JPH11108895A - Liquid chromatograph mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the temp. of a desolvating pipe uniform. SOLUTION: Three independent heaters 141-143 separated in the flow direction of a desolvating pipe 13 are provided to the periphery of the pipe 13 and a control part 17 calculates respective heating powers so that the detected temps. by the temp. sensors 151 153 provided to the heaters in a close contact state become predetermined control objective temps. By this constitution, a larger heating current flows to the heater 141 provided on the inlet side of the pipe 13 easy to lower in temp. by the plunging of liquid droplets and the temp. of the desolvating pipe 13 is kept almost uniform as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid chromatograph mass spectrometer, and more particularly to an ionization interface between a liquid chromatograph unit and a mass spectrometer.

[0002]

2. Description of the Related Art FIG. 2 is a schematic diagram showing an example of a liquid chromatograph mass spectrometer (LC / MS). The liquid sample that is temporally separated and eluted from the column 21 of the liquid chromatograph (LC) unit 20 is
And sprayed from the nozzle 12 into the atomization chamber 11 to be ionized. The generated ions pass through a desolvation tube 13 such as a heated capillary provided between the interface section 10 and the mass spectrometry (MS) section 30 to form the MS section 30.
Is sent to

The MS section 30 comprises three chambers, a first intermediate chamber 31, a second intermediate chamber 32, and an analysis chamber 33. A desolvation pipe 13 and a first intermediate chamber are provided between the atomizing chamber 11 and the first intermediate chamber 31. A very small diameter passage hole (orifice) between the chamber 31 and the second intermediate chamber 32
Is provided. While the inside of the atomization chamber 11 of the interface section 10 is maintained at substantially atmospheric pressure, the first intermediate chamber 31 is rotated about 1
rr, and the second intermediate chamber 32 and the analysis chamber 33 are each pumped by a turbo-molecular pump to about 10 ^-3 to 10 ^-4 To
It is evacuated to about rr and about 10 ^-5 to 10 ^-6 Torr.

[0004] The ions that have passed through the desolvation pipe 13 pass through the passage hole of the skimmer 36 and pass from the first intermediate chamber 31 to the second intermediate chamber 3.
2, converged and accelerated by the ion lens 37, and sent to the analysis chamber 33. Then, only the target ions having a specific mass number (mass m / charge z) pass through the quadrupole filter 34 disposed in the analysis chamber 33, and the detector 3
Reach 5 The detector 35 extracts a current corresponding to the number of ions that have arrived.

The interface section 10 generates gas ions by atomizing a sample solution by heating, high-speed gas flow, high electric field, and the like. The interface section 10 performs atmospheric pressure chemical ionization (APCI) or electrospray ionization ( ES
I) is the most widely used. In the APCI, carrier gas ions (buffer ions) generated by corona discharge are chemically reacted with droplets of the sample solution atomized by heating at the nozzle 12 connected to the outlet of the column 21 of the LC unit 20 to perform ionization. Do. Meanwhile, ESI
By applying a high voltage of about several kV to the nozzle 12, a strong unequal electric field is generated near the tip of the nozzle.
The sample solution is separated into electric charges by this electric field, and is torn off and atomized by Coulomb attraction. The solvent in the droplets evaporates upon contact with the surrounding air, generating gaseous ions.

[0006]

In either the APCI or ESI method, the generated ions and the fine droplets before ionization jump into the desolvation tube 13. The desolvation pipe 13 is heated and controlled by an attached heater so as to reach a temperature of about several hundred degrees Celsius. The solvent in the droplets is removed by evaporation. As the size of the droplets becomes smaller, spontaneous droplet destruction due to Coulomb repulsion further progresses, so that generation of target ions is also promoted.

In order to obtain ions stably, it is preferable that the desolvation tube 13 is maintained at a temperature as uniform as possible from the inlet side to the outlet side. However, near the entrance of the desolvation tube 13, heat is taken away by the droplets that jump in,
The temperature tends to decrease. Therefore, in practice, the temperature of the desolvation tube 13 does not reach a uniform temperature in the flow direction, which is one of the causes of deterioration in detection sensitivity. Furthermore, since the amount of heat taken depends on the amount of droplets sprayed from the nozzle 12, the temperature greatly fluctuates especially near the inlet of the desolvation tube 13, and the stability of the detection sensitivity may be impaired.

[0008] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to keep the temperature of a desolvation tube at an optimum temperature and to supply a large number of ions to a mass spectrometer in a subsequent stage. It is an object of the present invention to provide a liquid chromatograph mass spectrometer provided with an ionization interface capable of performing the above.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a method for spraying a sample solution supplied from a liquid chromatograph section from a nozzle to ionize the solution, and performing mass spectrometry through a desolvation tube. In the liquid chromatograph mass spectrometer provided with an interface for conveying to a section, a) a heating section and a temperature detection section provided at at least three places near the inlet, near the outlet, and near the center with respect to the flow direction of the desolvation pipe. Heating means having: b) control means for controlling heating power supplied to each of the heating sections so that the temperatures detected by the respective temperature detection sections are substantially the same predetermined temperature. Features.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The control means receives information on the current heating temperature from a temperature detector provided for each heating means, and supplies heating power to be supplied according to a difference from a target predetermined temperature. Is calculated respectively. The heating unit of each heating means heats the desolvation tube with the heating power specified by the control means.

Usually, in the desolvation tube, more heat is taken away at the inlet side where the droplets enter to evaporate the solvent of the droplets. In addition, since large condensed droplets adhere to the vicinity of the inlet, the heat capacity is large, and the heat capacity decreases toward the back side (that is, the outlet side). For these reasons, if heat is similarly input near the inlet and other parts, the temperature decreases near the inlet. On the other hand, in the interface according to the present invention, when the temperature near the inlet of the desolvation pipe tends to decrease, a large heating power is supplied to the heating unit provided in that part. For this reason, the temperature of the entire desolvation tube is kept extremely stable.

Further, the amount of liquid droplets jumping into the desolvation pipe varies depending on the state of spray from the nozzle, and the amount of heat taken particularly near the inlet of the desolvation pipe also changes due to this effect. However, such a change is quickly followed by increasing or decreasing the heating power, and the temperature of the desolvation tube is kept substantially constant.

In the case of a desolvation tube bent near the inlet, which is used to prevent large droplets and the like from jumping in, it is preferable that the heating section provided near the inlet includes a bent portion. That is, in a desolvation tube having a bent portion on the inlet side, the speed of the droplet decreases at the bent portion when the droplet passes through the desolvation tube, and at that time, evaporation of the solvent is apt to proceed. For this reason, the amount of heat taken from the inner wall of the desolvation pipe tends to increase near the bent portion. Therefore, when the heating section is provided including the bent portion, an appropriate amount of heat can be given to the bent portion, and the temperature of the entire desolvation tube tends to be uniform.

[0014]

According to the liquid chromatograph / mass spectrometer of the present invention, since the temperature of the desolvation tube is maintained substantially uniform, evaporation of the solvent from the droplets and crushing of the droplets in the desolvation tube are achieved. It is performed stably and many ions are introduced into the mass spectrometer. For this reason, the detection sensitivity of ions in the mass spectrometer is improved, which contributes to improvement in accuracy and reproducibility of mass spectrometry.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an LC / MS according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of a main part of an ionization interface in the LC / MS of the present embodiment.

As shown in FIG. 1, the desolvation pipe 13 has an inlet opening substantially perpendicular to the jetting direction of the nozzle 12, and has a bent shape near the inlet. In such a shape,
It is possible to effectively prevent relatively large droplets or neutral molecules from jumping into the desolvation tube 13. The desolvation pipe 13 is divided into three parts, near the inlet, near the center, and near the outlet.
Third heaters 141 to 143 are provided around each heater 141.
To 143 are first to third temperature sensors 15 such as a platinum sensor.
1 to 153 are attached in close contact. The temperatures T1, T2, and T3 detected by the temperature sensors 151 to 153 are input to the control unit 17. The first to third heaters 14
Numerals 1 to 143 denote heater blocks each composed of a resistor, and the heater blocks themselves generate heat when current flows from the first to third current sources 161 to 163.

The control unit 17 determines a heating power P1 to be supplied to each of the heaters 141 to 143 based on a predetermined calculation formula using the detected temperature values T1 to T3 and the control target temperature Ts as parameters.
To P3 are calculated. The above formula can be obtained in advance by a preliminary experiment or the like. First to third current sources 1
61 to 163 are heating electric powers P instructed by the control unit 17;
A heating current is supplied to the heaters 141 to 143 according to 1 to P3. Accordingly, each of the heaters 141 to 143 generates heat so as to approach the control target temperature Ts, and gives heat to the desolvation pipe 13. Note that the entire desolvation pipe 13 is composed of heaters 141 to 143.
When it is configured to be covered with a metal heat equalizing block including the above, the uniformity of heating of the desolvation tube 13 is further maintained.

In the above configuration, the sample solution supplied from the column is sprayed under atmospheric pressure through a small-diameter nozzle 12 heated to an appropriate temperature (for example, 200 to 400 ° C.). The ejected droplet collides with gas molecules at atmospheric pressure, is further crushed into fine droplets, is quickly dried (desolvated), and the sample molecules are vaporized. The gaseous fine particles come into contact with buffer ions generated by corona discharge from the needle-shaped discharge electrode 18 and cause a chemical reaction to be ionized.

Since the inlet side of the desolvation tube 13 is substantially at atmospheric pressure and the outlet side is in a vacuum atmosphere, fine droplets containing the generated ions are sucked into the desolvation tube 13. Desolvation tube 13
For example, several tens of volts having the same polarity as the generated ions.
Voltage is applied. Therefore, the desolvation tube 13
The ions that have entered or the droplets having a biased charge having the same polarity as the ions travel in the desolvation tube 13 toward the outlet while maintaining a predetermined distance from the inner wall of the desolvation tube 13 due to electric repulsion. During that time, the solvent in the droplet evaporates, generating ions.

In the vicinity of the inlet of the desolvation pipe 13, heat is taken away due to the solvent removal of the droplets that have jumped in, and more heat is generated due to the condensation of large droplets adhering to the vicinity of the inlet. Be deprived. For this reason, the second and third heaters 14
The temperature is lower than the temperature of the desolvation tube 13 near 2,143. Since this temperature drop is detected by the first temperature sensor 151, the control unit 17 supplies a control signal to the first current source 161 to supply more heating power. As a result, the amount of heat generated by the first heater 141 increases, and the temperature is maintained near the control target temperature Ts.

Although the above embodiment has an interface configuration based on APCI, the same applies to ESI. Also, between the nozzle 12 and the inlet of the desolvation tube 13, appropriate electrodes and other ion sampling means are inserted so as to guide only droplets and ions of an appropriate size into the desolvation tube 13. It may be configured.

The above embodiment is merely an example, and it is apparent that changes and modifications can be made as appropriate within the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of an ionization interface in a liquid chromatograph mass spectrometer according to one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a liquid chromatograph mass spectrometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 ... Nozzle 13 ... Desolvation tube 141-143 ... Heater 151-153 ... Temperature sensor 161-163 ... Current source 17 ... Control part 18 ... Discharge electrode

Claims (1)

[Claims] 1. A liquid chromatograph / mass spectrometer having an interface for spraying a sample solution provided from a liquid chromatograph section from a nozzle to ionize and transporting the sample solution to a mass spectrometry section via a desolvation pipe, With respect to the flow direction of the desolvation pipe, provided at at least three places near the inlet, near the outlet, and near the center, heating means having a heating unit and a temperature detection unit, and b) a temperature detected by each of the temperature detection units And a control unit for controlling heating power supplied to each of the heating units such that the temperature is substantially the same as the predetermined temperature.