Nuclear magnetic resonance wavelength

Spectroscopy produces spectra which arise as a result of interaction of electromagnetic radiation with matter. The type of interaction (electronic or nuclear transition, molecular vibration or electron loss) depends upon the wavelength of the radiation (Tab. 7.1). The most widely applied techniques are infrared (IR), Mossbauer, ultraviolet-visible (UV-Vis), and in recent years, various forms ofX-ray absorption fine structure (XAFS) spectroscopy which probe the local structure of the elements. Less widely used techniques are Raman spectroscopy. X-ray photoelectron spectroscopy (XPS), secondary ion imaging mass spectroscopy (SIMS), Auger electron spectroscopy (AES), electron spin resonance (ESR) and nuclear magnetic resonance (NMR) spectroscopy. 

Copolymer Analysis. Even though the overall copolymer composition can be determined by residual monomer analysis, it still is necessary to have reliable quantitative techniques for copolymer composition measurements on the actual copolymer, mainly because concentration detectors for SEC or HPLC are sensitive to composition and because the conversion histories are not always available. Some of the techniques used to determine copolymer composition are melt viscometry (46), chemical analysis, elemental analysis, infrared spectroscopy (IR), Nuclear Magnetic Resonance (NMR), ultra-violet spectroscopy (UV), etc. Melt viscometry, chemical and elemental analysis are general techniques that can be applied to almost any polymer. The spectroscopic techniques can be applied depending on the ability of the functional groups present to absorb at specific wavelengths. 

An HPLC detector measures the concentration (or mass) of eluting analytes4 by monitoring one of their inherent properties, such as UV absorbance. A detector can be universal to all analytes or specific to particular classes of analytes. Common detectors and their attributes are listed in the Table 4.2. Early HPLC detectors are spectrometers equipped with small flow cells however, most modern units are compact and designed solely for HPLC. The ubiquitous UV/visible variable wavelength absorbance and the photodiode array detectors (PDA) are covered in more depth in this section. Note that mass spectrometers (MS) and nuclear magnetic resonance spectrometers (NMR) are discussed in the section on hyphenated systems. 

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