The use of a differential scanning calorimetry (DSC) with a data reduction system and a commercially available purity program is presented as an alternate method for the determination of the purity of the steroids Norethindrone, Mestranol, and Ethinyl Estradiol currently listed in the United States Pharmacopeia (USP). This method's ability to determine the purity of a material without recourse to the use of a pure reference standard of the same substance has been seen as one of the major advantages of differential scanning calorimetry (DSC).

An evaluation of the applicability of the DSC methodology was carried out using prepared steroid mixtures. Compositions of 1 and 4% of foreign related steroids with each chosen steroid were used to establish predetermined purity levels for subsequent analysis. As the primary objective of this work was to establish an alternate method for the purity evaluation of pharmaceutical grade raw materials, comparison with the current USP and equivalent methodology was carried out. Thus, results also were obtained for both ultraviolet spectrophotometric (USP) and gas chromatographic methods. Good correlation was obtained between the three methods. However, the DSC method proved to have superior characteristics in terms of precision and accuracy and hence offers an attractive and reliable alternative for the determination of the purity of these materials.