NMR (nuclear method resonance) spectroscopy is the method of choice for the investigation of complex fluid mixtures with analytically similar compounds, where other analytical methods (e.g., optical spectroscopy such as UV/ VIS , infrared (IR), Raman, or fluorescence spectroscopy) suffer from insufficient differentiation of components. In addition, the high value of NMR in determining chemical structure and accurate quantitation, more subtle features such as speciation (e.g., protonation) are clearly indicated. Many samples are sensitive to changes in concentration Ph, temperature, or pressure so that chromatographic methods may be ruled out. A major advantage of NMR spectroscopy is that no calibration is needed for quantification in most cases, and …show more content…
The DSC analysis is depicted in a graph of heat flux as a dependent of time or temperature. The DSC instrument will interpret exothermic reactions by producing positive or negative peaks, depending on the manufacturing technology.
DSC is a popular technique for phase diagram studies of samples. The most common theoretical DSC curves are those observed for fusion, crystallization and glass transition temperatures. For instance, at increased temperature, amorphous semicrystalline solid molecules will become less viscous and have enough freedom of motion to rearrange the molecular structure spontaneously into crystalline form. The
Value of crystallisation temperature, Tc, indicates this as an exothermic process.
Conversely, as the temperature increases to melting temperature, Tm, the sample will have enough energy to melt, indicated as an endothermic curve. Similarly, glass transition temperature, Tg, will be reached as the temperature of an amorphous solid increases. On the DSC curve, Tg appears as a step in the baseline of the recorded DSC