JP2000057992A - Mass spectrometry device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute analysis by an internal standard method with high accuracy, in a mass spectrometry device for ionizing a sample by irradiating the sample with a pulse laser and for analyzing it. SOLUTION: A laser beam from a laser light source is divided into two beams by a beam splitter, and applied simultaneously toward two sample plates on a sample stand 112. As an unknown sample and a reference standard sample can be placed separately on each sample plate, each sample can be ionized by using a matrix suitable for each sample and by a laser beam having energy suitable for each sample. Ions produced on the two sample plates are focused toward a detector 113 by an ion lens. Hereby, mass spectrometry of both the ions of the unknown sample and the ions of the reference standard sample can be executed under the same conditions. Therefore, an internal standard analysis having high accuracy can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometer for ionizing a sample by irradiating the sample with a laser beam for analysis.

[0002]

2. Description of the Related Art One of such mass spectrometers is a time-of-flight mass spectrometer (TOFMS).
s Spectrometer). In TOFMS, accelerated ions are introduced into a flight space having no electric or magnetic field, and various ions are separated for each mass number (m / z) according to a flight time required to reach a detector. . FIG. 3 is a schematic configuration diagram of a main part of a conventional TOFMS having the simplest configuration. An ion source 21 is disposed on the left and a detection unit 23 is disposed on the right with the mass separation unit 22 interposed therebetween. The sample stage 211 of the ion source 21, the extraction electrode 221 and the end plate 223 of the mass separation unit 22, and the detector 231 of the detection unit 23 are arranged in a straight line along the ion optical axis C. Sample 2
12 is mixed with a matrix (heating aid),
The sample is placed on a sample dish 213 provided in 11. Sample table 2 on which one or more samples 212 are placed on each sample dish 213
Reference numeral 11 denotes a sample tray 213 on which a sample 212 for analysis is placed at a predetermined position.

At the time of measurement, an extremely short pulsed laser beam is generated by a laser light source 241 and is radiated to a predetermined position by a laser optical system 242. The sample 212 is instantaneously heated and ionized through the matrix.
Various ions generated from the sample 212 are extracted in the direction of the extraction electrode 221 by the potential difference Vs between the sample stage 211 and the extraction electrode 221, and after being accelerated, introduced into the flight space 222 having no electric field and magnetic field. . At this time, ions having a smaller mass number are given higher velocities, so that the ions pass through the flight space 222 and reach the detector 231 earlier.

[0004]

In order to determine the mass number of each ion from the flight time of each ion measured by TOFMS, ions having a known mass number are caused to fly under the same conditions, and the flight time is determined. Must be measured and compared. In addition, in order to perform accurate mass spectrometry of each component of the sample, a standard sample having a known content is ionized under the same conditions,
Must fly (internal standard method). However, since the intensity of laser light, especially pulse laser, applied to a sample generally varies with each irradiation, in order to analyze an unknown sample with high accuracy, the unknown sample and a reference standard sample must be mixed and mixed. Must be placed on the same sample dish and heated and ionized simultaneously by one laser beam irradiation.

However, the optimum laser energy for ionizing each sample is generally different. Also, the appropriate matrix differs for each sample, and when they are mixed, the matrix may be altered or decomposed.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a mass spectrometer for ionizing a sample by irradiating a laser beam to perform analysis. An object of the present invention is to provide an apparatus capable of performing analysis by a standard method with high accuracy.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for irradiating a sample in a sample dish on a sample table placed at a predetermined position with laser light to generate ions. In a mass spectrometer for feeding to a mass separation unit, a) an optical splitter disposed between a laser light source and the predetermined position and configured to simultaneously irradiate two sample dishes on a sample stage with laser light emitted from the laser light source. And b) an ion optical system for sending the ions generated in the two sample dishes together to the mass separation unit.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Laser light emitted from a laser light source is split into two by an optical splitter and is simultaneously applied to two sample dishes on a sample stage. The samples placed on both sample dishes are ionized by laser light and sent to the mass separation unit by the ion optical system. In the mass separation section, both samples are mass separated under the same conditions. As described above, in the mass spectrometer according to the present invention, since the two sample dishes are separately irradiated with the pulsed laser, different types of samples can be independently placed on each sample dish without being mixed. it can. Therefore, an optimal matrix can be used for each sample, and each sample can be ionized with high efficiency.

In addition, since each sample is irradiated with laser light simultaneously, the analyzer is suitable for the case where simultaneous ion generation is required, such as TOFMS. However, the present invention can be applied to a mass spectrometer that does not require the simultaneous generation of ions, taking advantage of the above-described independent mounting of the sample.

[0010] In the mass spectrometer having the above configuration, an appropriate filter is placed in the optical path of one or both of the pulsed lasers, and the energy of the pulsed laser irradiating each sample is set to an optimum value, thereby achieving higher accuracy. Analysis becomes possible.

The mass spectrometer according to the present invention can be used, for example, to place an unknown sample to be analyzed on one sample dish and a reference standard sample on the other sample dish. Thus, a matrix suitable for each sample can be used, and ionization can be performed with laser light having an energy suitable for each sample. Therefore, each sample can be ionized most efficiently. in this way,
By using the mass spectrometer according to the present invention, analysis by the internal standard method can be performed with high accuracy.

[0012]

FIG. 1 shows an embodiment in which the present invention is applied to TOFMS.
And FIG. As shown in FIG. 1, TOFM
S includes an analysis tube 11, an optical system unit 12, and a high-voltage power supply unit 1.
3, a control / data processing unit 14 and the like are provided. A space 111 for ions to fly is provided in the analysis tube 11, and a fixing table for fixing a sample table 112 loaded from the outside is provided at one end of the space 111, and a space 111 is provided at the other end. Is provided with a detector 113 for detecting flying ions. An extraction grid electrode 114 for extracting and accelerating ions generated on the sample stage 112 and a focus lens 115 for converging the ions toward the detector 113 are provided in front of the sample stage 112.

The optical system section 12 and the analysis tube 11 will be described in detail with reference to FIG. The optical system unit 12 is provided with a laser oscillator 121 and a beam splitter 122. A laser beam emitted from the laser oscillator 121 is first split into two laser beams La and Lb by the beam splitter 122.
Is divided into The beam splitter 122 is composed of a semi-transmissive mirror, and the laser beam reflected there is directed to a total reflection mirror 123. The laser oscillator 121 is set so that the laser beam La that has passed through the beam splitter 122 irradiates a sample dish at a first predetermined position on a sample table 112 fixed on a fixed table. 1
23 is set so that the other laser beam Lb irradiates the sample dish at the second predetermined position on the sample table 112. A filter 12 is provided in the optical path of both laser beams La and Lb.
4a and 124b and condenser lenses 125a and 125b are provided, respectively. Filters 124a, 124b
Is for adjusting the transmittance of each of the laser beams La and Lb, that is, the energy of the laser beam applied to each sample.

The procedure for analyzing an unknown sample with the TOFMS of this embodiment is as follows. First, the unknown sample Sa is placed on one sample dish of the sample stage 112, and the reference standard sample Sb is placed on the adjacent sample dish. At this time, an optimal matrix can be used for each of the samples Sa and Sb.
The sample table 112 on which both samples Sa and Sb are placed is loaded into the analysis tube 11, and the lid of the sample loading section is closed. When the operator instructs the control / data processing unit 14 to perform an analysis procedure (program) by operating the operation unit (keyboard, mouse, etc.) of the control / data processing unit 14 and presses a measurement start button, the control / data The processing unit 14 starts a series of analysis according to the specified program. First, the on-off valve and the vacuum pump of each part are operated so that the flight space 111 has a predetermined degree of vacuum.

When analyzing the unknown sample, the sample table 112 is placed so that the sample dish of the unknown sample Sa is at the first predetermined position and the sample dish of the standard sample Sb is at the second predetermined position (or vice versa).
To move. Then, a signal is sent to the laser oscillator 121 to generate a pulse laser for an extremely short time. The pulse laser is split into two by a beam splitter, and is irradiated on the unknown sample Sa and the standard sample Sb on each sample dish to heat and ionize each sample. Here, the filter 12 of each optical path
4a and 124b are of a selection type, and the control / data processing unit 14 controls the filters 124a having appropriate transmittances so that the laser beams La and Lb having the optimum energy for ionizing the respective samples Sa and Sb are irradiated. , 124b are selected for each optical path.

The generated ions of each sample are extracted by the extraction electrode 114 and accelerated. Each ion, regardless of which sample was produced in either sample dish, its mass number (m / m
The acceleration is performed under the same conditions according to z), and is sent to the detector 113 by the focus lens 115. Therefore, in the mass spectrum composed of the ions of the unknown sample Sa and the ions of the standard sample Sb, the qualitative and accurate mass analysis of the unknown sample Sa with reference to the standard sample Sb is performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a TOFMS according to an embodiment of the present invention.

FIG. 2 is a detailed configuration diagram of an optical system unit and an analysis tube of the TOFMS according to the embodiment.

FIG. 3 is a laser and ion optical path diagram of a conventional TOFMS.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Analysis tube 111 ... Flight space 112 ... Sample stand 113 ... Detector 114 ... Extraction grid electrode 115 ... Focus lens 12 ... Optical system part 121 ... Laser oscillator 122 ... Beam splitter 123 ... Total reflection mirror 124a, 124b ... Filter 125a, 125b: condenser lens 13: high-voltage power supply unit 14: control / data processing unit La, Lb: laser beam Sa, Sb: sample

Claims (1)

[Claims] 1. A mass spectrometer for irradiating a sample in a sample dish on a sample table placed at a predetermined position with a laser beam to generate ions and sending the ions to a mass separation unit. An optical splitter that is disposed between a predetermined position and simultaneously irradiates laser light emitted from a laser light source to two sample dishes on a sample stage; and b) masses ions generated in the two sample dishes together. A mass spectrometer comprising: an ion optical system for feeding the light to the separation unit.