JP2011085547A - Sample heating method for magnetic resonance apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample heating method different from sample heating using conventional temperature-controlled gas in a sample heating method usable for a magnetic resonance spectroscope such as NMR, NQR, and ESR apparatus. <P>SOLUTION: In order to efficiently heat the sample, the sample as well as a conductor are sealed in a sampling tube, and inductive current is then induced in the conductor by rotating the tube in a magnetostatic field, thereby inductively heating the conductor to heat the sample. The sample as well as a resonator are also sealed in the sampling tube, and the inductive current is induced in the resonator by sending electromagnetic waves having a frequency close to a resonant frequency of the resonator from outside of the sampling tube to heat the resonator by induction. The resonator is characterized by receiving external electromagnetic energy through inductive coupling via space. These means enable only the sample to be efficiently heated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sample heating method that can be used in a magnetic resonance spectrometer such as an NMR apparatus, an NQR apparatus, or an ESR apparatus.

  Magnetic resonance spectrometers such as NMR (nuclear magnetic resonance) devices and ESR (electron spin resonance) devices apply a static magnetic field to nuclei and electrons having a spin magnetic moment, and generate a Larmor precession in the spin magnetic moment. Then, by irradiating and resonating with a high frequency of the same frequency as the precession, the analyzer detects an electron or nucleus signal having the spin magnetic moment.

  Magnetic resonance spectrometers often measure magnetic resonance by rotating a sample by blowing a gas onto a sample tube containing the sample. Therefore, in order to control the temperature of the sample to a desired temperature, the temperature of the sample is often controlled by controlling the temperature of the gas blown to rotate the sample to the desired temperature. This technique is generally widely used in solution NMR measurement and solid state NMR measurement.

  In the case of ESR measurement without rotation of the sample, the temperature of the sample is controlled by blowing a gas dedicated to temperature control on the sample instead of the gas for rotating the sample.

  These methods are identical in that the temperature of the sample is changed using a temperature-controlled gas, and is controlled by changing the sample temperature from the outside of the sample tube.

  Also, as a completely different method that does not use a temperature-controlled gas, a method of inductively heating an NMR sample by the same method as a microwave oven using a microwave oscillator and a microwave irradiation coil has been proposed (Patent Document). 1). This method has a great feature in that the sample temperature can be raised in a short time as compared with the method using gas. However, it is only for heating and cannot be used for cooling.

JP-A-5-126828

  By the way, in the conventional sample temperature changing method, since the temperature-controlled gas is sprayed from the outside of the sample tube, it is necessary to use a high-temperature gas when the temperature is increased. For this reason, not only the sample but also peripheral devices such as a gas spray mechanism are exposed to high temperatures.

  These peripheral devices are usually made of a resin, and the heat resistance of this material determines the upper limit of the gas temperature. In other words, sample tubes made of ceramic or glass can withstand high temperatures, but the resin used in the gas spray mechanism cannot withstand high temperatures, and the temperature that the resin can withstand is the upper limit of the temperature. there were.

  Further, in the conventional method, the temperature of the sample coil used for observing the signal from the sample also rises at the same time, resulting in a decrease in detection sensitivity due to an increase in thermal noise.

  The purpose of the sample temperature control apparatus is originally to increase only the temperature of the sample. Nevertheless, these problems are caused by simultaneously increasing the temperature of the peripheral device and the sample coil by blowing hot gas from the outside of the sample tube. That is, the root of all evil is that the sample temperature is controlled by applying heat from outside the sample tube.

  In the present invention, by generating heat from the inside of the sample tube, these problems are avoided, and ultra-high temperature measurement and measurement with high sensitivity are possible. By generating heat from the inside of the sample tube, the temperature rise of the peripheral device can be suppressed. This makes it possible to raise the temperature to the upper limit of the material of the sample tube itself, not the heat resistant temperature of the material resin of the peripheral device. In addition, since the temperature rise of the sample coil can be suppressed, measurement with high sensitivity becomes possible.

  For this purpose, it is necessary to transfer energy into the sample tube in a form other than heat. One method is a method using kinetic energy, and the other method is a method of transmitting electric energy through inductive coupling.

  Since either method can transmit energy to a spatially separated place, the heating element and the outside do not need to be directly thermally coupled. Therefore, the rotation of the sample can be freely performed without restriction, and heat insulation from the outside of the sample tube is easy.

In order to achieve this object, a sample heating method for a magnetic resonance apparatus according to the present invention includes:
It is characterized in that a conductor is enclosed in a sample tube together with a sample, an induced current is induced in the conductor by rotating in a static magnetic field, and the sample is heated by induction heating of the conductor.

  The conductor has a magnetic susceptibility close to that of the sample.

  The conductor is copper.

  In addition, the resonator is enclosed in the sample tube together with the sample, and an induction current is induced in the resonator by irradiating an electromagnetic wave having a frequency close to the resonance frequency of the resonator from the outside of the sample tube, thereby inductively heating the resonator. This is characterized by heating the sample.

  Further, the resonator is characterized in that it receives electromagnetic wave energy from the outside by inductive coupling through a space.

According to the sample heating method of the magnetic resonance apparatus of the present invention,
Since the conductor is enclosed in the sample tube together with the sample, the induced current is induced in the conductor by rotating in a static magnetic field, and the sample is heated by inductively heating the conductor.
The sample can be heated efficiently.

In addition, the resonator is enclosed in the sample tube together with the sample, and an induction current is induced in the resonator by irradiating an electromagnetic wave having a frequency close to the resonance frequency of the resonator from the outside of the sample tube, thereby inductively heating the resonator. Thus, the sample for heating the sample can be efficiently heated.

It is a figure which shows the principle of the sample heating method concerning this invention. It is a figure which shows the structural example of the sample heating method concerning this invention. It is a figure which shows the structural example of the sample heating method concerning this invention. It is a figure which shows the structural example of the sample heating method concerning this invention. It is a measurement example of solid-state NMR based on this invention. It is a measurement example of solid-state NMR based on this invention. It is a figure which illustrates the resonator used for the sample heating method of this invention. It is a figure which shows the principle of the sample heating method using the resonator of this invention.

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

  FIG. 1 is a diagram showing an embodiment of a sample heating method of a magnetic resonance apparatus according to the present invention. In this embodiment, a heating element is enclosed with a sample in a sample tube. For this heating element, a conductor such as a copper piece is used.

When the sample tube is moved / rotated in a static magnetic field, the heating element receives energy from the magnetic flux of the static magnetic field and generates heat. In particular, in the case of solid-state NMR, for example, in solid-state NMR, means for reducing the anisotropy of an NMR spectrum by rotating a sample at a high speed of several tens of kHz around an axis inclined by 54.7 ° with respect to the static magnetic field axis. In solution NMR, the sample is rotated at a low speed of a few tens of Hz, and is used as a means to reduce the inhomogeneity of the static magnetic field. It is a basic operation that is easy to execute.
In order to efficiently generate heat, it is preferable that the long axis of the conductor itself extends long enough to cut the magnetic flux of the static magnetic field. The sample tube does not necessarily need to be insulated, but thermal efficiency is improved when heat radiation to the outside is suppressed by the insulation.

  Use of a conductor having a magnetic susceptibility close to that of the sample is effective because adverse effects due to magnetic susceptibility mismatching can be minimized. It is also possible to combine the present embodiment with the conventional temperature control by gas blowing.

  There can be a plurality of forms of contact between the sample and the heating element. The simplest is to bring the conductor directly into contact with the sample. This is expected to have the highest heat conduction efficiency. The conductor can be arranged at one end or both ends of the sample, and the conductor is not limited to the end of the sample but can be arranged in the sample.

  The number of conductors is not limited to one, and a plurality of conductors can be arranged. The conductor is not limited to a metal piece, but can be used in any form as long as it is a conductor. Plating and vapor deposition of a conductor on a carrier makes it easy to separate and collect the sample and conductor, and is practical. Easy to use. FIG. 2 shows some examples. On the left, one conductor is placed at one end of the sample. In the center, a plurality of conductors are embedded in the sample. On the right is an embodiment in which a conductor is plated and evaporated on a carrier.

  The sample and the conductor need only be in thermal contact, and need not be in direct contact. That is, an embodiment in which a heat conductor is sandwiched between a conductor and a sample can be considered. By avoiding direct contact, it is possible to avoid a chemical reaction or deterioration of the conductor or sample due to contact.

  Also, the use of a thermal conductor close to the magnetic susceptibility of the sample is effective because it can suppress adverse effects caused by the magnetic susceptibility mismatch between the conductor and the sample.

  The conductor can be placed with one or both ends of the sample sandwiching the heat conductor, and not only the end of the sample but also the conductor wrapped in the heat conductor can be placed in the sample It is. The number of conductors is not limited to one, and a plurality of conductors can be arranged. The conductor is not limited to a metal piece, and any conductor such as graphite having an appropriate electrical resistance can be used as long as the conductor is plated. It is easy to separate and collect conductors and is practically easy to use.

  FIG. 3 shows some examples. On the left, one conductor is placed at one end of the sample. In the center, a plurality of conductors are embedded in the sample. On the right is an embodiment in which a conductor is plated and evaporated on a carrier. In the right embodiment, if the orientation of the carrier is reversed, direct contact between the sample and the conductor is also possible.

  Furthermore, the efficiency of heat conduction to the sample can be improved by devising the shape of the heat conductor. For example, as shown in the left example of FIG. 4, if the heat conductor is protruded into the sample, the sample can be heated uniformly and efficiently. Moreover, the same effect is anticipated by arrange | positioning a sample in a heat conductor like the right example of FIG.

  The operation of this embodiment will be described below. It is known that when a conductor is moved and rotated in a static magnetic field, an induced current flows through the conductor in accordance with a change in magnetic flux that cuts the conductor. This induced current is consumed by the resistance of the conductor and dissipated as heat. That is, by moving and rotating the conductor in a static magnetic field, kinetic energy is converted into heat energy, and heat is dissipated from the conductor. In this embodiment, using this principle, a conductor is used as a heating element.

  Movement in static magnetic field → Conductor generates heat due to induced current → Sample temperature rises.

  Sample rotation is a technique commonly used in NMR, and can be realized only by enclosing a conductor without modifying the conventional apparatus. In solid-state NMR, a sample rotation technique called magic angle spinning (MAS) is widely used. However, as long as the magnetic susceptibility tensor is isotropic, the effect of magnetic susceptibility mismatch can be eliminated by MAS. That is, in the case of a solid-state NMR MAS apparatus, the problem of incompatibility of magnetic susceptibility due to a conductor is small.

Examples carried out using a solid-state NMR MAS apparatus are shown below. As a conductor, a copper foil was enclosed in a sample tube together with a sample. In order to observe the sample temperature, lead nitrate was used as a sample, and an NMR signal of ²⁰⁷ Pb nuclei was observed. It is known that the NMR signal of ²⁰⁷ Pb nuclei of lead nitrate changes very sensitively depending on the sample temperature [T. Takahashi, H. Kawashima, H. Sugisawa, T. Baba, Solid State Nucl. Magn. Reson., 15 (1999), 119-123]. Therefore, the sample temperature can be estimated by observing the NMR signal position of the ²⁰⁷ Pb nucleus.

FIG. 5 shows the NMR spectrum of the ²⁰⁷ Pb nucleus when the sample is rotated at 1 kHz. Many artificial peaks called spinning sidebands appear, but the true peak position is the peak position marked with *.

  This is an example in which the upper side has no copper foil and the lower side has a copper foil. No significant difference in peak position and resolution was observed with and without copper foil. The effect of the magnetic susceptibility mismatch caused by inserting the copper foil is eliminated by MAS. Since there is no change in the peak position, it is considered that the heat was not sufficiently generated in the conductor and the temperature did not rise during the low-speed sample rotation of 1 kHz.

Next, FIG. 6 shows the measurement results obtained by increasing the sample rotation speed to 15 kHz. This is an example in which the upper side has no copper foil and the lower side has a copper foil. It can be seen that with the copper foil, the NMR signal position of the ²⁰⁷ Pb nucleus is clearly shifted and the linearity is widely changed. This signal position shift is caused by the temperature rise of the sample and corresponds to a temperature rise of about 15 ° C. The broadening of the line width indicates that there is a spatial distribution in temperature.

  From this result, it was shown that the method of the present invention surely works.

  In this embodiment, a resonator heating element is enclosed in a sample tube together with a sample. An external element that is inductively coupled to the resonator is disposed outside the sample tube. FIG. 7 shows an example of an encapsulating resonator.

  As shown in FIG. 7, the resonator used in the present embodiment can resonate and absorb electromagnetic wave energy radiated by an external element by forming a loop with an inductor L and a capacitor C and forming an LC resonance circuit. It has a configuration.

  When there is dielectric coupling such as M coupling or C coupling between the external element and the resonator, when an electromagnetic wave is applied from the external element, a current flows to the resonator through the space. The absorbed electromagnetic wave energy flows as a current in the LC resonance circuit, is converted into thermal energy by a resistor R inserted in the circuit, and is transmitted to a nearby sample.

  This current becomes maximum when the frequency of the irradiated electromagnetic wave coincides with the resonance frequency of the resonator. Therefore, the frequency of the electromagnetic wave and the resonance frequency of the resonator should be close to each other.

  Such a method of transferring electric energy through a space by dielectric coupling is widely used in, for example, a mobile phone charger, etc. If a storage battery and a rectifier circuit are inserted at the resistor R in FIG. Thus, the structure of the charging mechanism of the mobile phone itself is obtained.

  The principle of this embodiment is shown in FIG. As shown in FIG. 8, a current flows through the resonator by irradiating an electromagnetic wave having a resonance frequency of the resonator through an external element. This current is consumed by the resistance in the resonator and converted to heat.

  The sample tube does not necessarily need to be insulated, but it is advantageous to raise the temperature if the heat radiation suppresses the radiation of heat to the outside. In addition, it is advantageous to use a resonator having a magnetic susceptibility close to that of the sample because the influence of the magnetic susceptibility matching mismatch can be minimized. In addition, if a resonator is made of a material that does not contain the same nuclide as the observation nucleus, no NMR background signal is produced.

  In order to prevent the irradiated electromagnetic wave from interfering with the NMR measurement, it is necessary to use an electromagnetic wave having a frequency separated from the resonance frequency of the observation nucleus or the bond nucleus by at least 100 MHz for irradiation.

  In this embodiment, since a static magnetic field is not necessarily required, it can also be performed in nuclear quadrupole resonance (NQR) that does not use a static magnetic field. Further, unlike the first embodiment, the degree of heat generation of the resonator can be controlled by controlling the intensity of the external electromagnetic wave and turning on / off the electromagnetic wave, so that the temperature control becomes easy.

  This embodiment can be executed simultaneously with the first embodiment. That is, the resonator generates heat as a conductor when executed under sample rotation. Various arrangements can be considered for the arrangement of the resonators, and the arrangement shown in the first embodiment can be used as it is.

  It can be widely used in ESR, NMR, and NQR magnetic resonance apparatuses.

Claims (5)

A magnetic resonance apparatus characterized by enclosing a conductor together with a sample in a sample tube, inducing an induced current in the conductor by rotating in a static magnetic field, and heating the sample by inductively heating the conductor. Sample heating method. 2. The sample heating method for a magnetic resonance apparatus according to claim 1, wherein the conductor has a magnetic susceptibility close to that of the sample. 3. The sample heating method for a magnetic resonance apparatus according to claim 1, wherein the conductor is copper. By enclosing the resonator together with the sample in the sample tube, and irradiating an electromagnetic wave having a frequency close to the resonance frequency of the resonator from the outside of the sample tube to induce an induced current in the resonator and inductively heating the resonator A sample heating method for a magnetic resonance apparatus, characterized by heating a sample. 5. The sample heating method for a magnetic resonance apparatus according to claim 4, wherein the resonator receives electromagnetic energy from outside by inductive coupling through a space.

Images