NMR spectroscopy (Pharmaceutical analysis)

Explaining all the difficult concepts with precise and accurate points, 3D models, animations and smart art graphics.
Principle
The NMR phenomenon
Theory
Precessional frequency (ν)
Chemical shift
Spin-spin interactions
Interpretation of NMR
Chemical shift (δ)
Multiplicity of the signal
Coupling constant
Instrumentation
Fourier NMR
Continuous wave NMR
Applications
Identification testing
Assay of drugs

1. NMR SPECTROSCOPY Assigned By: Miss Shehla Presented By: Fatima- tu -Zahra Roll no:1427

2. CONTENTS

3. INTRODUCTION

4. NMR PHENOMENON A:The Spinning Nucleus

5. B:Effect of external field

6. C:GYROSCOPIC Precessional movement

7. C:GYROSCOPIC Precessional movement

8.  the  gyromagnetic ratio  of a particle or system is the ratio of its magnetic moment to its angular momentum

9. D:The Energy Transitions :

10. THEORY A:SPIN QUANTUM NUMBER

11. Mass Number Atomic Number Spin Quantum no. odd Odd or even I=1/2 even even even odd I=1,2,3….

12. B:CHEMICAL SHIFT The  chemical shift  in absolute terms is defined by the frequency of the resonance expressed with reference to a standard compound which is  defined  to be at 0 ppm . The scale is made more manageable by expressing it in parts per million ( ppm ) and is  indepedent  of the spectrometer frequency. 

13. C:SPIN-SPIN COUPLING

14. `

15. MAGNET

16. PROBE

17. MR Electronics MR electronics consists of a subsystems for controlling the MR transceiver, magnetic field gradients, field frequency lock, spinner speed, temperature of the sample (VT), and an interface to a computer for receiving controlling instructions and to transmit the digitized data.

18. Magnetic field gradients Magnetic field gradients are controlled by an independent subsystem. Magnetic field gradients are generated by passing current through coils of appropriate geometry. Static magnetic field gradients are used for shimming. In addition pulsed magnetic field gradients can be produced based on the instructions in the pulse program.

19. MR transceiver The MR transceiver contains two major subsystems: The transmitter and the receiver subsystems Transmitter subsystem: It consists of the RF synthesizers and amplifiers. This subsystem is responsible for generating pulse sequences containing RF pulses of specified frequency, amplitude, phase, shape and duration at specified times. Multiple RF synthesizers are required because many MR experiments require simultaneous application of RF pulses of different frequencies. RF switch is responsible for coupling either the Transmitter or the Receiver subsystem to the probe. This ensures that the sensitive receiver subsystem is not overloaded with the high powered RF signal generated by the transmitter system. Also, the receiver is 'blanked' during the transmission and for a short duration afterward. Receiver subsystem: This consists of the components: Preamplifier, Amplifier, Mixer and the Analog-to-Digital converter (ADC). The Mixer is used to subtract a reference frequency of specified phase from the observed signal, resulting a signal of lower frequency that can be easily digitized.

20. MR transceiver Field frequency lock The field frequency lock consists of a negative feedback loop that keeps the magnetic field constant. The superconducting magnets that are commonly used in high resolution NMR spectrometers usually have a drift of a few ppb per day (ppb = parts per billion of the total magnetic field). Many high resolution multidimensional NMR experiments often require more than 1 day of measurement. In order to the ensure that the magnetic field at the sample stays constant, during this time, an additional small magnetic field is created by passing current through a loop of appropriate shape to compensate for the change in magnetic field due to the main (superconducting) magnet.

21. CW-NMR In its first few decades, nuclear magnetic resonance spectrometers used a technique known as  continuous-wave  spectroscopy (CW spectroscopy). This more typically involved using a fixed frequency source and varying the current (and hence magnetic field) in an  electromagnet  to observe the resonant absorption signals. Require only water-cooled  electromagnets instead of the liquid-He-cooled superconducting magnets found in higher-field FT-NMR spectrometers. A cw -NMR spectrometer consists of a control console, magnet, and two orthogonal coils of wire that serve as antennas for radiofrequency (RF) radiation. One  coil is attached to an RF generator and serves as a transmitter. The other coil is the RF pick-up coil and is attached to the detection electronics. Since the two coils are orthogonal, the pick-up coil cannot directly recieve any radiation from the generator coil. When a nucleus absorbs RF radiation, it can become reoriented due to its normal movement in solution and re-emit the RF radiation is a direction that can be recieved by the pick-up coil. This orthogonal coil arrangement greatly increases the sensitivity of NMR spectroscopy, similar to optical fluorescence. Spectra are obtained by scanning the magnet and recording the pick-up coil signal on paper at the control console.

22. FT-NMR Most applications of NMR involve full NMR spectra, that is, the intensity of the NMR signal as a function of frequency. Early attempts to acquire the NMR spectrum more efficiently than simple CW methods involved illuminating the target simultaneously with more than one frequency. A revolution in NMR occurred when short pulses of radio-frequency radiation began to be used—centered at the middle of the NMR spectrum. In simple terms, a short pulse of a given "carrier" frequency "contains" a range of frequencies centered about the  carrier frequency , with the range of excitation ( bandwidth ) being inversely proportional to the pulse duration, i.e. the  Fourier transform  of a short pulse contains contributions from all the frequencies in the neighborhood of the principal frequency. X VVVVVVVVVVVVVVThe restricted range of the NMR frequencies made it relatively easy to use short (millisecond to microsecond) radio frequency pulses to excite the entire NMR spectrum. [ citation needed ] Applying such a pulse to a set of nuclear spins simultaneously excites all the single-quantum NMR transitions. In terms of the net magnetization vector, this corresponds to tilting the magnetization vector away from its equilibrium position (aligned along the external magnetic field). The out-of-equilibrium magnetization vector precesses about the external magnetic field vector at the NMR frequency of the spins. This oscillating magnetization vector  induces  a current in a nearby pickup coil, creating an electrical signal oscillating at the NMR frequency. This signal is known as the  free induction decay  (FID), and it contains the vector sum of the NMR responses from all the excited spins

23. APPLICATIONS 1:Medicine Medical MRI Proton NMR and carbon-13 NMR Biochemical information can also be obtained from living tissue (e.g. human  brain   tumors ) with the technique known as  in vivo magnetic resonance spectroscopy  or  chemical shift  NMR Microscopy. As one of the two major spectroscopic techniques used in  metabolomics , NMR is used to generate metabolic fingerprints from biological fluids to obtain information about disease states or toxic insults .

24. APPLICATIONS 2: Chemistry S tructure of compounds: It can be a very selective technique, distinguishing among many atoms within a molecule or collection of molecules of the same type but which differ only in terms of their local chemical environment. I dentify known and novel compounds : is usually required by scientific journals for identity confirmation of synthesized new compounds.  NMR), since its natural abundance is nearly 100%; isotope enrichment is required for most other elements. S tructural dynamics: such as ring-flipping in  cyclohexane ; At low enough temperatures, a distinction can be made between the axial and equatorial hydrogens in cyclohexane . Purity determination (w/w NMR )

25. APPLICATIONS Non-destructive testing Data acquisition in the petroleum industry Quantum computing Process control