JPH0320663A - Mass spectrometer - Google Patents

Abstract

PURPOSE:To obtain a large amount of analytical data within a short time by providing a discharge electrode in a thermospray ion source chamber and turning the voltage applied to the discharge electrode ON/OFF at a high speed and performing mass scanning in synchronous relation to the ON/OFF operation of said voltage. CONSTITUTION:The thermospray fine pipe 3 connected to the column of a liquid chromatograph LC is inserted in a thermospray ion source chamber 1 and heated by a heater 4. Ion extruding voltage is applied to the repeller elec trode 5 arranged in the chamber 1 and, further, a skimmer 6 is provided in the chamber 1 in opposed relation to the electrode 5 and an ion is extruded in a mass spectrometric space through the small hole provided to the leading end of the skimmer 6. Next, a control circuit 13 turns a switch Sw ON/OFF and controls a voltage source 12 in synchronous relation to the ON/OFF opera tion and mass scanning is performed once at each time when the switch Sw is turned ON and OFF by a mass analyzing part 8. Herein, when the switch Sw is turned ON, a voltage source 11 is operated to perform discharge in the chamber 1. The output of an ion detector 9 is the measuring output of two kinds of mass spectra and taken in the circuit 13 to be recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application in Industry B) The present invention relates to a thermospray type ion source for a mass spectrometer.

(Prior art) In mass spectrometry, the thermospray method is used as a method to ionize a liquid sample.The thermospray method is a method in which the sample liquid is injected into the ion source chamber through a heated thin tube. The pressure of the sample liquid gradually decreases as it passes through the capillary, so it becomes atomized, further vaporized, and then injected into the ion source chamber.The sample liquid becomes electrically charged as it is atomized inside the capillary, so it forms mist droplets. The ions of the sample molecules are formed by vaporization.These ions are pushed out through the skimmer into the mass spectrometry space by the action of the riser electrode in the ion source chamber.Thermospray ionization is a method like this. The ions that are detected are mainly solvent ions and ions in which solvent ions and sample molecules bond.Therefore, when using this method of ionization, the mass spectrum obtained is similar to that obtained when using the chemical ionization method (CI method). It is similar to a mass spectrum, and the analysis information mainly provides information on the molecular weight of the sample.On the other hand, for gaseous samples, there is the electron impact ionization method (El).
This method collides accelerated electrons with sample gas molecules to fragment and ionize the sample molecules. Many types of fragmented ions are formed from one molecule, and their mass spectra provide insight into the molecular structure. .

In this way, the analytical information obtained as a result of mass spectrometry differs depending on the ionization method of the sample, so it is desirable to perform mass spectrometry using various ionization methods for one sample. There are some ion sources that can switch between the CI method and the El method, but high-speed switching is difficult. Even in the case of ion source devices for the thermospray method of liquid samples, no one has been proposed that can rapidly switch and obtain mass spectra corresponding to the CI method and the El method.

(Problem M to be solved by the invention) As mentioned above, it is necessary to use multiple types of ionization methods in order to obtain more abundant analysis information of a sample, but conventionally, for this purpose, the same sample is subjected to mass spectrometry twice. There was a need. Particularly in the case of an analyzer that combines a chromatograph and a mass spectrometer, the same sample must be passed through the chromatograph twice, making the analysis very time-consuming.

The present invention aims to quickly switch between two types of ionization methods in a thermospray ion source, thereby making it possible to immediately perform mass spectrometry on the chromatograph outflow fraction using the two types of ionization methods.

Means for Solving the Problems〉 A discharge electrode is provided in the thermospray ion source chamber, and the voltage applied to the electrode is turned on and off at high speed, and in synchronization with the on-off. The mass spectrometer was configured to perform mass scanning each time it was turned off.

(Function) When a voltage is applied to the discharge electrode in the thermospray ion source chamber, an air discharge occurs, and accelerated electrons or ions collide with sample molecules or solvent molecules, resulting in collision ionization.

At this time, sample molecules and solvent molecules are fragmented, and various types of fragmented ions similar to those produced by the ET method are produced. Therefore, if such ions are subjected to mass spectrometry, a mass spectrum obtained by the ET method can be obtained. Since the voltage applied to the discharge electrode is turned on and off at high speed, the production of CI ions and the generation of El ions are switched at high speed, and mass scanning is performed in synchronization with the on and off of the voltage applied to the discharge electrode, so the El method. Mass spectra by both the Cl method and the Cl method can be obtained almost simultaneously.

<Example> FIG. 1 shows an example of the present invention. A thermospray ion source chamber 1 is connected to an exhaust system 2. Reference numeral 3 denotes a thin tube for thermospray, which is inserted into the ion source chamber 1, and a heater 4 is arranged around it to heat it. tubule 3
is connected to the outlet side of a liquid chromatograph LC column. Reference numeral 5 denotes a blade electrode placed in the ion source chamber 1, to which an ion extrusion voltage is applied, and a skimmer 6 is provided in the ion source chamber and protrudes inward, facing the blade. Ions are pushed into the mass analysis space through a small hole at the tip. In the mass analysis space, 7 is an ion beam focusing lens, 8 is a quadrupole mass spectrometer, and 9 is an ion beam focusing lens.
is an ion detector. Reference numeral 10 denotes a discharge electrode whose tip protrudes into the ion source chamber and is connected to a voltage source 11. S
w is a switch that turns on and off the operation of this voltage source 11. 12 is a voltage source that generates DC and high-frequency AC voltages to be applied to the quadrupole mass spectrometer 8, and mass scanning can be performed by changing these voltages applied to the quadrupole. . 13 is a control circuit, switch Sw
is turned on and off, and in synchronization with this, the voltage source 12 is controlled to perform mass scanning. Figure 2 is a time chart showing the synchronization relationship between the on/off of switch Sw and mass scanning.
Mass scanning is performed once when the switch Sw is on and when the switch Sw is off. When the switch Sw is on, the voltage source 11 is activated and discharge occurs within the ion source chamber 1.

FIG. 3 shows one peak of a chromatogram obtained by liquid chromatography LC. This chromatogram is obtained, for example, as a total ion detection signal from a mass spectrometer. In the figure, the vertical solid line indicates the timing of mass scanning while discharge is occurring at the electrode 10, and the vertical dotted line indicates the timing of mass scanning when no discharge is occurring. As shown in this figure, the present invention is characterized in that for one outflow component of the chromatograph, mass spectrum data by CI ionization (thermo spray method) and mass spectrum data by El ionization are obtained alternately. The output of the ion detector 9 is the measurement output of the two types of mass spectra described above, and is taken into the control circuit 13 and recorded.

(Effects of the Invention) According to the present invention, a liquid sample can be analyzed in one analysis operation.
Since mass spectra can be obtained using two types of ionization methods, a large amount of analytical information can be obtained in a short period of time, making it efficient.
The sample also has the advantage of requiring only a single amount, and only a small amount is required.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention, FIG. 2 is a time chart of the operation of the embodiment, and FIG. 3 is a diagram showing the timing of operations on a chromatogram. 1... Ion source chamber 2... Exhaust system, 3... Thin tube, 4
...Heater, LC...Liquid chromatograph, 5...
・Repeller electrode, 6... Skimmer, 7... Ion focusing lens, 8... Quadrupole mass spectrometer, 9... Ion detector, 10... Discharge electrode, 11... Voltage source , SW・
...Switch, 12...Voltage source for mass scanning, 13...
・Control circuit.

Claims (1)

[Claims] A discharge electrode is provided in the ion source chamber having a heated thin tube for a thermospray ion source, and a means for rapidly turning on and off the voltage applied to the electrode is provided, and in synchronization with the turning on and off of the voltage, the voltage is turned on and off, respectively. A mass spectrometer designed to perform mass scanning.