JP5517086B2 - MAS probe device for solid-state NMR - Google Patents

Description

The present invention relates to a solid state nuclear magnetic resonance (solid state NMR).
More specifically, the present invention relates to nuclear magnetic resonance (MAS) while rotating a solid sample placed in a magnetic field at a high speed around an axis inclined at a predetermined angle (Magic Angle Spinning; MAS) in a solid-state NMR apparatus. NMR) relates to a MAS probe device for measuring signals.
In more detail, the present invention relates to a solid-state NMR MAS probe apparatus comprising a heating mechanism capable of uniformly heating a sample in a cylindrical sample tube to a high temperature. .
More specifically, the present invention relates to a solid-state NMR MAS probe apparatus, wherein the heating mechanism is an infrared heating mechanism.

  In general, in a solid-state NMR MAS probe apparatus, a sample is placed in a cylindrical sample tube made of ceramic or the like, and an NMR spectrum is measured. In solid-state NMR, in order to obtain a sharp NMR spectrum, a sample is accommodated in a sample tube, and the sample tube is inclined at a predetermined angle (magic angle; 54.7 °) with respect to a magnetic field, and the sample tube is maintained in this state. An NMR signal is obtained while rotating (spinning) around the central axis of the plate at high speed. The sample tube also serves as the rotor of the gas bearing, the MAS probe device is supplied with two lines of high-pressure air, one is used to construct the gas bearing that supports the sample tube, and the other is the sample through the turbine. Used as a drive source for rotating the tube. These high-pressure air is heated by a heater attached to the flow path, and is also used as a heat medium for heating the sample.

  The NMR apparatus is set so that the sample temperature can be changed during measurement. For this reason, in the temperature variable MAS probe device conventionally used, the temperature is adjusted by blowing high-temperature air (or a gas such as nitrogen depending on the purpose) onto the sample tube in order to increase the sample temperature. FIG. 1 shows a method of heating a sample with high-temperature air that is most widely used in a conventional solid-state NMR MAS probe apparatus.

The sample (1) is stored in a cylindrical sample tube (2) made of ceramics. A heater (9) is attached to the air flow path (7) supplied to the MAS probe device. A heating wire heater or a ceramic heater is used as the heater (9). The periphery of the heater (9) and the path (7) from the heater to the MAS probe apparatus are appropriately insulated from the surroundings by a heat insulating material (41) such as a heat insulating vacuum or a porous material. When increasing the sample temperature, the heater (9) is energized to increase the temperature of the air supplied to the gas bearing (4), thereby heating the sample tube (2). An electric thermometer (8) such as a thermocouple is installed in the heated gas flow path (7), and its output is used as a reference signal for the temperature control device (50) to provide a negative feedback to control the temperature. I do.

  Due to the heating in this manner, the temperature distribution in the apparatus is in the order of T9 (heater)> T7 (flow path, housing)> T2 (sample tube)> ˜T1 (sample). The surrounding members are exposed to higher temperatures. For this reason, the peripheral member is affected by various thermal factors and must be designed in consideration of the device design. The heating method of this aspect is preferable as a system for heating the sample temperature to a high temperature. This is not an aspect. In addition, NMR measurement handles a high-frequency signal ranging from 10 MHz to 1 GHz according to the purpose, and very high-precision measurement is performed. The obtained NMR signal is strongly influenced by the material and object existing in the vicinity of the sample tube (2) as well as the structure of the housing (20). Therefore, a conductive material typified by a metal that disturbs a high-frequency signal or a material having a large dielectric loss cannot be used even for an insulator.

  Moreover, since each part member and each equipment constituting the apparatus are complicated in shape and require high dimensional accuracy, the constituent materials used for this purpose are required to have good workability. As a structural material for the housing of the MAS probe apparatus, fluororesins having good high frequency characteristics and engineering plastic resins having excellent temperature characteristics and mechanical strength are mainly used.

  Due to such limitations, the maximum temperature in the solid-state NMR variable temperature MAS probe device is conventionally limited by the temperature characteristics of those resin parts that form a flow path of high-temperature air, and is limited to about 150 ° C. Further, since the structural parts corresponding to the flow path are exposed to heat from the heat source and heated, each part is affected by heat and must be designed taking into account thermal expansion. By ignoring this, simply selecting the structural material is expected to hit the technical limits.

  In the nuclide such as hydrogen and carbon, the intensity of the obtained NMR signal is relatively large and the NMR observation is relatively easy, so there are many organic substances mainly composed of these elements so far. Measurements have been made. Since these organic substances are generally decomposed at high temperatures, there has been little demand for measurement at higher temperatures. However, in recent years, an NMR superconducting magnet capable of generating a strong magnetic field of 21.6 T or higher with high uniformity has been developed and put into practical use, and a magnetic quadrupole nucleus that has been difficult to measure with a conventional low magnetic field. NMR measurement has also become possible. The NMR signal obtained as a result of NMR measurement depends on the strength of the magnetic field, and the stronger the magnetic field, the greater the signal strength. As a result, it has become possible to measure many inorganic substances that have been considered difficult to measure due to insufficient sensitivity. However, since the conventional MAS probe apparatus can only heat the heating temperature up to about 150 ° C., there is a limit in measuring the inorganic solid powder. In order to overcome this, it is necessary to heat to a higher temperature, and the development of a solid-state NMR MAS apparatus capable of responding to this is demanded.

  However, the NMR signal is easily affected by magnetic noise, and adjusting the power input to the heater or adjusting the current to adjust the temperature will affect the set measurement magnetic field, resulting in high-precision measurements. It is difficult to heat the sample temperature to a high temperature, for example, because it becomes difficult, which affects various places. Under these circumstances, a standing glass double sample tube is used, and heating means that are independently driven are provided above and below the NMR measurement section, and the flow path design of the heated air is exhausted. High temperature heating is realized by arranging it in a specific order until it reaches the outlet and selecting the material of the heat transfer pipe from gold or the same heat conductivity, heat resistance and non-magnetic metal as gold. It has been proposed (Patent Document 1).

  However, the NMR apparatus according to this proposal is intended to measure a supercritical fluid, not a solid sample, is not a type that rotates a sample tube at a high speed, and the heating method is also basic. Since it is heated when power is turned on, it easily affects the magnetic field, and cannot be applied to a temperature variable MAS probe apparatus for solid-state NMR.

JP 2005-257528 A

  The present invention basically uses the design of the MAS probe apparatus used in the above-described existing NMR measurement as it is, and allows the temperature of the sample to be set to a high temperature exceeding the conventional limit. It is intended to provide a variable MAS probe device.

Therefore, as a result of earnest research in the present inventors, etc., in the temperature variable MAS probe apparatus for solid NMR, the sample in the sample tube is transferred from one end on the central axis to the cylindrical sample tube containing the solid sample. As a result of providing an infrared heating mechanism that irradiates infrared rays toward the sample, the sample temperature can be heated to a higher temperature than before without affecting the magnetic field, and a sharp NMR spectrum can be obtained. It was found that this is a very effective heating method for solid-state NMR measurement.
The present invention has been made on the basis of this finding, and its configuration has the following features.

  The solid-state NMR MAS probe apparatus according to the first aspect of the present invention is the solid-state NMR MAS probe apparatus in which a cylindrical sample tube is rotatably held in a housing so as to rotate at high speed around the cylindrical central axis. A lid made of quartz or quartz glass transparent to infrared rays is provided on one end side of the cylindrical central axis of the tube, and infrared rays are converged from one end side of the cylindrical central axis to the sample in the sample tube through the lid. A heating mechanism for irradiation is provided.

  The solid-state NMR MAS probe apparatus according to the second aspect of the present invention is the sample according to the first aspect of the present invention, wherein the sample tube is an extension of the cylindrical central axis of the sample tube and uses a radiation thermometer on the side opposite to the heating mechanism. A temperature observation mechanism is provided.

In the first aspect of the present invention, the sample can be directly heated without heating the air path or the housing, so that these temperature rises are suppressed.
As a result, the sample could be heated without being restricted by the heating temperature due to the surrounding structure of the sample tube. By converging the infrared rays on the sample, the heating of the sample tube can be reduced, and the sample can be heated to a higher temperature.
As a result, measurement by fixed NMR has become possible in a wide temperature range that could not be measured conventionally.

Conventional probe device Schematic front view showing the MAS probe device of Example 1 Partially cut away enlarged front view showing the sample container of Example 1 The schematic front view which shows the MAS probe apparatus of Example 2. Schematic front view showing the MAS probe apparatus of Example 3 The graph which shows the relationship between the temperature of the sample in Example 2, and the emitted light intensity of an infrared lamp.

  Hereinafter, the present invention will be described based on examples and drawings.

The outline of the NMR probe apparatus according to the present invention is as shown in FIG.
In this embodiment, an infrared lamp (31) is arranged as a heat source on the extension line of the rotation axis of the sample tube (2), and the infrared parabolic reflector (32) is placed at the focal point of the infrared lamp (31). It arranges and constitutes a heating mechanism.
Infrared light is emitted by energizing the infrared lamp (31). The emitted infrared rays are reflected by the reflecting mirror and become parallel rays, and illuminate the bottom of the sample tube (2).
In the vicinity of the bottom of the sample tube (2), a condenser lens (33) adjusted so that the light beam converges near the center of the sample (1) placed at the center of the sample tube (2). The converging structure is configured by being arranged in the housing (20).
The sample (1) is stored in a cylindrical sample container (35) installed at the center of the sample tube (2).

The entire sample container (35) is made of porous ceramics having a low thermal conductivity. However, as shown in FIG. 3, one end surface facing the infrared lamp (31) is opened and quartz or quartz glass is opened. A lid (34) using a material transparent to infrared rays, such as, is closed.
In addition, ribs (36) and (37) having small widths are provided on the outer periphery of the sample container (35), thereby minimizing the contact area with the sample tube (2), and thereby in the sample tube (2) It can be held in.

  In this way, heat conduction from the sample container (35) to the sample tube (2) is prevented so that heat generated by infrared heating of the sample (1) does not propagate to the sample tube (2) and the surrounding structure. I try to minimize it.

  In addition, when the sample (1) easily transmits infrared rays, a small piece of a substance such as ceramics that is easily heated by infrared rays is not mixed in the sample, and the sample (1) is indirectly added. Can be heated.

The temperature of the sample (1) is detected by observing a light beam emitted from the sample according to the temperature with a radiation thermometer (38) installed on an extension of the axis of the sample tube (2). The output of the radiation thermometer (38) is taken out as an electrical signal corresponding to the temperature, and is input to the programmable temperature controller (50) as a reference signal for controlling the output of the infrared lamp. Thereby, the temperature of the sample can be easily maintained at a predetermined set value. Since the temperature indicated by the radiation thermometer is that of the sample container (35) containing the sample near the sample, it does not necessarily match the true sample temperature.
Therefore, using an appropriate standard sample for temperature calibration such as lead nitrate, perform NMR measurement at each temperature in advance, and read the sample temperature from the chemical shift value of the NMR signal, so that the sample temperature and the thermometer It is desirable to obtain a calibration curve with the indicated temperature. In this case, temperature control is performed according to the obtained calibration curve.

In this embodiment, an infrared lamp, a condenser lens, and the like in the heating mechanism are housed in a single box (70), and infrared rays emitted therefrom are guided into a housing (20) by an optical fiber (61), and a sample tube This is an example in which (2) is irradiated.
This will be described below with reference to FIGS.

  In the box (70), a reflecting mirror (32) and an infrared lamp (31) are arranged at the focal point to constitute a heating mechanism for irradiating parallel light rays in a fixed direction. A focusing lens (33) was arranged in the middle of the parallel light irradiation path to form a converging structure in the box (70). Then, one end of the optical fiber (61) is disposed at the focal position by the condenser lens (33), and the other end of the optical fiber (61) is on an extension line of the axis of the sample tube (2) of the housing (20). At the position, the sample tube (2) was arranged to irradiate infrared rays.

The heat rays emitted from the sample tube (2) for temperature control are collected by a lens (64) and sent to a radiation thermometer (38) using an optical fiber (62). 38) and the temperature control device (50) can be freely arranged.
Since the other points are the same as those of the first embodiment, detailed description thereof is omitted.

By doing so, the positional relationship between the housing (20), the heating mechanism, and the converging structure can be freely set, and the present invention can be easily added to the existing NMR apparatus.
FIG. 6 shows how the sample (1) is heated according to this embodiment configured as described above. The graph of FIG. 6 is a graph showing the relationship between the emission intensity of the infrared lamp (31) and the temperature of the sample (1) when the ambient temperature is 120 ° C.

In this embodiment, a mirror surface is used to guide infrared rays to a desired position, which will be described below with reference to FIG.
The reflecting mirror (32) and an infrared lamp (31) at the focal point thereof are arranged at a desired position near the housing (20) to constitute a heating mechanism that irradiates parallel rays in a certain direction.
Reflecting mirrors (71) and (72) are arranged between the heating mechanism and the housing (20) so as to guide the irradiation path of the parallel rays to a condenser lens (33) provided in the housing (20).
The condensing lens (33) is adjusted so that the incident infrared rays converge near the center of the sample (1) placed in the center of the sample tube (2).
Since other points are the same as those of the second embodiment, detailed description thereof is omitted.

Since the solid-state NMR MAS apparatus of the present invention employs an infrared heating mechanism as its sample heating mechanism, the sample temperature is not significantly applied to the members and components arranged in the apparatus. Only made it possible to raise the temperature.
Conventionally, the measurement temperature has become a wall, and it has been a bottleneck, and there was a limit, but the fact that this limit could be exceeded is worthy of evaluation itself, and its significance is extremely large. In the future, the present invention is expected to be used greatly in the fields of measuring instruments and analytical instruments. NMR, which has been used as these instruments, has been used for structure determination and identification in the field of organic compounds and has greatly contributed to its development. However, according to the present invention, higher temperatures can be obtained without generating noise. Since measurement at the level has become possible, it is expected to be used greatly in fields related to research and development of various solid materials such as crystals and amorphous materials. In addition, the present invention makes it possible to obtain various physical property data, greatly contributing to the progress of basic research on solid-state physical chemistry, and new knowledge is expected to be obtained one after another.

1: Sample 2: Sample tube 3: High frequency coil 4: Gas bearing stator 5: Turbine rotor blade 6: Turbine stator 7: Gas flow path 8: Temperature sensor 9: Heater 10: Gas flow path 11: Gas flow control valve 20: Housing 31: Infrared lamp 32: Reflector 33: Condensing lens 34: Transparent lid 35: Sample container 36, 37: Rib 38: Radiation thermometer 50: Temperature controller 61, 62: Optical fiber 63, 64: Lens 70: Box 71, 72: Reflector A: Sample tube rotation axis B: Direction of external magnetic field

Claims (2)

  In a solid NMR MAS probe device in which a cylindrical sample tube is rotatably held in a housing so as to rotate at high speed around the cylindrical central axis, an infrared ray is applied to one end of the cylindrical central axis of the sample tube. In contrast, a lid made of transparent quartz or quartz glass is provided, and a heating mechanism for irradiating infrared rays from one end of the cylindrical central axis so as to converge on the sample in the sample tube through the lid is provided. , MAS probe device for solid-state NMR.   2. The solid-state NMR MAS probe apparatus according to claim 1, wherein a sample temperature observation mechanism using a radiation thermometer is provided on an extension line of the cylindrical central axis of the sample tube and opposite to the heating mechanism. A MAS probe apparatus for solid-state NMR, characterized in that