JP2005140651A - Probe for nmr - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a probe for NMR capable of efficiently detecting NMR signals in low frequency and high frequency bands from a sample including at least two nuclides. <P>SOLUTION: The probe for NMR 4 which is a probe for NMR detecting NMR signals from two nuclides, is provided with a first sample coil composed of at least one sample coil; and a second sample coil and a third sample coil which are serially connected to both ends of the first sample coil. When detecting an NMR signal of a first nuclide, the first, second and third sample coils are brought to totally operate as a lumped parameter circuit, and the NMR signal is detected from a resonance frequency in the low frequency band. When detecting an NMR signal of a second nuclide, the second and third sample coils are brought to operate as a rejecting circuit which blocks and reflects high frequency signals having a resonance frequency in the high frequency band, and the NMR signal is detected from the resonance frequency in the high frequency band by using the first sample coil. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an NMR probe for detecting an NMR signal from a sample containing at least two nuclides.

In the field of NMR spectroscopy, it may be necessary to detect NMR signals from multiple nuclides. For example, in solid high-resolution NMR spectroscopy, cross polarization may occur from ¹ H nucleus to heteronuclear X. In such a case, it is necessary to detect NMR signals of both ¹ H nuclei and X nuclei.

Here, the resonance band of the NMR signal differs depending on the nuclide. For example, ² D, ¹³ C, ¹⁵ N, ³² P, low γ nuclides, etc. generate NMR signals in the low frequency (LF) region, and ¹ H, ¹⁹ F, ³¹ P, etc. in the high frequency (HF) region. An NMR signal is generated. When such NMR signals in the LF region and the HF region are to be observed simultaneously, an NMR probe that can handle signals in both these bands is required.

  FIG. 1 is a diagram showing a schematic configuration of a conventional NMR probe. The NMR probe includes an HF region signal detection unit 101 that detects an HF region NMR signal and an LF region signal detection unit 102 that detects an LF region NMR signal.

The HF region signal detection unit 101 assumes a ¹ H nucleus or a ¹⁹ F nucleus, and sets a resonance frequency by a parallel resonance circuit including a sample coil L101 and a capacitor C101 arranged in parallel thereto. Further, the resonance frequency can be adjusted by the variable capacitors C111 and C112. As the capacitor C101, a ceramic chip capacitor having a high Q value and a high withstand voltage function is used.

The LF region signal detection unit 102 has an appropriate circuit arrangement depending on various types to be observed, but here, a general circuit used when measuring ¹³ C or the like is shown. The LF region signal detection unit 102 sets a resonance frequency by a parallel resonance circuit including a sample coil L100 and a variable capacitor C100 arranged in parallel thereto.

Thus, for example, if NMR signals appearing separately in the LF region and the HF region, such as NMR signals of ¹³ C nuclei and ¹ H nuclei, are to be observed simultaneously, the conventional NMR probe uses the LF region and the HF region. A separate sample coil was provided for each band signal, and a separate detection circuit was also prepared.

  As described above, since the conventional NMR probe has a plurality of sample coils and a plurality of detection circuits, depending on the nuclide, NMR signals are detected in different observation modes. A complicated calibration was required.

Further, although a technique has already been disclosed in which the sample coil of the HF region signal detection unit 101 is also used for detection of NMR signals of both ¹³ C and ¹ H nuclides, this technique uses a dummy coil in the circuit. It was necessary to insert the signal, and the reduction in detection efficiency was inevitable (see, for example, Patent Document 1).

Japanese Patent Publication No. 58-24738.

  As described above, conventionally, when the NMR signals in the LF region and the HF region are simultaneously observed, the sample coil and the detection circuit corresponding to the signals in the LF region and the HF region are separately prepared, or the efficiency is increased in the circuit. It is necessary to insert a dummy coil that lowers the temperature. In either case, the detection of NMR signals in the LF region and the HF region inevitably requires a circuit configuration in which mutual efficiency cannot be sufficiently obtained, which causes a decrease in efficiency.

  In view of the above points, an object of the present invention is to provide an NMR probe capable of efficiently detecting NMR signals in the LF region and the HF region from a sample containing at least two nuclides.

In order to achieve this object, the NMR probe of the present invention comprises:
In an NMR probe that detects NMR signals from two nuclides,
A first sample coil comprising at least one sample coil; and second and third sample coils connected in series at both ends of the first sample coil;
When detecting the NMR signal of the first nuclide, the first, second and third sample coils are combined and operated as one lumped constant circuit, while the NMR signal is generated at the resonance frequency in the low frequency range. Detect
When detecting the NMR signal of the second nuclide, the second and third sample coils are operated as a rejecting circuit that cuts off and reflects a high frequency having a resonance frequency in a high frequency range. The sample coil is configured to detect an NMR signal at a resonance frequency in a high frequency range.

  Further, the second and third sample coils are high-frequency λ / 4 resonators having a resonance frequency in a high frequency range.

Further, the first species is characterized in that a ^{2 D, 13 C, 15 N} , 32 P, and a low γ nuclides.

The second nuclide is ¹ H, ¹⁹ F, and ³¹ P.

A first sample coil comprising at least one sample coil;
A capacitive element that is connected in series to both ends of the first sample coil and that forms a series resonant circuit for high frequencies in the high frequency range together with the first sample coil;
It is connected in series to both ends of the first sample coil, and operates as a rejecting circuit that blocks and reflects high frequencies from the first sample coil side for high frequencies in the high frequency range, For high frequencies, the second and third sample coils that operate as one lumped constant circuit by combining the first sample coils;
The second and third sample coils are connected in series to the connection end opposite to the connection end of the first sample coil, and together with the first, second, and third sample coils, A capacitive element forming a series resonant circuit for high frequencies;
A high frequency injection terminal in a high frequency range and a high frequency injection terminal in a low frequency range are provided.

  Further, the second and third sample coils are high-frequency λ / 4 resonators having a resonance frequency in a high frequency range.

Further, the first species is characterized in that a ^{2 D, 13 C, 15 N} , 32 P, and a low γ nuclides.

The second nuclide is ¹ H, ¹⁹ F, and ³¹ P.

  In an NMR probe for detecting NMR signals from two nuclides, a first sample coil comprising at least one sample coil, and second and third sample coils connected in series to both ends of the first sample coil When the NMR signal of the first nuclide is detected, the first, second, and third sample coils are combined to operate as one lumped constant circuit, and the resonance in the low frequency range is performed. Rejecting the second and third sample coils to block and reflect high frequencies having resonance frequencies in the high frequency range when detecting the NMR signal by frequency and detecting the NMR signal of the second nuclide. Since the first sample coil is configured to detect the NMR signal at the resonance frequency in the high frequency range while operating as a circuit, at least two nuclides are detected. From no specimen, we have become possible to provide a NMR probe as the NMR signal of the LF band and HF band can be efficiently detected.

  Also, a first sample coil composed of at least one sample coil, and a capacitive element that is connected in series to both ends of the first sample coil and forms a series resonance circuit for high frequencies in the high frequency range together with the first sample coil. Are connected in series to both ends of the first sample coil, and operate as a rejecting circuit that blocks and reflects the high frequency from the first sample coil side for high frequency in the high frequency range, For the high frequency band, the first and second sample coils of the second and third sample coils and the second and third sample coils that operate as one lumped constant circuit by combining the first sample coils Is connected in series to the connection end opposite to the connection end, and together with the first, second, and third sample coils, the high frequency in the low frequency range In contrast, a capacitor element forming a series resonance circuit, a high-frequency region high-frequency injection terminal, and a low-frequency region high-frequency injection terminal are provided, so that an LF region and HF region NMR can be obtained from a sample containing at least two nuclides. It has become possible to provide an NMR probe that can detect a signal efficiently.

Embodiments of an NMR probe according to the present invention will be described below in detail with reference to the drawings. In the present embodiment, ¹³ C nuclei and ¹ H nuclei are assumed as nuclides that give NMR signals in the LF region and the HF region. However, the present invention can be similarly applied to combinations of other nuclides.

  FIG. 2 is a diagram showing a schematic configuration of an NMR spectrometer to which the NMR probe of the present embodiment is applied.

  This NMR spectrometer includes a magnet 2 for applying a substantially uniform static magnetic field to a sample tube 1 for storing a sample, a room temperature shim 3 for correcting non-uniformity of the static magnetic field due to the magnet 2 at room temperature, and a sample tube 1. It has an NMR probe 4 for detecting an NMR signal from a stored sample, and a temperature variable (VT) device 5 for storing the sample tube 1 and the NMR probe 4 to change the temperature.

  The NMR probe 4 has one or three sample coils, and detects NMR signals in the LF region and the HF region from a sample containing at least two nuclides. The NMR probe 4 will be described in detail later.

  The NMR spectrometer includes a magnetic field correction device 6 that controls the correction of the static magnetic field by the room temperature shim 3, a computer 7 that controls the entire NMR spectrometer, the operating state of the NMR spectrometer, and the observed NMR signals. A display 8 such as an LCD for displaying the signal, a duplexer 9 that multiplexes and separates signals transmitted to and received from the NMR probe 4, and an amplifier 10 that amplifies the signal transmitted from the NMR probe 4 via the duplexer 9; A demodulation detector 11 for demodulating and detecting the NMR signal amplified by the amplifier 10, and an analog-to-digital converter (ADC) 12 for performing analog-to-digital conversion on the signal output from the demodulation detector 11. doing.

  Further, this NMR spectroscopic apparatus includes a first power amplifier 13 for power-amplifying a high frequency (RF) of a first frequency f 1 sent to the NMR probe 4 via the duplexer 9, and similarly to the NMR probe 4 for the duplexer 9. And a second power amplifier 15 for amplifying the RF of the second frequency f2 sent via the third frequency f3, and a third power amplifying the RF of the third frequency f3 sent to the NMR probe 4 via the duplexer 9 The power amplifier 16, the first power amplifier 13, the second power amplifier 15, and the third power amplifier 16 include an RF having a first frequency f 1, an RF having a second frequency f 2, and a third frequency f 3. And an oscillator 14 for supplying the RF.

Here, the first frequency f1 and the second frequency f2 correspond to the NMR signal in the LF region by ¹³ C nuclei and the NMR signal in the HF region by ¹ H nuclei. The oscillator 14 generates the RF of the first frequency f1 and the RF of the second frequency f2 based on the observation signal sent from the demodulation detector 11. The third frequency f3 corresponds to the NMR signal of the third nuclide other than the nuclide.

  FIG. 3 is a diagram showing the configuration of an NMR probe used in the NMR spectrometer of the present embodiment. FIG. 3A is a circuit diagram showing a schematic configuration of the NMR probe, and FIG. 3B is a schematic diagram for explaining the operation of the NMR probe.

  The sample coil S of the NMR probe in FIG. 3A includes a first sample coil S1-a, a second sample coil S2-a, a third sample coil S1-b, and a fourth sample coil S2-b. , Consists of four coils. Among these, as shown in FIG. 3B, the sample coils located at both ends of the four sample coils, that is, the third sample coil S1-b and the fourth sample coil S2-b, respectively, have a certain length. Assuming that the transmission line has a transmission line, the sample coil S is regarded as one lumped constant circuit (S1-a and S2-a) sandwiched between two distributed constant circuits (S1-b and S2-b). Can do.

  In such an NMR probe, both ends of the sample coil S are grounded via LF tuning capacitors C5 and C6 in series. Thereby, the sample coil S and the LF tuning capacitors C5 and C6 constitute a series resonance circuit for LF. Further, a terminal port1 for injecting RF in the LF region is connected to the left end of the sample coil S through an LF matching variable capacitor C7. Further, the LF matching variable capacitor C7 and the terminal port1 are grounded via the LF tuning capacitor C8. Thus, tuning matching is performed with respect to RF in the LF region injected from the port 1. Instead of C7, C8 may be a variable capacitor, or both C7 and C8 may be variable capacitors.

FIG. 4 shows the circuit operation in the LF region as an approximate concept. As shown in FIG. 4, since the HF tuning capacitors C1 and C2 have a small capacity, they have high impedance at the time of LF resonance, and their existence can be ignored. As a result, the circuit is approximately represented as a series resonant circuit by the sample coil S and the tuning capacitors C5 and C6, and the sample coil S (S1-a, S1-b, S2-a, S2-b) is one. While operating as a lumped constant circuit, it can resonate with respect to RF in the LF region, for example, RF in the resonance frequency region of ¹³ C nucleus.

  Next, both ends of the lumped constant circuit (S1-a and S2-a) constituting the central portion of the sample coil S are grounded via HF tuning capacitors C1, C2, and C3 in series. As a result, the sample coil S and the HF tuning capacitors C1, C2, and C3 form a series resonance circuit for HF. A terminal port2 for injecting RF in the HF region is connected to the left end of the lumped constant circuit (S1-a and S2-a) via an HF tuning capacitor C2 and an HF matching variable capacitor C4. The HF matching variable capacitor C4 is grounded via the HF tuning capacitor C3. Thus, tuning matching is performed with respect to RF in the HF region injected from the port 2. Instead of C4, C3 may be a variable capacitor, or both C3 and C4 may be variable capacitors.

  In addition, since the two distributed constant circuits (S1-b and S2-b) constituting both ends of the sample coil S are set so that the length as a transmission line is λ / 4 of HF, During HF resonance, S1-b and S2-b each function as a rejecting circuit that blocks and reflects HF. Therefore, S1-b and S2-b are constituted by lumped constant circuits (S1-a and S2-a) constituting the central portion of the sample coil S and HF tuning capacitors C1, C2, C3. It acts to be confined in the series resonant circuit.

FIG. 5 shows the circuit operation in the HF region as an approximate concept. As shown in FIG. 5, since the presence of the LF tuning capacitors C5 and C6 can be ignored by the presence of a rejecting circuit that cuts off and reflects HF, the circuit is a lumped constant circuit that forms the central portion of the sample coil S. (S1-a and S2-a) and an approximate representation as a series resonant circuit composed of only HF tuning capacitors C1, C2, and C3. As a result, this circuit operates S1-a and S2-a as a rejecting circuit that cuts off and reflects RF in the HF region, while making RF in the HF region, for example, the RF in the resonance frequency region of the ¹ H nucleus. On the other hand, it can resonate.

  As described above, the sample coil S according to the present embodiment can use the line lengths of the coils S1-b and S2-b connected to both ends thereof as a distributed constant circuit, while the coils S1-b and S2 at both ends are used. -B can be regarded as one inductance as a lumped constant circuit combined with the coils S1-a and S2-a at the center.

The sample coil S has different resonance frequencies when operating as a distributed constant circuit and a lumped constant circuit. In the present embodiment, a part of the sample coil S is operated as a distributed constant circuit, so that it corresponds to a high-frequency NMR signal by ¹ H nucleus and at the same time, the entire sample coil S is operated as a lumped constant circuit. , And ¹³ C nuclei are set to resonate with the low-frequency NMR signal.

  FIG. 6 is a diagram showing a configuration of a saddle type sample coil used for the NMR probe. 6A is a development view of the sample coil S, and FIG. 6B is a perspective view of the sample coil S. FIG.

  The sample coil S is obtained by adding two lead portions L1 and L2 to a vertical coil formed by soldering the first sample coil S1-a and the second sample coil S2-a at the connection portion 25. is there. An effective length (hereinafter referred to as the first and second lengths) excluding the length L3 of the connecting portion 25 by adding two lead portions L1 and L2 to the first and second sample coils S1-a and S2-a. Called track length.) S1 and S2 are respectively defined as follows.

S1 = L2 + Z4 + W4 + Z3 + W3
S2 = L1 + W1 + Z1 + W2 + Z2
The first, second, third, and fourth sample coils, S1-a, S1-b, S2-a, and S2-b are defined as follows, respectively.

S1-a = Z4 + W4 + Z3 + W3
S1-b = L2
S2-a = W1 + Z1 + W2 + Z2
S2-b = L1
At this time, one terminal of the HF tuning capacitor C1 is connected to the connection point between L1 and W1, and one terminal of the HF tuning capacitor C2 is connected to the connection point between L2 and Z4. The other terminal of the capacitor C1 is connected to the ground, and the other terminal of the HF tuning capacitor C2 is connected to the HF injection terminal port2 through the HF tuning matching circuit. Further, one terminal of the LF tuning capacitor C5 is connected to the tip of the lead portion L1, and one terminal of the LF tuning capacitor C6 is connected to the tip of the lead portion L2, respectively. The other terminals of the LF tuning capacitors C5 and C6 are grounded.

  In the sample coil S of the present embodiment, the first and second line lengths S1 and S2 are set to be the same or substantially the same. That is, S1 = S2 or S1≈S2. Furthermore, the line lengths of the two lead portions L1 and L2 are substantially equal to each other, and are set to lengths that resonate at λ / 4 wavelength with respect to RF in the HF region.

  For example, for the HF frequency f = 600 MHz, the two lead portions L1 and L2 are set to approximately 125 mm. Further, for example, for the frequency f = 500 MHz in the HF region, the two lead portions L1 and L2 are set to approximately 150 mm.

  Thus, one terminal of the HF tuning capacitor C1 is attached to the connection point between L1 and W1, and one terminal of the HF tuning capacitor C2 is attached to the connection point between L2 and Z4, so that Z4 + W4 + Z3 + W3 + Z2 + W2 + Z1 + W1 HF rejecting function distribution constant with characteristic impedance that cuts off / reflects HF, while the line segment becomes the HF resonance coil and the remaining leads L1 and L2 become λ / 4 wavelength resonators of HF It becomes a circuit.

  Although FIG. 6 shows a coil wound only once, two lead portions L1 and L2 can be set in the same manner when wound twice or more. FIG. 7 is a diagram showing a sample coil wound once or twice or more times. FIG. 7A shows a case where only one winding is performed, FIG. 4B shows a case where winding is performed twice, and FIG. 4C shows a case where winding is performed three times. FIGS. 7 (a) to 7 (c) are examples of series wound saddle coils, but the same applies to para wound saddle coils as shown in FIG. .

  FIG. 8 shows a case of a saddle type coil wound twice in a para winding. In this case, since the HF tuning capacitors C1 and C1 'are connected to the maximum amplitude point of HF on the left and right coils, the connection point is in the middle of the coil. However, depending on the phase of the HF, it may be necessary to shift the connection point of the HF tuning capacitors C1 and C1 'from the maximum amplitude point of the HF. The capacitances of the two HF tuning capacitors C1 and C1 ′ are set to be equal to each other when the left and right coils are equal (in the case of a balanced circuit), but generally the capacitors C1 and C1 ′ are connected. The capacity is also changed according to the position.

  Further, the present invention can be applied not only to a saddle type sample coil but also to a solenoid type sample coil. FIG. 9 shows a case where the present invention is applied to a solenoid type coil. In the figure, the sample coil 30 corresponds to S1-a and S2-a in FIG. 3, the sample coil 35 corresponds to S1-b in FIG. 3, and the sample coil 40 corresponds to S2-b in FIG. ing.

  As described above, in the NMR probe for detecting NMR signals from two nuclides, the first sample coil composed of at least one sample coil and the second and second connected in series to both ends of the first sample coil. When the NMR signal of the first nuclide is detected, the first, second, and third sample coils are combined and operated as one lumped constant circuit, When the NMR signal is detected by the resonance frequency in the frequency range and the NMR signal of the second nuclide is detected, the second and third sample coils are cut off and reflected from the high frequency having the resonance frequency in the high frequency range. Since the first sample coil is configured to detect an NMR signal at a resonance frequency in a high frequency range while operating as a rejecting circuit, at least One of the nuclide from a sample containing, it has become possible to provide a NMR probe as the NMR signal of the LF band and HF band can be efficiently detected.

  Also, a first sample coil composed of at least one sample coil, and a capacitive element that is connected in series to both ends of the first sample coil and forms a series resonance circuit for high frequencies in the high frequency range together with the first sample coil. Are connected in series to both ends of the first sample coil, and operate as a rejecting circuit that blocks and reflects the high frequency from the first sample coil side for high frequency in the high frequency range, For the high frequency band, the first and second sample coils of the second and third sample coils and the second and third sample coils that operate as one lumped constant circuit by combining the first sample coils Is connected in series to the connection end opposite to the connection end, and together with the first, second, and third sample coils, the high frequency in the low frequency range In contrast, a capacitor element forming a series resonance circuit, a high-frequency region high-frequency injection terminal, and a low-frequency region high-frequency injection terminal are provided, so that an LF region and HF region NMR can be obtained from a sample containing at least two nuclides. It has become possible to provide an NMR probe that can detect a signal efficiently.

  It can be used for a probe for NMR.

It is a figure which shows the conventional probe for double tuning NMR. It is a figure which shows the structure of the NMR spectrometer concerning this invention. It is a figure which shows the structure of the NMR probe concerning this invention. It is a figure which shows the operation | movement concept in LF area | region of the NMR probe concerning this invention. It is a figure which shows the operation | movement concept in the HF area | region of the NMR probe concerning this invention. It is a figure which shows an example of the saddle type coil used for the NMR probe of this invention. It is a figure which shows an example of the saddle type coil used for the NMR probe of this invention. It is a figure which shows an example of the saddle type coil used for the NMR probe of this invention. It is a figure which shows an example of the solenoid type coil used for the NMR probe of this invention.

Explanation of symbols

1: Sample tube, 2: Magnet, 3: Room temperature shim, 4: NMR probe, 5: Variable temperature (VT) device, 6: Magnetic field correction device, 7: Computer, 8: Display, 9: Duplexer, 10: Amplifier: 11: Demodulation detector, 12: Analog to digital converter (ADC), 13: First power amplifier, 14: Oscillator, 15: Second power amplifier, 16: Third power amplifier, 25: Connection Part: 30: sample coil, 35: sample coil, 40: sample coil, 101: HF range signal detector, 102: LF range signal detector, C1: HF tuning capacitor, C2: HF tuning capacitor, C3: HF Tuning capacitor, C4: HF matching variable capacitor, C5: LF tuning capacitor, C6: LF tuning capacitor, C7: LF matching variable capacitor, C8: LF tuning capacitor Sensor, C100: variable capacitor, C101: capacitor, C111: variable capacitor, C112: variable capacitor, L1: lead part, L2: lead part, L100: sample coil, L101: sample coil, S: sample coil, S1 : First line length, S2: second line length, S1-a: first sample coil, S1-b: third sample coil, S2-a: second sample coil, S2-b: first 4 sample coils

Claims (8)

In an NMR probe that detects NMR signals from two nuclides,
A first sample coil comprising at least one sample coil; and second and third sample coils connected in series at both ends of the first sample coil;
When detecting the NMR signal of the first nuclide, the first, second and third sample coils are combined and operated as one lumped constant circuit, while the NMR signal is generated at the resonance frequency in the low frequency range. Detect
When detecting the NMR signal of the second nuclide, the second and third sample coils are operated as a rejecting circuit that cuts off and reflects a high frequency having a resonance frequency in a high frequency range. An NMR probe configured to detect an NMR signal at a resonance frequency in a high frequency range by using the sample coil. 2. The NMR probe according to claim 1, wherein the second and third sample coils are high-frequency [lambda] / 4 resonators having a resonance frequency in a high frequency range. 3. The NMR probe according to claim 1, wherein the first nuclide is ² D, ¹³ C, ¹⁵ N, ³² P, and a low γ nuclide. 4. The NMR probe according to claim 1, wherein the second nuclide is ¹ H, ¹⁹ F, and ³¹ P. 5. A first sample coil comprising at least one sample coil;
A capacitive element that is connected in series to both ends of the first sample coil and that forms a series resonant circuit for high frequencies in the high frequency range together with the first sample coil;
It is connected in series to both ends of the first sample coil, and operates as a rejecting circuit that blocks and reflects high frequencies from the first sample coil side for high frequencies in the high frequency range, For high frequencies, the second and third sample coils that operate as one lumped constant circuit by combining the first sample coils;
The second and third sample coils are connected in series to the connection end opposite to the connection end of the first sample coil, and together with the first, second, and third sample coils, A capacitive element forming a series resonant circuit for high frequencies;
An NMR probe comprising a high frequency injection terminal in a high frequency range and a high frequency injection terminal in a low frequency range. 6. The NMR probe according to claim 5, wherein the second and third sample coils are high-frequency λ / 4 resonators having a resonance frequency in a high frequency range. It said first ^{nuclide, 2 D, 13 C, 15} N, 32 P, and claims 5 or 6 NMR probe according characterized in that it is a low γ nuclide. 8. The NMR probe according to claim 5, wherein the second nuclide is ¹ H, ¹⁹ F, and ³¹ P. 9.

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