JPH02176454A - Method for introducing specimen into mass spectrometer - Google Patents

Abstract

PURPOSE:To make it possible to introduce a minute amount of liquid specimen stably by simple operation in a simple device by maintaining a vacuum state in a small chamber which is provided in front of an ionizing chamber, sucking the liquid specimen under atmospheric pressure through a capillary, and ionizing the specimen in the ionizing chamber. CONSTITUTION:A liquid specimen L in a container 7 is slowly sucked through a capillary 3 due to the difference between atmospheric pressure and the pressure in an ionizing chamber 2. The specimen is heated with a heater 5 in halfway. The specimen is evaporated when the specimen enters into the chamber 2. Electrons emitted from a filament hit the vapor, and ionization occurs. Thus, the mass spectrum of the flagment ions is obtained in a mass spectrometer by an EI ionization method. When the inner diameter of the capillary is made to be about several tens of mum, the pressure in the chamber 2 can be kept at about 10<-4>Torr readily. The sucked amount is minute. It is not necessary to compress the solution. The device and the operation can be simplified.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for introducing a liquid sample into a mass spectrometer.

(Prior Art) Liquid samples that are easily vaporized can be vaporized outside the ionization chamber of the mass spectrometer and introduced into the ionization chamber in the same manner as ordinary gaseous samples. In the case of a liquid sample that is difficult to vaporize, for example, when analyzing the outflow fluid of a liquid chromatograph using a mass spectrometer, pass it through the vaporizer nozzle. The column effluent is heated and sprayed into an ionization chamber in the form of a mist under pressure, and vaporized within the ionization chamber, thereby ionizing sample components using various methods. When using this method, it is necessary to inject the sample solution into the ionization chamber in the form of a mist, so a larger amount of sample solution is used than required for mass spectrometry, and most of the sample solution injected into the sample chamber is exhausted by the exhaust pump. are doing. Therefore, a large amount of sample is wasted, and it is difficult to handle a small amount of sample. In addition, there is a large amount of sample and solvent vapor in the ionization chamber compared to the amount required for mass spectrometry, and this enters the mass spectrometer, contaminates the inside of the mass spectrometer, and reduces analysis accuracy. There is. Furthermore, when a mass spectrometer is used as a detector for a liquid chromatograph, the entire amount of liquid effluent from the liquid chromatograph is sent to the ionization chamber of the mass spectrometer, and is then discarded through a pump and used for other purposes, such as the analysis of other species. It is not possible to separate each component separately.

(Problems to be Solved by the Invention) The present invention seeks to provide a method by which a minute amount of a liquid sample can be stably introduced into a mass spectrometer.

(Means for solving the problem) The inside of the ionization chamber or a small chamber connected to the ionization chamber and provided in front of the ionization chamber is maintained in a vacuum, and a liquid sample under atmospheric pressure is passed through a capillary to the atmosphere and inside the ionization chamber. The sample was suctioned by a pressure difference, heated and vaporized in an ionization chamber, and the sample was ionized by an appropriate ionization method.

(Function) The pressure difference between the ionization chamber and the outside world is maintained by the resistance when the liquid passes through the capillary.
If it is about 0 μm, the pressure in the ionization chamber can be easily reduced to 10 to 1
It can be maintained at about 0 Torr. In this case, only a small amount of liquid sample is sucked into the ionization chamber per unit time, and when this method is applied to a liquid chromatograph mass spectrometer, most of the column effluent is supplied to other analytical means or purposes. can do. Since there is no need to pressurize the sample solution, the necessary equipment and operation are greatly simplified.

(Embodiment) Figure 1 shows an embodiment of the present invention. 1 is the outer wall of a mass spectrometer and is connected to an exhaust system not shown. 2 is an ionization chamber into which a capillary 3 is inserted. Capillary 3 has an inner diameter of about 5
The length is about 0 μm, and it extends outside the outer wall 1 and is bent downward. Reference numeral 4 denotes a nut for airtightly fixing the capillary 3 to the penetrating portion of the outer wall 1. By loosening this nut, the capillary 3 can be easily pulled out from the ionization chamber 2 and the inside of the tube building can be cleaned, replaced, etc. A heater 5 is provided outside the ionization chamber 2 so as to surround the capillary 3. A filament 6 is stretched outside the ionization chamber 2, and an electron entrance hole 21 is bored in the side wall of the ionization chamber facing the filament 6. By applying a voltage, electrons emitted from the filament 6 enter the ionization chamber, collide with gas molecules in the chamber, and ionize them. That is, the ionization chamber 2 has the same structure and function as a normal Er ionization chamber.

The end of the capillary 3 outside the outer wall of the mass spectrometer is inserted into the sample solution in a small container 7 containing the sample solution. To exchange the sample, simply replace the small container 7 with a small container containing another sample.
Even if the end of the capillary goes out into the atmosphere and sucks in air when replacing the container 7, the amount is small and does not pose a problem to the mass spectrometer. Of course, when replacing the sample, the inside of the capillary can also be cleaned by inserting the end of the capillary into a cleaning liquid container. When this device is used as a detector for a liquid chromatograph, a capillary 3 whose end is bent upward as shown in FIG. 2 may be used and inserted into the outflow end of the column 8 of the liquid chromatograph. The column effluent is received in a receiver 9, and by replacing the receiver 9 every time the column effluent components change, it is possible to perform fractional collection of sample components while performing mass spectrometry. Prepare a joint 10 into which the end of a capillary 2 is inserted as shown in FIG. 3, and connect one end of the joint to the column outflow end of a liquid chromatograph.
The other end can also be connected to a sample flow tube leading to another analytical device.

The liquid sample is gradually drawn into the ionization chamber through the capillary 3 due to the difference between the atmospheric pressure and the pressure inside the ionization chamber 2.
On the way, it is heated by the heater 5, exits from the end of the ionization chamber of the capillary 3 into the ionization chamber 2 in a vacuum state, and vaporizes. The electrons emitted from the filament 6 collide with this vapor and ionize it, so that the mass spectrometer obtains a mass spectrum of fragment ions obtained by the El ionization method of the sample.

In the above-mentioned embodiment, the sample is drawn directly into the ionization chamber 2; however, as shown in FIG. 4A.

As shown in B, a small chamber 11 is provided in front of the ionization chamber 2 and communicates with the ionization chamber 2, the sample is sucked into this small chamber 11 through the capillary 3, the sample is vaporized in the small chamber, and the vaporized sample is transferred to the ionization chamber. It may be made to flow in. The degree of vacuum in the ionization chamber 2 is 10 10 Torr if the EI method is used.
In the case of a CI method, it is approximately several Torr, which is appropriately selected depending on the ionization method. Regarding the connection between the liquid chromatograph and the capillary 3, only when introducing a sample very easily can the inlet end of the capillary 3 be brought into contact with the outflow end of the column 8, or be inserted lightly, allowing a portion of the column effluent to flow directly into the column. Alternatively, as shown in FIG. 5, a discharge port 81 may be provided on the side surface of the outlet end of the column 3.
The introduction of the sample can also be blocked by inserting the cabilano 3 deeper than the outlet or by returning it toward the end of the column than the outlet.

(Effects of the Invention) According to the present invention, the sample is introduced into the ionization chamber through the capillary at a differential pressure between the atmospheric pressure and the ionization chamber pressure, so a very stable constant flow rate is introduced, and therefore the ionization is also stable. mass spectra with good reproducibility. In addition, since there is no need to pressurize the sample solution, the device configuration for sample introduction, sample processing, and introduction operations are extremely simple, making it easy to handle the sample, and it is easy to connect and disconnect from the liquid chromatograph. Since it can be used as a liquid chromatograph mass spectrometer, it is also easily possible to use the liquid chromatograph and mass spectrometer separately as independent devices. The amount of sample required is extremely small, and there is no waste of sample. Unlike conventional liquid sample introduction devices, a large amount of liquid sample is not introduced into the ionization chamber, and the ionization chamber is in a relatively high vacuum state, so there is no risk of contaminating the mass spectrometer, and the EI ionization method can be applied. , a wealth of analytical information can be obtained.

In addition, a mass spectrometer can be easily used for quantification because a sample with a fixed concentration is continuously introduced and a trapezoidal response is obtained from total ion monitoring or a fragment mass chromatogram, and the sample concentration can be measured from this.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of essential parts of an embodiment of the present invention, Fig. 2 is a side view of the apparatus of the embodiment used to connect a liquid chromatograph and a mass spectrometer, and Fig. 3 is a sectional view of a liquid chromatograph. 4 is a cross-sectional view of another example of the connection between the capillary and the ionization chamber, and FIG. 5 is the capillary end and the outflow end of the liquid chromatography column. It is a side view of another example of connection with. 1...Outer wall of the mass spectrometer. 2...Ionization chamber, 3.
... Capillary, 5... Heater, 6... Heilament, 7... Container, 8... Liquid chromatograph column. 1st vA Agent Patent Attorney Kosuke Agata

Claims (1)

[Claims] The ionization chamber or a small room installed adjacent to the ionization chamber is kept in a vacuum state, and the liquid sample is sucked into the ionization chamber through a capillary extending from the ionization chamber into the atmosphere due to the pressure difference between atmospheric pressure and the ionization chamber. How to introduce a sample into a mass spectrometer.