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FT- NMR
FT-NMR uses Fourier transforms to convert time domain signals from nuclear magnetic resonance into frequency domain spectra. The sample is placed in a strong magnet and exposed to pulses of radio frequency radiation, producing a free induction decay signal that is recorded over time. This time domain signal is then digitized and analyzed using a Fourier transform program on a computer to produce the frequency domain NMR spectrum. FT-NMR provides higher sensitivity than continuous wave NMR, allowing analysis of smaller sample sizes.
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Presentation by Anjali, a first-year M.Pharm student from the Department of Pharmacy Practice at Grace College of Pharmacy.
Definition and purpose of Fourier Transform, breaking down complex waveforms and converting time domain to frequency domain.
Description of FTNMR, where samples are irradiated with pulses to record free induction decay signal. Obtaining frequency-domain spectrum using Fourier Transform.
Key components of FT-NMR, including stable magnets, transmitter/receiver coils, and crystal controlled frequency synthesizer.
The amplification and detection of nuclear signals, resulting in low frequency time-domain signal for analysis using Fourier Transform and software.
FT-NMR's increased sensitivity, faster measurement, ability to work with small sample sizes, and improved spectra for diluted compounds.
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FT- NMR
- 1. PRESENTED BY, Anjali.c I yearm.pharm Dept. Of pharmacy practice Grace college of pharmacy
- 2. It isthe mathematical operation in which the complex waveform can be broken-down into simple mathematical operations. It is the mathematical operation required to convert a time domain spectrum to frequency domain spectrum (or vice versa).
- 3. FTNMR orpulse NMR, the sample is irradiated periodically with brief, highly intense pulses of radio- frequency radiation, following which the free induction decay signal - a characteristic radio- frequency emission signal stimulated by the irradiation – is recorded as a function of time. The frequency- domain spectrum can be obtained by a Fourier transform employing a digital computer
- 6. The centralcomponent of the instrument is a highly stable magnet in which the sample is placed. The sample is surrounded by the transmitter/receiver coil. A crystal controlled frequency synthesizer having an output frequency of Vc - produces radio-frequency radiation. This signal passes into a pulse switch and power amplifier, which creates an - intense and reproducible pulse of RF current in the transmitter coil. Resulting signal is picked up by the same coil which now serves a as - receiver.
- 7. The signalis then amplified and transmitted to a phase sensitive detector. The detector circuitry produced the difference between the nuclear signals Vn and the crystal oscillator output Vc which leads to the low frequency time-domain signal . This signal is digitalized and collected in the memory of the computer for analysis by a Fourier transform program and other data analysis software. The output from this program is plotted giving a frequency domain spectrum.
- 8. FT-NMR ismore sensitive and can measure weaker signals. The pulsed FT-NMR is much faster (seconds instead of min) as compared to continuous wave NMR. FT-NMR can be obtained with less than 0.5 mg of compound. This is important in the biological chemistry, where only μg quantities of the material may be available. The FT method also gives improved spectra for sparingly soluble compounds. Pulsed FT-NMR is therefore especially suitable for the examination of nuclei that are magnetic or very dilute samples.