JPH01219557A - Chromatography/mass spectrometer - Google Patents

Abstract

PURPOSE:To enable exact analysis with high reliability by connecting a microchromatography and a mass spectrometer by an interface and setting an interface temp. and ion source temp. respectively at optimum temps. CONSTITUTION:A chromatographically separated 13 sample passes a capillary 21 and is injected together with mobile phase to an ion source 31 of the mass spectrometer 30. The capillary 21 is kept heated uniformly to the optimum temp. by a heat medium flowing in a jacket 23 through a pipe 22. Namely, the heat medium is kept circulated in an interface heating unit 20 via a pipe 24 and the temp. thereof is detected by a temp. detector 29 and is inputted to a heater control unit 26, by which the heater 28 in a heat medium tank 27 is feedback-controlled to attain the preset optimum temp. (determined by the kind of the mobile phase solvent, etc.). The ion source 31 is independently heated to the optimum temp. by a heater 32. The stable ion source pressure is, therefore, obtd. and the mass spectra of good reproducibility are obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a chromatography/mass spectrometer,
In particular, it relates to an interface in a system that directly connects microliquid chromatography and mass spectrometry.

[Conventional technology]

Liquid chromatography (hereinafter simply referred to as chromatography) is a method for separating complex mixed systems such as biological substances9.
Recently, a method (hereinafter referred to as LC) that directly connects this chromatography and a mass spectrometer to perform integrated separation of mixed components and high-sensitivity detection for mixed samples has been developed.
/MS) has been developed.

In such an LC/MS system, in order to continuously vaporize and introduce sample components that are eluted together with the mobile phase under atmospheric pressure into the mass spectrometer under reduced pressure, an interface is provided between the two. It becomes necessary. here,
In the case of gas chromatography, the mobile phase is a gas and the flow rate is low, so the interface can be easily implemented, but in liquid chromatography, the mobile phase is a liquid and the flow rate is usually high. ,
Directly connecting this to a mass spectrometer requires a complicated interface such as dividing the mobile phase and introducing it.

In FIG. 5, which shows a schematic diagram of this type of system, 10 is a chromatography system, in which a sample is added into a mobile phase by a sample injection means 12 and chromatographically separated by a separation column 13.

This chromatographically separated sample is introduced into the ion source 31 of the mass spectrometer 30 via the interface together with the mobile phase, and then subjected to mass separation by the separation system 32.

By the way, recently, microchromatography, in which columns used in chromatography are miniaturized, has been proposed. This microchromatography has various advantages such as the use of a small amount of mobile phase, making it possible to use an expensive mobile phase. It has the advantage of being easy to connect directly. That is, according to this microchromatography, the mobile phase flow rate of the column is several μj! /win, the entire effluent can be introduced into the mass spectrometer's ion source to generate electronic surface II (El
) mode also has the advantage of being able to ionize.

[Problem to be solved by the invention]

As is well known, in a mass spectrometer, data with good reproducibility cannot be obtained if the degree of vacuum (pressure) of the ion source changes, so the pressure of the ion source must be maintained at a constant pressure. However, in the LC/MS system using microchromatography (hereinafter referred to as micro LC/MS system) as described above, a constant amount of mobile phase is not always supplied to the ion source, and the pressure of the ion source fluctuates. The problem is that you end up doing it. This is a situation where the mobile phase is unstable (for example, a state where gas and liquid are mixed) due to bumping occurring or unstable temperature control within the capillary that makes up the interface.
It is thought that this occurs when the ion source is sent to the ion source.

Therefore, in order to obtain a stable ion source pressure in a micro LC/MS system, it is important to keep the temperature of the mobile phase in the capillary, that is, the interface temperature, at an optimal temperature and always supply a stable mobile phase to the ion source. It is. Conventionally, a pipe is installed outside the interface capillary, and the capillary is heated by the heat transmitted to this pipe from the ion source of the mass spectrometer needle to control the temperature. In order to obtain this, it was necessary to change the ion source temperature.

Therefore, when using a mobile phase for chromatography, such as a mobile phase that easily vaporizes, it is necessary to set the ion source temperature low. If the ion source is kept at a low temperature, it will easily adsorb to the ion source and fall off during the measurement, increasing the background in the analysis results, or obtaining a spectrum with too strong parent ion intensity. The obtained spectrum differs greatly from the spectrum obtained with a conventional device that directly connects a gas chromatography and mass spectrometer (the ion source is at a high temperature), making it difficult to compare the two and making it difficult to obtain accurate accuracy. There was a problem that high-quality analytical results could not be obtained.

The present invention has been made in view of the above points, and provides a chromatography/mass spectrometer that can set the interface temperature and ion source temperature to optimal temperatures, and perform accurate and highly accurate analysis. The purpose is to

[Means to solve the problem]

Chromatography/mass spectrometry according to this invention -
The analyzer includes a capillary for introducing a chromatographically separated sample into the mass spectrometry needle together with a mobile phase, and a heating medium disposed around the capillary to heat the mobile phase in the capillary. an interface temperature measuring means for obtaining temperature information of the mobile phase in the capillary by detecting the temperature of the heating medium, and controlling the temperature of the heating medium according to the temperature information. A temperature control means is provided, and an interface heating means is configured separately from the ion source heating means.

Further, the temperature control means in the chromatography/mass spectrometer is provided with a temperature setting means for setting the temperature of the heat medium in stages when setting a heat medium temperature that provides an optimal interface temperature, and a temperature setting means for setting the temperature of the heat medium in stages, and A degree of vacuum measuring means detects the degree of vacuum of the ion source by detecting the ion signal of the mobile phase solvent, and the optimum set temperature with the smallest fluctuation range is calculated by calculating the fluctuation of this detection signal for a predetermined time for each set temperature. A calculation means for determining the temperature is provided, and this optimum set temperature is set in the temperature control means.

[Effect]

In this invention, the mobile phase in the interface is heated by a heating medium, and the temperature of the mobile phase is measured, for example, by detecting the heating medium temperature, so that the mobile phase temperature becomes the optimum temperature. Since the temperature of the heat medium is controlled, it is possible to set the interface temperature to the optimum temperature independently of the ion source temperature,
Highly accurate analysis results can be obtained.

In addition, when determining the optimal temperature of the interface by calculation, the optimal interface temperature is automatically set without relying on experience, making it possible to easily conduct more accurate analysis, especially when using the gradient method. Even when the composition of the mobile phase solvent changes continuously, the interface temperature can always be adjusted to the optimum value.

C Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a micro LC/MS according to an embodiment of the present invention, and this micro LC/MS includes a micro chromatography section 10, a mass spectrometer 30, and an interface connecting these. , and an interface heating unit 20 for heating this interface.

The microchromatography section 10 and the mass spectrometer 30 are constructed in substantially the same manner as conventional devices. That is, the microchromatography part 10 includes a pump 11. which discharges a mobile phase solvent. sample in this mobile phase solvent
Injector 12. and a capillary column 13 for chromatographically separating the sample. The mass spectrometer 3'O also includes an ion source 31.0 that ionizes the sample separated by the microchromatography section 10. Ion source heater 32. Lens for narrowing down and extracting ions 33. A quadrupole 34 for separating ionized samples according to their mass numbers. Deflector 352 for removing noise from light, X-rays, etc. Detector 36 for detecting ions in the separated sample. and data processing section 3
It consists of 7.

The microchromatography part 10 and the mass spectrometer 3
0 through an interface, and this interface connects the capillary column 13 and the capillary 21 as a resistance tube. and a pipe 22 through which the capillary 21 is inserted, and from this pipe 22 the capillary 2
It is designed to transfer heat to 1.

The temperature of this interface is controlled independently by the interface heating unit 20. Next, the interface heating unit 20 will be described as follows: The interface pipe 22
A jacket 23 through which a heat medium flows is disposed around the jacket 23, and a heat medium pipe 24 is connected to the jacket 23. The heat medium is heat medium tank 2
7 and is configured to be pumped into the jacket 23 by a pump 25. A heater 28 is provided in the heat medium tank 27, and a heater control unit 26 for controlling the heater 28 is provided. In addition, in the middle of the flow path of the heat medium pipe 24,
A temperature detector 29 for detecting the temperature of the heat medium is provided, and this detection signal is connected to a control signal input terminal of the heater control unit 26.

Next, the operation will be explained. The operations of the microchromatography section 10 and the mass spectrometer 30 are similar to those of the conventional apparatus, and the operations of these sections will be briefly explained.

First, a constant amount of mobile phase solvent of about several μl/sin is discharged from the pump 11. After the samples are added to the solvent in the injector 12, they are delivered to the capillary column 13 for chromatographic separation. This chromatographically separated sample is sequentially transferred to joint 14. It passes through the capillary 21 and is sent to the ion source 31 of the mass spectrometer 30 together with the mobile phase.

At this time, the capillary 21 is heated to an optimum temperature by the heat medium flowing inside the jacket 23 through the pipe 22. That is, the temperature of the mobile phase within the capillary 21 for obtaining a stable ion source pressure can be determined empirically through experiments and the like, and this temperature varies depending on the type of mobile phase solvent and the like.

Therefore, first, determine the optimal interface temperature depending on the equipment to be used, the type of mobile phase solvent, etc., determine the heat medium temperature to obtain this optimal interface temperature, and then set this temperature value in the heater control unit 26. In the interface heating unit 20, the heat medium is passed through the heat medium pipe 24 to the tank 27. Pump 25. It circulates between jackets 23, and its temperature is detected by a temperature sensor 29. This temperature detection result is input to the heater control unit 26, and the heater 28 is feedback-controlled so that the temperature always corresponds to the preset optimal interface temperature.

The solvent and sample heated to the optimum temperature by the interface heating unit 20 in this manner are injected into the ion source 31 of the mass spectrometer 30. This ion source 3
1 is heated by an ion source heater 32 independently of the interface, and the sample injected through the interface is ionized by the ion source 31 to achieve high sensitivity and high resolution. Then, the light is focused by the lens 3 and drawn out to the quadrupole 34 side. This quadrupole 34 has various DC voltages and high frequency voltages superimposed on each other, and the ions sent into the center of the quadrupole 34 only exhibit stable vibrations of ions with a specific mass number. taken out repeatedly. The course of the ions thus mass-separated is bent by a deflector 35 to remove noise such as light and X-rays, and the ions are sent into a detector 36. The ions of this sample are reflected and amplified by a plurality of dynodes that make up the detector 36, and are finally extracted as a current and sent to the data processing unit 3.
Spectral analysis processing is performed in step 7.

In this embodiment, since the interface heating unit 20 is provided, the ion source temperature and the interface temperature can be independently set to optimum temperatures. Therefore, it is possible to obtain a stable ion source pressure and a mass spectrum with good reproducibility. In addition, adsorption of the sample to the ion source does not occur, and comparison with mass spectra obtained with conventional gas chromatography/mass spectrometry (GC/MS) can be easily performed.

In addition, since the heat medium is heated by flowing through the jacket 23, uniform heating can be achieved and the ion source pressure can be maintained more stably than in a method in which the pipe 22 is directly heated with a heater. In addition, it is possible to eliminate the risk of explosion due to leakage of the mobile phase in this part.

Furthermore, when the composition of the mobile phase solvent changes continuously, such as in the Grashed method, by setting a temperature program in advance accordingly, the interface temperature can always be kept appropriate for the solvent composition.

FIG. 2 shows the apparatus shown in FIG. 1 in which the optimum interface temperature is automatically set. That is, in the micro LC/MS shown in FIG. 1, the interface temperature can always be feedback-controlled to a preset optimum temperature, but the preset optimum temperature is determined by experience. Therefore, in the micro LC/MS shown in FIG. 2, the optimum interface temperature can be easily and automatically set without relying on experience.

By the way, as mentioned above, the optimal interface temperature is closely related to the pressure of the ion source, that is, the degree of vacuum.
It is considered that it is sufficient to measure the degree of vacuum of this ion source and perform feedbank control. However, it is difficult to directly measure the degree of vacuum in the ion source. Therefore, we focused on the fact that fluctuations in the degree of vacuum of the ion source correspond to fluctuations in the ion signal of the mobile phase solvent, and if we performed feedback control by detecting this ion signal, we could easily achieve the above objective. becomes possible.

In the apparatus shown in FIG. 2 for realizing this, the same reference numerals as in FIG. 1 indicate the same parts. Reference numeral 40 denotes an optimum temperature calculation unit that obtains the ion signal from the detector 36, calculates the optimum interface temperature, and sets this in the heater control unit 26.

In FIG. 3 which shows a functional block diagram of the optimal temperature calculation unit 40, 45 sets the temperature in stages from the initial value to the maximum value, and sets the temperature in stages to the heater control unit 45.
6, a signal amplification unit 41 that amplifies the signal from the detector 36, and 42 a fluctuation range that calculates the fluctuation of the amplified signal for a predetermined time for each temperature set stepwise. The calculation unit 43 is a memory that stores the fluctuation range calculation values for each temperature. Further, 44 is a minimum fluctuation width calculating section, which stores the contents of the memory 43 and the temperature setting section 4.
5, it calculates the temperature (optimal temperature) corresponding to the signal with the minimum fluctuation range, and sets this temperature in the temperature setting section 45.

Next, the optimum temperature calculation operation of the apparatus shown in FIG.
The explanation will be given according to the flowchart shown in the figure.

First, in step 51, the initial value t of the set temperature is determined.

and set memory address n-1. The initial value t, maximum value t, and □ of the set temperature are 0, which are known in advance through experiments, etc. Next, the temperature 1-1 is set in the heater control unit 26.
．． At this set temperature t, mass spectrometry is performed in the same manner as shown in the apparatus shown in FIG. 1, and when a steady state is reached, ions of the sample are detected by the detector 36. The detected ion signal is input to an optimum temperature calculation unit (40) and amplified by a signal amplification section (41). Then, the fluctuation range of this amplified signal over a certain period of time is determined by the fluctuation range calculation unit 42 (step 53), and
This calculated value is stored in the address "1" of 3 (step 54), the set temperature t=t, +Δt, and the memory address n=n+ 1 (step 55), so that the set temperature is the highest temperature 1-1. .

The above operation is repeated until the number reaches 8 (step 56).

In this way, the preset temperature range t.

When the signal fluctuation width for each temperature at ~t, □ is determined, all contents of the memory 43 are read out, the values are compared (step 57), and the heating temperature at which the fluctuation width is minimized is set as the optimum temperature. settings in the control unit 26 (step 58).

In this embodiment, in addition to the interface heating unit 20, an optimum temperature calculation unit 40 for calculating the optimum interface temperature using the fluctuation range of the ion signal is provided, so that the apparatus shown in FIG. In addition to obtaining similar effects, the interface temperature can be determined automatically without relying on experience, and mass spectra with better reproducibility can be obtained. In particular, when the composition of the mobile phase solvent changes continuously, such as in a gradient method, the interface temperature can always be set to the optimum temperature.

In each of the above embodiments, the heater is controlled to control the temperature of the heat medium, that is, the interface temperature.
A flow rate control valve may be provided at the outlet of the pump 25 to control the flow rate of the heat medium to control the interface temperature, and the same effects as in each of the embodiments described above can be obtained.

Further, in each of the embodiments described above, the temperature detector 29 is provided in the middle of the flow path of the heat medium pipe 24 to detect the temperature of the heat medium to control the heater.
A temperature detector may be provided on the inner wall of the capillary 21, and may be installed at any location where the temperature of the mobile phase within the capillary 21 can be determined.

In addition, in the embodiment shown in FIG. 2, the degree of vacuum in the ion source is detected by monitoring the ion signal obtained by the detector 36, but of course a vacuum gauge or the like is used to directly detect the degree of vacuum in the ion source. Further, in the optimum temperature calculation unit 40 in the above embodiment, the entire range of fluctuation of the signal at each set temperature is stored in the memory 43.
Once stored in The contents of the memory may be updated, and various configurations are possible.

Further, in each of the above embodiments, a mass spectrometer using a quadruple oscillator was shown, but it goes without saying that other magnetic field deflection type mass spectrometers may be used.

Of course, the interface heating unit and optimum temperature calculation unit of the present invention can also be applied to a QC/MS direct interface.

〔Effect of the invention〕

As described above, according to the present invention, a heating section through which a heating medium flows is provided around the capillary that directly connects a chromatography and a mass spectrometer, and the temperature of the heating medium is detected. Since the temperature of the mobile phase flowing through the capillary is measured and the temperature of the heating medium is controlled according to the detection result, the ion source and the interface can be set to the optimum temperature independently. This has the effect of allowing analysis to be performed with good reproducibility and high reliability.

In addition to the above-mentioned device, the present invention also includes a temperature setting means for setting the temperature of the heat medium stepwise, a degree of vacuum detection means for detecting the degree of vacuum of the ion source at each stepwise temperature, and a degree-of-vacuum detection means for detecting the degree of vacuum of the ion source at each stepwise temperature. In addition to calculating the fluctuation of the detection signal over a certain period of time, we have provided a calculation means that determines the optimal set temperature with the smallest fluctuation range, so even if the mobile phase solvent etc. changes, it can be automatically performed without relying on experience. The optimum interface temperature can be set, and mass spectra with good reproducibility can always be obtained.

[Brief explanation of the drawing]

FIG. 1 shows a chromatography system according to an embodiment of the present invention.
A schematic configuration diagram of a mass spectrometer. Figure 2 is a diagram of the configuration when an optimum temperature calculation unit is installed in the apparatus shown in Figure 1.
Figure 4 is a functional block diagram of the optimal temperature calculation unit of the apparatus shown in the figure, Figure 4 is a flowchart diagram for explaining its operation, and Figure 5 is a configuration diagram showing a general chromatography/mass spectrometer direct connection system. . DESCRIPTION OF SYMBOLS 10... Chromatography part, 20... Interface heating unit, 21... Capillary, 22...
... Pipe, 23 ... Jacket, 24 ... Heat medium pipe, 25 ... Pump, 26 ... Heater control unit, 27 ... Heat medium tank, 28 ... Heater,
29... Temperature detector, 30... Mass spectrometer, 40.
...Optimum temperature calculation unit, 41...Signal amplification section, 4
2... Fluctuation range calculation unit, 43... Memory, 44...
Minimum fluctuation range calculation section, 45...temperature setting section. f, Figure 33] 44 Figure 5

Claims (2)

[Claims] (1) Directly connect chromatography and mass spectrometer,
A chromatography/mass spectrometer that analyzes a mixed sample includes a capillary for introducing the sample chromatographically separated by the chromatography into the mass spectrometer together with a mobile phase; a heating part through which a heat medium flows to heat the mobile phase in the capillary; an interface temperature measuring means for obtaining temperature information of the mobile phase in the capillary; and temperature control of the heat medium in accordance with the temperature information. A chromatography/mass spectrometer characterized by comprising temperature control means for controlling the temperature. (2) The temperature control means includes a temperature setting means for setting the temperature stepwise, and a temperature setting means for detecting the degree of vacuum of the ion source portion of the mass spectrometer for each stepwise set temperature. A degree of vacuum measuring means calculates the fluctuation of the degree of vacuum detection signal for a predetermined period of time for each of the set temperatures, and controls the temperature by using the temperature setting means to determine the optimum set temperature at which the range of fluctuation of this detection signal is the smallest. 2. The chromatography/mass spectrometer according to claim 1, further comprising calculation means set in said means.