ABSTRACT
In the search for new drug candidates, scientists use molecular modeling techniques to identify potentially new structural moieties and screen natural sources or large families of synthetically related compounds, along with modifying exisiting compounds. The United States Pharmacopeia provides extensive discussion on impurities in sections 1086 (Impurities in Offical Articles), 466 (Ordinary Impurities), and 467 (Organic Volative Impurities). A total impurity level of 2.0% has been adopted as a general limit for bulk pharmaceuticals. This chapter contains numerous references to the use of chromatographic methods in the control of plant extracts. Multiple ultraviolet wavelength detection has become a popular approach to evaluating chromatographic peak homogeneity. In the simplest form, the ratio between two preselected wavelengths is measured, and for a homogenous peak, the ratio remains constant. Peak purity can be assessed with a higher degree of certainty only by additional analysis using a significantly different chromatographic mode.
