JP2007225454A - Liquid chromatograph mass analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein high voltage is leaked to the upstream side of a sample at the time of ionization due to the high voltage applied to the leading end of an ESI probe to obstruct ionization, and analysis is stopped, and to eliminate the possibility of an electric shock through the metal piping part arranged on the upstream side of the ESI probe. <P>SOLUTION: The joint 2 arranged to the inlet of the ESI probe 1 is made of a metal and equipped with a means for electrically continuing the sample passed through the joint to the earth of an apparatus main body, and the capillary 4 arranged to the outlet of the ESI probe 1 and the joint 2 are insulated by arranging a piping part including a tube 3 made of a resin between the capillary 4 and the joint 2. The tube 3 is formed into a coil form so as to increase the electric resistance of the sample and increased in its whole length. Accordingly, the possibility of an electric shock on the upstream side of the ESI probe 1 is eliminated and the leak of high voltage is reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid chromatograph mass spectrometer (hereinafter referred to as LC / MS), and more particularly to an interface unit between a liquid chromatograph and a mass spectrometer.

  In LC / MS, a method may be used in which components separated by a liquid chromatograph are ionized under atmospheric pressure and introduced into a mass spectrometer. In this case, an interface for ionizing the components separated by the liquid chromatograph column is required, and several interfaces such as an electrospray interface and an atmospheric pressure chemical ionization interface (APCI) are used as an interface used in LC / MS. There are types.

  FIG. 3 is a diagram showing a general configuration of LC / MS using the ESI method for the interface unit. 20 is a liquid chromatograph, 30 is a mass spectrometer, 40 is an interface unit, and an electrospray ionization unit 42 is arranged, and an ESI probe 43 is arranged in the electrospray ionization unit 42. In addition, a heater mechanism (not shown) is attached to the thin tube 44 disposed behind the electrospray ionization unit 42, which promotes the desolvation of charged droplets generated by the electrospray ionization unit 42. It functions as a desolvation means. In the liquid chromatograph 20, the test liquid injected from the sample introduction unit 23 rides on the flow of the mobile phase 21 sent by the liquid feed pump 22, is separated in the column 24, and passes through the sample pipe 41. Enter the ESI probe 43.

The sample that has entered the ESI probe 43 merges with a nebulizer gas (for example, N 2 gas) at the tip of a thin nozzle (capillary) disposed at the outlet of the ESI probe 43 and is sprayed while being atomized to the atmospheric pressure region. .
Further, a high voltage of about several kV is applied to the tip of the ESI probe 43, and a strong non-uniform electric field is formed at the tip. A part of the droplet ejected while being atomized by this strong electric field is charged. Further, the droplets are further divided by the Coulomb repulsive force of the ions in the charged droplets, and ionization is performed. A part of the droplets enters the narrow tube 44.

  The charged droplets are heated by a heater in the narrow tube 44 to evaporate the solvent, and further collide with other particles to further reduce the size and promote ionization. The generated ions are extracted from the narrow tube 44. To the mass spectrometer 30.

  The mass spectrometer 30 is depressurized by a rotary pump 33 and is further depressurized by turbo molecular pumps 34 and 35. The sample introduced and ionized into the mass spectrometer 30 kept in such a reduced pressure state is converged by the lens effect by the converging lens 31 and the quadrupole rod 32, and is separated and mass-analyzed according to the mass.

As can be seen from the above description, the analytical sensitivity in LC / MS is determined by the efficiency of how much of the sample exiting the liquid chromatograph can be ionized and introduced into the mass spectrometer, and this efficiency is determined by the ESI probe. This depends on the performance of the entire electrospray ionization unit. In view of this, various devices for the configuration around the ESI probe have been made. For example, Ion Evaporation is promoted by maintaining the conditions for the sample to atomize from the tip of the ESI probe, or the conditions for the atomized sample to reach the capillary tube, and the sensitivity of the ion peak of the sample molecule to be detected. To improve. (For example, see Patent Document 1)
JP-A-6-76789

  FIG. 2 is a diagram showing the configuration of a conventional ESI probe. 11 is an ESI probe, 12 is a joint for connecting the sample pipe 41 and the tube 13, and the tube 13 is a resin insulator having a length of 100 mm and a diameter of 0.16 mm, for example, and 14 is arranged at the outlet of the ESI probe 11. It is the installed capillary. The tube 13 and the capillary 14 are connected by a coupler 15, and the sample pipe 41 is a sample introduction pipe for introducing the sample separated by the liquid chromatograph into the ESI probe 11. The sample that has entered the ESI probe 11 passes through the tube 13, merges with a nebulizer gas (for example, N 2 gas) at the tip of the capillary 14, and is sprayed while being atomized to the atmospheric pressure region. A high voltage of about several kV is applied to the tip of the ESI probe 11 in order to ionize the ejected droplet. In the case of this configuration, the high voltage applied to the tip of the ESI probe 11 may leak to the upstream side of the sample and ionization cannot be performed, and the analysis may be stopped. In addition, if a current leaks upstream through the sample, there is a possibility of electric shock through a metal piping component arranged on the upstream side of the ESI probe 11. An object of the present invention is to provide an ESI probe in which analysis does not stop due to a high-voltage leak and no electric shock occurs.

In order to solve the above problems, the present invention relates to an LC / MS provided with an interface unit that ionizes a liquid sample eluted from a liquid chromatograph and introduces it into the mass spectrometer between the liquid chromatograph and the mass spectrometer. In the ESI probe provided in the interface unit, the sample introduction pipe is disposed between the joint of the sample introduction pipe disposed at the inlet of the ESI probe and the capillary for spraying the sample disposed at the outlet of the ESI probe. The tube made of an insulator is formed in a coil shape, has a long overall length, and increases the electrical resistance of the internal sample. Therefore, the leakage of the high voltage applied to the tip of the capillary is reduced, the sample is efficiently ionized, and the analysis does not stop.
Further, the joint that is disposed at the inlet of the ESI probe and connects the sample introduction pipe and the tube is made of metal, and includes means for allowing the sample flowing inside to be conducted to the ground of the mass spectrometer. Therefore, the sample upstream of the joint is not affected by the high voltage applied to the tip of the capillary, and there is no possibility of electric shock from piping parts upstream of the ESI probe.

  According to the present invention, in the LC / MS provided with an ESI probe in the interface part, there is no possibility of electric shock through the metal piping parts, and the ionization of the sample is always efficiently performed by reducing the leakage of high voltage, This has the effect of improving the sensitivity and efficiency of mass spectrometry.

  Between the capillary for spraying the sample arranged at the outlet of the ESI probe and the metal joint of the pipe for introducing the sample arranged at the inlet of the ESI probe, piping is made with piping parts including a tube made of PEEK resin. And insulated.

  The size of the ESI probe is limited due to the overall structure of the LC / MS, and the PEEK resin tube disposed inside the ESI probe is meanderingly placed inside the ESI probe in order to increase the overall length. .

  Examples of the present invention will be described below. FIG. 1 is a diagram showing the configuration of the present invention. Reference numeral 1 is an ESI probe, and 2 is a metal joint that connects the sample pipe 41 and the tube 3 and is connected to the ground of the apparatus main body. The tube 3 is an insulator made of resin, and is stored in the ESI probe 1 and formed in a coil shape so as to lengthen the entire length. For example, the tube 3 has a total length of 400 mm and a diameter of 0.08 mm. Reference numeral 4 denotes a capillary disposed at the tip of the ESI probe 1, and the tube 3 and the capillary 4 are connected by a coupler 5. The sample pipe 41 is a sample introduction pipe for introducing the sample separated by the liquid chromatograph into the ESI probe 1. The sample that has entered the ESI probe 1 passes through the tube 3, merges with a nebulizer gas (for example, N 2 gas) at the tip of the capillary 4, and is sprayed while being atomized to the atmospheric pressure region. A high voltage of about several kV is applied to the tip of the ESI probe 1.

  Since the present invention has the above-described configuration, the length is four times that of the tube 13 and the sectional area is ¼ compared to the conventional ESI probe 11. In general, since the electrical resistance of the sample in the tube is proportional to the length and inversely proportional to the cross-sectional area, the electrical resistance of the sample in the tube 3 is 16 times that of the tube 13. The amount of leakage of the high voltage in the ESI probe 1 to the upstream side of the sample is reduced as the electrical resistance of the sample is increased as compared with the ESI probe 11, and the sample is stably ionized. The joint 2 is made of metal and is connected to the ground of the mass spectrometer, and the internal sample becomes a ground potential when contacting the metal joint 2, and the influence of the high voltage is the sample upstream of the joint 2. It does not extend to. Therefore, there is no electric shock through the metal piping parts arranged on the upstream side of the ESI probe 1.

  The ESI probe 1 of the present invention is disposed and functions as the ESI probe 43 of FIG. 3 as a component of LC / MS. That is, the sample introduced from the liquid chromatograph 20 through the sample pipe 41 to the ESI probe 43 merges with the nebulizer gas at the capillary at the tip of the ESI probe 43 and is sprayed while being atomized into the atmospheric pressure region. Further, some of the droplets ejected while being atomized by a strong unequal electric field formed by a high voltage applied to the tip of the ESI probe 43 become charged droplets, and ions in the charged droplets. Due to the coulomb repulsive force, the droplets break up and ionize, and a part of them enters the narrow tube 44. The charged droplets are further miniaturized in the narrow tube 44 to promote ionization, and the generated ions are extracted from the thin tube 44 and sent to the mass spectrometer 30 where they are separated according to mass and subjected to mass analysis.

  In the embodiment shown in FIG. 1, the tube is made of resin, but any material other than resin can be used as long as it is an insulator. In the illustrated example, the tube is formed in a coil shape, but may be a bent shape as long as it is a long tube that can be stored in the ESI probe, and its shape is not limited. The present invention includes these modifications.

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

It is a figure which shows the structure of this invention. It is a figure which shows the structure of the conventional ESI probe. It is a figure which shows the general structure of LC / MS.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ESI probe 2 Joint 3 Tube 4 Capillary 5 Coupler 11 ESI probe 12 Joint 13 Tube 14 Capillary 15 Coupler 20 Liquid chromatograph 21 Mobile phase 22 Liquid feed pump 23 Sample introduction part 24 Column 30 Mass spectrometer 31 Converging lens 32 Quadrupole Rod 33 Rotary pump 34 Turbo molecular pump 35 Turbo molecular pump 40 Interface unit 41 Sample pipe 42 Electrospray ionization unit 43 ESI probe 44 Narrow tube

Claims (2)

  In a liquid chromatograph mass spectrometer in which a liquid sample eluted from a liquid chromatograph is ionized by an electrospray probe (hereinafter referred to as an ESI probe) and introduced into a mass spectrometer, a sample introduction pipe disposed at the inlet of the ESI probe A liquid chromatograph mass spectrometer characterized in that a tube disposed between a joint and a capillary for spraying a sample disposed at an outlet of an ESI probe is formed in a coil shape.   The joint provided at the inlet of the ESI probe and connecting the sample introduction pipe and the tube is made of metal, and is provided with means for conducting the sample flowing inside to the ground of the mass spectrometer. The liquid chromatograph mass spectrometer according to 1.

Images