JPS6193940A - Nuclear magnetic resonator - Google Patents

Abstract

PURPOSE:To remove the unnecessary peak of high intensity by calculating power spectral data from the nuclear magnetic resonance spectral data obtd. from a transmitting and receiving coil and supplying the frequency corresponding to the data position of the max. intensity to a decoupling coil. CONSTITUTION:A sample tube 2 is disposed in the static magnetic field generated by a magnet 1. The transmitting and receiving coil 3 and the decoupling coil 4 are disposed in proximity to the tube 2. An oscillator 5 generates the high frequency to be supplied to the coil 3 and a variable frequency oscillator 6 generates the high frequency to be supplied to the coil 4. The nuclear magnetic resonance spectral data obtd. from the coil 3 is fed to a data processing unit 3, by which the powder spectral data is calculated in accordance with the real number component and imaginary number component. The frequency corresponding to the data position of the max. intensity in the power spectral data is determined and the oscillation frequency of the oscillator 6 is set at said frequency. The unnecessary peak of the large intensity occurring from water or solvent, etc. and appearing in the nuclear magnetic resonance spectrum is thus removed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a nuclear magnetic resonance apparatus (NMR apparatus), and in particular to a nuclear magnetic resonance apparatus (NMR apparatus).
The present invention relates to an NMR apparatus that can automatically perform measurements by removing unnecessary peaks of high intensity caused by water, solvent, etc. that appear in an MR spectrum.

[Prior art] In an NMR apparatus, a high-frequency pulsed magnetic field is irradiated onto a sample to be measured placed in a static magnetic field, and a free induction decay signal @ (FID signal) derived from the irradiation of the high-frequency pulsed magnetic field is detected. Then, this FID signal, which is a signal in the time domain, is Fourier transformed into the frequency domain to obtain an NMR spectrum as shown in FIG. 4(d), for example. However, when observing hydrogen nuclei (protons) in an aqueous solution sample, a peak from the solvent (water) in which the sample was dissolved appears in the spectrum, and because the amount is overwhelmingly large, the peak intensity is extremely low. It becomes something big. Since the gain of the apparatus is set so as not to saturate this high-intensity solvent peak, a sufficient signal-to-noise ratio cannot be obtained for the signal of the target microm sample component.

Therefore, in order to eliminate this inconvenience, only the protons of the solvent are saturated in advance by irradiating the sample with a high-frequency magnetic field of a frequency corresponding to the peak of the solvent before sampling the FTD signal. The so-called homogate decoupling method (HGD method) is often used to suppress this.

[Problems to be Solved by the Invention] In order to implement this method, Nikoro first obtains the NMR spectrum of the sample using a normal measurement method other than the HGD method.
The operator confirms the frequency of the solvent peak from the position of the solvent peak in the spectrum, then sets the oscillation frequency of the decoupling high-frequency oscillator to the frequency of the solvent peak, and then starts measurement using the HGD method. , it is necessary to go through complicated steps such as
Not only did this require skill, but it was also inevitable that the '1At1 constant time would become long.

The present invention has been made in view of this point, and it is an object of the present invention to provide an NMR apparatus that can automatically set the oscillation frequency of a high-frequency oscillator for decoupling.

[Means for Solving the Problems] In order to achieve this object, the present invention provides a transmitting/receiving coil and a decoupling coil placed near a sample to be measured placed in a static magnetic field, and an observation coil connected to the transmitting/receiving coil. means for supplying a high frequency pulse for decoupling, a variable frequency oscillator for generating a high frequency decoupling wave to be supplied to the decoupling coil; In an NMR apparatus comprising means for detecting a free induction attenuation signal and means for Fourier transforming the free induction attenuation signal to obtain an NMR spectrum, based on the real component and imaginary component of the obtained NMR spectrum data, calculation means for obtaining power spectrum data; maximum value detection means for obtaining the maximum intensity data position in the power spectrum data;
The present invention is characterized in that a means for determining a frequency corresponding to the data based on the determined data position is provided, and the oscillation frequency of the variable frequency oscillator is set to the frequency. Hereinafter, one embodiment of the present invention will be explained in detail using the drawings.

[Example] FIG. 1 is a block diagram showing an example of an NMR apparatus implementing the present invention. In the figure, 1 is a magnet that generates a static magnetic field,
2 is a sample tube placed in a static magnetic field, 3.4 is a transmitting/receiving coil and a decoupling coil placed close to the sample tube, 5 is an oscillator that generates a high frequency to be supplied to the transmitting/receiving coil 3, and 6 is a decoupling coil. This is a variable frequency oscillator that generates high frequency waves to be supplied to the ring coil 4. The high frequency generated by the oscillator 5 is sent to the transmitting/receiving coil 3 via the gate 7 and the amplifier 8, and is irradiated onto the sample as a high frequency pulsed magnetic field. A resonance signal induced in the sample coil 3 after irradiation with this high-frequency pulsed magnetic field is extracted via an amplifier 9 and a gate 10 and sent to a demodulator 11. The free induction decay signal (FID signal) obtained by demodulation is sent to the A-D converter 12.
The data is sent to the data processing device 13 via.

The data processing device 13 includes an FID signal storage section 14, a Fourier transform processing section 15, and a memory 16 attached thereto;
It includes a power spectrum calculation section 17, a memory 18 attached thereto, a maximum value detection section 19, and a frequency calculation section 20, and the oscillation frequency of the oscillator 6 is set to the frequency determined by the calculation section 20. Note that 21 and 22 are gates and amplifiers inserted between the oscillator 6 and the coil 4, and 23 is a timing circuit that controls the operations of the gates 7, 10, and 21 and the A/D converter 12.

In the configuration as described above, measurements proceed according to the procedure shown in FIG. That is, (1) The oscillator 6 is not operated, the oscillation/stationary wave number of the oscillator 5 is set to the resonant frequency of protons, and a temporary measurement is performed using a normal measurement method other than the HGD method. In this case, the gate 7 is turned on at the timing shown in FIG. 3(a), and a high-frequency pulsed magnetic field is irradiated onto the sample. ) After l, the gate 10 is turned on at the timing shown in FIG. 3(b), and the FID
A signal is extracted for that period. The extracted FID signal is sampled by the A-D converter 12 which operates for the same period as the gate 10, and is stored in the FID signal storage section 14.

(2) This FID signal is subjected to Fourier transform in the Fourier transform section 15, thereby converting it into frequency domain spectral data. Spectral data is obtained in the form of complex numbers x+iY and stored in memory 16. If the real part of this spectral data is extracted and displayed, a spectrum with an absorption waveform as shown in FIG. 4(a), for example, is obtained, and if the imaginary part is extracted and displayed, a spectrum with a dispersion waveform as shown in FIG. 4(b), for example, is obtained. is obtained. In these spectra there are
Naturally, there is a large peak Ps due to the solvent.

(3) In performance W part 17, %24- for all data
``y'2-'' to obtain power spectrum data. The power spectrum data is stored in the memory 18. As shown in FIG. -Although the resolution is lower, it has the characteristic that it is not affected by phase shift.

(4) The maximum value detection unit 19 reads out all the power spectrum data and compares the intensities to detect the peak Psi of the solvent having the highest intensity.

(The frequency calculation circuit 20 calculates the solvent peak frequency fs from the position (data number) of the highest intensity power spectrum data detected in (4). This frequency calculation is performed using the reference frequency (oscillator 5 oscillation frequency)
This can be easily done from f to the frequency change per data.

(6) The oscillation frequency of the oscillator 6 is the frequency fs1 calculated in (5). : Set.

(7) Perform the main measurement using the HGD method. In this case, the operation of the observation side channel is exactly the same as the temporary measurement, and the gate 7 is turned on at the timing shown in FIG. b
), the A-D converter 1 is turned ON and the FID signal is taken out during that period, and operates for the same period as the gate 10.
2 and stored in the FID signal storage section 14.

The difference from the preliminary measurement is that the gate 21 is turned on at the timing shown in FIG. 3(C) prior to the irradiation of the high-frequency pulse, and during that period a high-frequency magnetic field with a frequency fs is irradiated from the decoupling coil 4 to the sample. be.

(8) The FID signal subjected to IH in the main measurement is subjected to Fourier transform in the Fourier transform section 15, thereby converting it into frequency domain spectral data. In the resulting spectrum, as shown in FIG. 4(d), the peak of the solvent is suppressed by the high-frequency magnetic field irradiation with the frequency fs.

In the above embodiment, the case where the HG'D method is used has been described, but there are various so-called homodecoupling methods other than the HGD method that decouple the same nucleus as the observation nucleus, and the present invention applies to all of them. can be applied.

[Effects of the Invention] As described in detail above, according to the present invention, an NMR apparatus that can automatically set the oscillation frequency of a decoupling oscillator is realized.

Furthermore, in the present invention, a power spectrum is determined based on the spectral data obtained in the preliminary measurement, and a solvent peak is determined based on the power spectrum, so that the preliminary measurement can be performed without considering phase adjustment at all.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of an NMR apparatus in which the present invention was applied, FIG. 2 is a diagram showing the measurement procedure performed in the embodiment of FIG. 1, and FIG. A timing diagram for explaining the operation of the example, and FIG. 4 is a diagram showing a spectrum obtained in the course of measurement. 1:! a stone 2: sample tube 3: transmitting/receiving coil 4: decabbing coil 5.6: oscillator 7.10.21: gate 11: demodulator 12: A-D converter 13: data processing device 14: FID signal storage section 15 :Fourier transform processing unit 16.18:Memory 17:Power spectrum calculation unit

Claims (1)

[Claims] A transmitting/receiving coil and a decoupling coil disposed near a measurement sample placed in a static magnetic field, a means for supplying observation high frequency pulses to the transmitting/receiving coil, and a means for supplying observation high frequency pulses to the decoupling coil. a variable frequency oscillator for generating a high frequency wave for decoupling; a means for detecting a free induction damping signal derived based on the high frequency pulsed magnetic field irradiation via the transmitter/receiver coil; A nuclear magnetic resonance apparatus comprising: means for obtaining a magnetic resonance spectrum, a calculation means for obtaining power spectrum data based on real and imaginary components of the obtained nuclear magnetic resonance spectrum data; Providing maximum value detection means for determining the data position of maximum intensity, and means for determining the frequency corresponding to the data based on the determined data position,
A nuclear magnetic resonance apparatus characterized in that the oscillation frequency of the variable frequency oscillator is set to the above frequency.