Differential scanning calorimetry purity determination

CRYOSCOPIC AND DIFFERENTIAL SCANNING CALORIMETRY PURITY DETERMINATION... 

Plato, C. and Glasgow, A.R., Jr. Differential scanning calorimetry as a general method for determining the purity and heat of fusion of high-purity organic chemicals. Application to 95 compounds, Anal. Chem., 41(2) 330-336, 1969. 

NIRA provides a non-destructive alternative to differential scanning calorimetry for the determination of polymorphic forms of drugs, e.g. the polymorphic forms of caffeine. NIRA has also been used to determine optical purity. While the pure opposite enantiomers of a substance have identical NIR spectra, mixing two... 

Donnelly, J.R., L.A. Drewes, R.L. Johnson, W.D. Munslow, K.K. Knapp, and G.W. Sovocool, 1990. Purity and heat of fusion data for environmental standards as determined by differential scanning calorimetry. Thermochim. Acta 167 155-187. 

In most cases, the purity of a pharmaceutical substance is determined by comparison of the reference standard with the known purity assigned. On the other hand, when no reference standard sample is available, the purity is determined by an absolute method in which the calculated result is based on theory and not by a comparative method. Purity established by analytical methods such as phase-solubility analysis or differential scanning calorimetry (DSC) is known as absolute purity (Figs. 3 and 4). 

The determination of the enantiomeric purity of many organosilanes has been achieved by the method of differential scanning calorimetry devised by Jacques, Fouquey, and colleagues (93, 94) this method is of wide applicability and high precision. 

Differential scanning calorimetry directly measures the heat flow to a sample as a function of temperature. A sample of the material weighing 5 to 10 g is placed on a sample pan and heated in a time- and temperature-controlled manner. The temperature usually is increased linearly at a predetermined rate. DSC is used to determine specific heats (Fig. 10-11), glass transition temperatures (Fig. 10-12), melting points (Fig. 10-13) and melting profiles, percent crystallinity, degree of cure, purity, thermal properties of heat-seal packaging and hot-melt adhesives, effectiveness of plasticizers, effects of additives and fillers (Fig. 10-14), and thermal history. 

Palermo E, Chiu J (1976) Critical Re view of Methods for the Determination of Purity by Differential Scanning Calorimetry. Thermochim Acta 14 1-12. 

Plato C, Glasgow AR, Jr (1969) Differential Scanning Calorimetry as a General Method for Determining the Purity and Heat of Fusion of High-purity Organic Chemicals. Application to 95 compounds. Anal Chem 41 330-336 (1969). 

High-purity materials are available as pure solids for chemical uses such as metals used as reference substances for metallurgical analysis, and compounds used as primary standards for many types of titrimetry, and as standards for elemental microanalysis. Other available high-purity substances intended for diverse physical properties include ion activity standards for the calibration of pH and ion-selective electrodes standards for various thermodynamic uses including melting point determinations, differential scanning calorimetry and bomb calorimetry and standards for the calibration of spectrophotometers. 

---