains a large amount of Cl, a molecular ion in which Ar ions and Cl are combined due to Ar gas is generated. This molecular ion is the same as the As ion. Since it has mass, measurement of As becomes difficult. Examples of such elements that are difficult to measure at low concentrations by ICP-MS include As, Fe, Ca, and Se.

  In the past, various devices and techniques have been developed aimed at solving the above-mentioned problems with interfering ions. One of them is a magnetic field dispersion type ICP-MS, which has a problem that the apparatus is large and expensive. In addition, there is a method of using cold plasma, but this has a problem that a large interference is caused by a matrix of a solvent or an acid.

In recent years, a technique using a reaction cell called a dynamic reaction cell (DRC) has been developed and put into practical use (for example, see Non-Patent Document 1). FIG. 5 shows an ICP-MS apparatus configuration including a dynamic reaction cell.
In an ICP-MS equipped with a dynamic reaction cell, a sample ionized by ICP is first guided to a reaction cell via an interface unit. The reaction cell is supplied with a reaction gas (such as hydrogen) that selectively undergoes a charge transfer reaction with Ar ions, thereby neutralizing Ar ions and removing molecular ions caused by Ar ions from the sample ions. The On the other hand, sample ions are transported behind the reaction cell by the ion guide and discharged from the reaction cell. Among the ions discharged from the reaction cell, ions to be measured are extracted by the MS filter, and the amount of the ions is measured by the detector.

"Inductively Coupled Plasma Mass Spectrometer (ICP-MS)", [online], Nitto Analysis Center, Inc., [February 28, 2007 search], Internet <URL: http://www.natc.co.jp /service/list/icp_ms.html>

  As described above, the dynamic reaction cell has a relatively simple configuration and is low in cost, and can effectively remove interference ions. However, since the ion guide arranged in the dynamic reaction cell actually has only an action of confining the ions, if the sample ions lose the momentum in the axial direction by colliding with the reaction gas, that is, the flight direction of the sample ions. If the is deviated from the ion optical axis, it cannot reach the discharge port of the reaction cell. This caused a decrease in measurement sensitivity.

The high frequency inductively coupled plasma mass spectrometer according to the present invention, which has been made to solve the above-described problems,
In a high frequency inductively coupled plasma mass spectrometer equipped with a reaction cell for removing interfering ions contained in sample ions by reaction with a reaction gas,
In the reaction cell, an injection port for injecting a reaction gas toward the output port in parallel with the ion optical axis is provided around an input port through which sample ions are incident.

  The high-frequency inductively coupled plasma mass spectrometer according to the present invention preferably further comprises a discharge port for discharging the reaction gas from the reaction cell around the emission port in the reaction cell. good.

  In the high frequency inductively coupled plasma mass spectrometer according to the present invention, the reaction gas flows in the same direction as the sample ions and around the axis (that is, the ion optical axis) on which the sample ions ideally fly. By forming the flow of the reaction gas in this way, the reaction gas forms the ion optical axis even when the flight direction deviates from the ion optical axis due to collision of the sample ions with the reaction gas in the reaction cell. As a result, the flight direction of the sample ions is corrected, and the sample ions again fly along the ion optical axis. Therefore, since more sample ions than before are sent to the subsequent stage of the reaction cell, the measurement sensitivity is improved as a result.

  In addition, by providing an outlet for exhausting the reaction gas from the reaction cell around the exit of the reaction cell in the reaction cell, the flow of the reaction gas is further stabilized in the reaction cell. Improvement is realized.

  Hereinafter, embodiments of a high-frequency inductively coupled plasma mass spectrometer according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a reaction cell included in a high frequency inductively coupled plasma mass spectrometer according to an embodiment of the present invention. The reaction cell 1 includes an entrance 2 (indicated by a dotted ellipse) through which sample ions enter and an exit 5 (indicated by a dotted ellipse) from which sample ions exit. Usually, the reaction gas is filled in the reaction cell 1 at a predetermined pressure. An ion guide 4 is also provided inside the reaction cell 1.

  An injection port 3 is provided around the incident port 2 of the reaction cell 1. A reaction gas 6 is supplied to the injection port 3 from the outside of the reaction cell 1 (not shown), and the reaction gas 6 is injected in the direction of the emission port 5 in parallel with the ion optical axis C. The speed of the reaction gas 6 injected from the injection port 3 is preferably supersonic. The structure and shape of the injection port 3 are not particularly limited, but the injection port 3 may be configured so that the flow of the injected reaction gas 6 surrounds the periphery of the ion optical axis C in the axial direction. For example, as shown in FIG. 2, which is a perspective view of the reaction cell 1, the injection port 3 may be formed so as to border the entire entrance port 2. In FIG. 2, arrows representing the reaction gas 6 injected from the injection port 3 are drawn separately, but in reality, the reaction gas 6 injected from the injection port 3 is uniformly around the ion optical axis C. Form a simple flow. The reaction gas 6 that has flew to the vicinity of the emission port 5 is discharged from the reaction cell 1 through a discharge port 7 (not shown in FIG. 2) provided around the emission port 5.

  FIG. 3 is an enlarged view showing an example of the injection port 3. As shown in FIG. 3, the wall near the entrance 2 of the reaction cell 1 has a double structure to form a gap. By supplying the reaction gas 6 from the outside to the inside of the reaction cell 1 at a predetermined pressure, the reaction gas 6 is ejected from the gap at a constant speed. Thereby, the injection port 3 can be formed easily.

  It is desirable that the reaction gas 6 injected from the injection port 3 flies completely in parallel with the ion optical axis C until reaching the emission port 5, but the reaction gas 6 diffuses in the reaction cell 1 during the flight, and the sample Since the path | route (ion optical axis C) where the ion S flies may be obstructed, it is not desirable. In order to avoid this problem, the ejection direction of the reaction gas 6 ejected from the ejection port 3 may be directed slightly outside the ion optical axis C. That is, in the present invention, “rejecting the reaction gas parallel to the ion optical axis” means that the flow of the reaction gas 6 in the reaction cell 1 is parallel to the ion optical axis.

  Another embodiment of the high frequency inductively coupled plasma mass spectrometer according to the present invention is shown in FIG. In the present embodiment, as shown in FIG. 4, the reaction cell 1 is cut in the middle of the high frequency inductively coupled plasma mass spectrometer, and a Q array converging lens 10 and an MS filter are provided at the subsequent stage of the reaction cell. Is provided. In the present embodiment, by appropriately adjusting the direction of the reaction gas 6 injected from the injection port 3, the reaction gas 6 is discharged to the outside of the Q array focusing lens 10, so there is no need to provide a discharge port. There are benefits. Sample ions are collected by the Q array focusing lens and transported to the MS filter at the subsequent stage. In this embodiment, an ion funnel or a DC lens can be used instead of the Q array converging lens.

  As described above, the high-frequency inductively coupled plasma mass spectrometer according to the present invention has been described, but it is clear that the above is only an example, and modifications and improvements may be made as appropriate within the spirit of the present invention. It is clear.

The block diagram of the reaction cell contained in the high frequency inductively coupled plasma mass spectrometer which concerns on one Embodiment of this invention. 1 is a perspective view of a reaction cell included in a high frequency inductively coupled plasma mass spectrometer according to an embodiment of the present invention. An example of the injection nozzle provided in a reaction cell. The block diagram of the reaction cell contained in the high frequency inductively coupled plasma mass spectrometer which concerns on other embodiment of this invention. The figure which shows the apparatus structure of ICP-MS provided with the conventional dynamic reaction cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reaction cell 2 ... Incident port 3 ... Injection port 4 ... Ion guide 5 ... Outlet port 6 ... Reaction gas 7 ... Discharge port 10 ... Q array converging lens C ... Ion optical axis S ... Sample ion

Claims (2)

In a high frequency inductively coupled plasma mass spectrometer equipped with a reaction cell for removing interfering ions contained in sample ions by reaction with a reaction gas,
A high-frequency inductively coupled plasma comprising an injection port for injecting a reaction gas in the flight direction of the sample ions in parallel to the ion optical axis around the entrance port where the sample ions are incident in the reaction cell Mass spectrometer.   The high frequency inductively coupled plasma mass spectrometer according to claim 1, further comprising an exhaust port for exhausting the reaction gas from the reaction cell around an emission port in the reaction cell.

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