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NMR Spectroscopy

NMR Spectroscopy. Prepared by: Joy Lapinig Karen Mae Laid Rhea Villacampa. Introduction.

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NMR Spectroscopy

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  1. NMR Spectroscopy Prepared by: Joy Lapinig Karen Mae Laid Rhea Villacampa

  2. Introduction There are two general types of NMR instrument; continuous wave and Fourier transform. Early experiments were conducted with continuous wave (C.W.) instruments, and in 1970 the first Fourier transform (F.T.) instruments became available. This type now dominates the market.

  3. Continuous Wave NMR Instruments Continuous wave NMR spectrometers are similar in principle to optical spectrometers. The sample is held in a strong magnetic field, and the frequency of the source is slowly scanned (in some instruments, the source frequency is held constant, and the field is scanned).

  4. Fourier transform NMR Instruments • The magnitude of the energy changes involved in NMR spectroscopy are small. This means that sensitivity is a major limitation. One way to increase sensitivity would be to record many spectra, and then add them together; because noise is random, it adds as the square root of the number of spectra recorded. For example, if one hundred spectra of a compound were recorded and summed, then the noise would increase by a factor of ten, but the signal would increase in magnitude by a factor of one hundred - giving a large increase in sensitivity. However, if this is done using a continuous wave instrument, the time needed to collect the spectra is very large (one scan takes two to eight minutes). • In FT-NMR, all frequencies in a spectrum are irradiated simultaneously with a radio frequency pulse. Following the pulse, the nuclei return to thermal equilibrium. A time domain emission signal is recorded by the instrument as the nuclei relax. A frequency domain spectrum is obtained by Fourier transformation.

  5. HISTORY Felix Bloch and Edward Mills Purcell(1946) -1st to described independently the nuclear magnetic resonance (NMR). -nobel price in physics in 1952 -then the NMR develop as a technique of analytical chemistry and biochemistry. Richard R. Ernst(1991) -Ft-NMR works by irradiating the sample,held in static external magnetic field .

  6. Richard R.Ernst and Kurt Wuthrich(2002) -developed 2 dimensional and multidimensional FT-NMR into a powerful technique. Raymond Andrew -pioneer the development of high –resolution solid state NMR. Alex Pines and John Waugh Revolutionized the area w/ the introduction of the cross polarization technique

  7. Uses of Nuclear Magnetic Resonance • Magnetic resonance imaging for medical diagnoses and used in chemical studies, notably in NMR spectroscopy. • Extremely useful for analyzing sample nondestructively. • Used as data acquisition in the petroleum industry for petroleum and natural gas exploration and recovery.

  8. Parts of the Magnet • Reflective Myler • Vacuum • N2 Reservoir • He Reservoir • Super conducting Solenoid

  9. HOW NMR WORKS

  10. Steps in Preparing Samples • Use the Correct Quantity of Material • Remove all solid particles • Make samples to the Correct Depth • Use Deuterated Solvents • Use clean Tubes and Caps • Label Your Samples • Use an Internal reference • Degassing Samples

  11. THANK YOU AND GOD BLESS YOU ALL!

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