NMR: Difference between revisions
From Pumping Station One
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* C-13 NMR - NMR performed with a Carbon-13 probe. | * C-13 NMR - NMR performed with a Carbon-13 probe. | ||
* TMS - Tetramethylsilane Si(CH3)4 - A colorless liquid commonly used as a reference standard. The peak of TMS is used to set a reference of where zero is. | * TMS - Tetramethylsilane Si(CH3)4 - A colorless liquid commonly used as a reference standard. The peak of TMS is used to set a reference of where zero is. | ||
* PPM - The unit "chemical shift" is | * Chemical Shift (PPM) - The unit of the x-axis is "chemical shift" in ppm. PPM is simply the chemical shift in Hz divided by the NMR frequency and multiplied by 1,000,000. This standardizes the position of the resulting peaks across instruments with different field strengths, so something like water or vinegar will always shows peaks in the same ppm values regardless of the capabilities of an instrument. This corresponds to the shift from the reference frequency from 0ppm. | ||
* Upfield / Shielded / Lower Energy - Peaks occurring closer to 0ppm (near the right side of x-axis). They require less energy to bring them into resonance. | * Upfield / Shielded / Lower Energy - Peaks occurring closer to 0ppm (near the right side of x-axis). They require less energy to bring them into resonance. | ||
* Downfield / Deshielded / Higher Energy - Peaks further left on the x-axis (away from 0ppm), require more energy to bring them into resonance. | * Downfield / Deshielded / Higher Energy - Peaks further left on the x-axis (away from 0ppm), require more energy to bring them into resonance. | ||
* Gyromagnetic Ratio or Gamma γ - | * Gyromagnetic Ratio or Gamma γ - This is a fundamental property of a given isotope. The higher this number, the more signal it produces in NMR. For Hydrogen-1 this is 42.58MHZ / Tesla. Hydrogen-1 has one of the higher Gyromagnetic Ratios and the presence of hydrogen in just about everything makes it one of the most commonly analyzed isotopes in NMR spectroscopy. | ||
== History of NMR as a technique == | == History of NMR as a technique == | ||
