JPS6129750A - Nuclear magnetic resonance device - Google Patents

Abstract

PURPOSE:To obtain an inexpensive device by detecting the decoupling of a heavy hydrogen nucleus in a sample and the detection of a heavy hydrogen nuclear resonance signal for magnetic field locking of an external sample on a time-division basis. CONSTITUTION:A resonance frequency signal generated by a resonance frequency source 2 for a carbon nucleus is passed through a gate circuit 6 and amplified 9, and applied to a probe 13 to activate the resonance of the carbon nucleus. Further, the output signal of a decoupling frequency source 3 for a hydrogen nucleus is amplified 10 and applied to the probe 13, thereby decoupling the hydrogen nucleus. The resonance signal of the carbon nucleus obtained by the probe 13 is amplified 15 and detected 18, and its detection signal is Fourier-transformed 21 to obtain the spectrum of the carbon nucleus. The output signal of a magnetic field locking system frequency source 5 for the heavy hydrogen nucleus, on the other hand, is passed through a gate circuit 8, switch 11, probe 13 and amplified 16, detected 19 and further amplified 20, and fed back 14. When the switch 11 is operated, the output signal of the frequency source 4 is applied to the heavy hydrogen nucleus of a measured sample through a gate 7 and the switch 11 to detect the resonance signal of the heavy hydrogen nucleus of the external sample.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a nuclear magnetic resonance apparatus.

[Background of the invention]

General Fourier transform nuclear magnetic resonance apparatus (FT/NMR)
The method places the measurement sample in a uniform DC magnetic field, applies a high-frequency pulse corresponding to the resonant frequency of the measurement nucleus to it, simultaneously excites the resonance of the entire measurement nucleus, and receives the resonance signal in the desired frequency band. After receiving the signal, it is converted by an A/D converter and taken into the data processing device at a predetermined period, and the frequency spectrum of the measurement sample is obtained by Fourier transformation.

In such devices, there are various requirements regarding measurements. First, a uniform DC magnetic field must be correlated with a frequency source that excites resonance, a frequency source that decouples, etc. To this end, it has been conventional practice to detect the resonance signal of deuterium nuclei in the solvent in the sample and feed it back to the DC magnetic field to stabilize the DC magnetic field. Looking at this stabilization control in more detail, there are cases in which the resonance signal of deuterium nuclei in the measurement sample is used, and there are cases in which the resonance signal of deuterium nuclei in the external sample is used. In the former case, it is possible to detect the magnetic field intensity at exactly the same position as the measurement sample, but there is a drawback that a solvated deuterated sample must be used. On the other hand, in the latter case, no restrictions are required on the measurement sample, but complete magnetic field stabilization cannot be achieved because the magnetic field strength is detected at a position different from that of the measurement sample, and the magnetic field uniformity at the measurement sample position cannot be adjusted. (adjustment of resolution) cannot be carried out.

On the other hand, when a measurement nucleus is spin-coupled with another nucleus, the spectral peaks become separated and complicated, which can reduce sensitivity. Therefore, in order to avoid this, it is necessary to apply high frequency power at the resonance frequency of the other nucleus in order to decouple the spin coupling with the other nucleus. For example, when measuring carbon nuclei, high-frequency power with the resonant frequency band of hydrogen nuclei is injected into the sample, and the spin coupling of hydrogen nuclei is decoupled to obtain a simple and highly sensitive spectrum of carbon nuclei.
- Therefore, such conventional equipment is extremely inconvenient for chemical structure analysis of deuterated samples. In other words, in many ordinary samples, the chemical structure is determined by carbon and hydrogen nuclei, so by obtaining information on chemical shifts, spin bonds, etc. from the spectrum of the carbon nucleus and the spectrum of the hydrogen nucleus, in which the hydrogen nucleus is decoupled. Attribution of spectra becomes possible. However, for the deuterated sample mentioned above, a carbon nuclear spectrum and a deuterium nuclear spectrum with decoupled deuterium nuclei are required. For this purpose, a frequency source is used to detect the resonance signal of the deuterium nuclei in the solvent of the measurement sample.

The disadvantage is that the gate circuit, irradiation circuit, receiver, etc. are duplicated for deuterium nuclei and for non-deuterium nuclei, making them extremely expensive.

[Purpose of the invention]

An object of the present invention is to provide a nuclear magnetic resonance apparatus that can obtain a spectrum of a deuterated sample using a single magnetic field lock system.

[Summary of the invention]

In the present invention, if the resonant nucleus for locking the magnetic field is a deuterium nucleus, and the external sample is also a deuterium nucleus, the frequency source, gate circuit, irradiation circuit, and receiver for magnetic field lengthening can be a single system for the deuterium nucleus. When measuring carbon nuclei by decoupling the deuterium nuclei in the measurement sample, switching the magnetic field lock to the resonance signal of the external sample allows decoupling of the deuterium nuclei and external locking of the deuterium nuclei. The system is configured to separate the system in a time-sharing manner.

[Embodiments of the invention]

The embodiment of the present invention shown in FIG. 1 will be described below.

In FIG. 1, the master clock generated from the master clock generator 1 is a carbon nucleus resonance frequency source 2, a hydrogen nucleus decoupled frequency source 3, a deuterium nucleus decoupled frequency source 4, and a deuterium nucleus magnetic field lock system frequency. power source 5.

A resonance frequency signal generated from a carbon nucleus resonance frequency source 2 is converted into a pulse by a gate circuit 6, and then amplified by a high frequency power amplifier 9. After that, probe 13I/c is applied to excite the resonance of the carbon nucleus. Further, the output signal of the hydrogen nuclear decoupled frequency source 3 is amplified by the high frequency power amplifier 10 and applied to the prologue 13. Hydrogen nuclei are decoupled due to the bending. The carbon nucleus resonance signal obtained by the probe 13 is amplified by the high frequency amplifier 15 and then sent to the detection circuit 1B.
The wave is detected by The detected signal is then taken into the data processing device 21 and Fourier transformed there.

This provides a spectrum of carbon nuclei.

On the other hand, the output signal of the frequency source 5 of the deuterium nuclear magnetic field lock system is converted into a pulse by the gate circuit 8 and then applied to the prologue 13 via the switch 11. This excites the resonance of the deuterium nucleus of the solvent of the measurement sample. This resonance signal is amplified by the high frequency amplifier 16, detected by the detection circuit 19, further DC amplified by the feedback amplifier 20, and fed to the feedback coil 14. The strength of the DC magnetic field of The magnetic field locking system detects the resonance signal of the deuterium nucleus of the external sample via the switch 11.

The control circuit 17 turns on and off the gate circuit 7.8 and the amplifier 16 as shown in the time chart of FIG.

2(a) shows the irradiation pulse waveform of the magnetic field lock system output from the gate circuit 8, and FIG. 2(b) shows the irradiation pulse waveform of the magnetic field lock system output from the gate circuit 8.
is the gate signal of the amplifier 16 when there is no decoupling of the deuterium nucleus in the state shown in the figure! 5. When ON, the amplifier 16 operates and receives the resonance signal of the deuterium nucleus. (C) of the same figure shows the irradiation pulse of the deuterium nuclear decoupling output from the gate circuit 7 when the switch 11 is turned off and the state is opposite to that shown in the figure, and (d) of the same figure shows the irradiation pulse of the deuterium nucleus decoupled from the amplifier 16 at that time. This is the gate signal. In this case, Fig. 2 (c
) The power of the p-decoupling can also be varied by changing the pulse width of the decoupled irradiation of the deuterium nucleus, which is shown by K.

As described above, according to this embodiment, the magnetic field lock system requires only one system of deuterium nuclei in the conventional device, and a carbon nuclear spectrum in which the deuterium nuclei are decoupled can be easily obtained.

〔Effect of the invention〕

As is clear from Onoue's explanation, the present invention has excellent effects such as being able to obtain the spectrum of a deuterated sample using only one magnetic field locking system and making it possible to construct the apparatus at low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation of the embodiment.

Claims (1)

[Claims] 1. In a nuclear magnetic resonance apparatus in which resonance signals of deuterium nuclei used for magnetic field lock are obtained from two locations, a measurement sample and an external sample, a frequency signal that decouples deuterium nuclei and deuterium from the external sample are used. Nuclear magnetism characterized by being equipped with a switch for switching between high frequency signals and high frequency signals for obtaining nuclear resonance signals, and detecting the decoupling of deuterium nuclei in the sample and the deuterium nuclear resonance signals for magnetic field locking of the external sample in a time-sharing manner. Resonator. 2. Resonant excitation of deuterium nuclei in the external data and detection of resonance signals are performed in a time-sharing manner, and the deuterium nuclei in the measurement sample are decoupled in synchronization with this cycle, as described in claim 1. nuclear magnetic resonance apparatus. 3. The nuclear magnetic resonance apparatus according to claim 1, wherein the decoupling power is varied by varying the irradiation time of the high-frequency signal that decouples the deuterium nuclei of the measurement material.