A simple and efficient approach to reversed-phase HPLC method screening.

The development and utility of an efficient HPLC method screening strategy using only four columns for the separation of pharmaceutical compounds and related impurities is presented. The strategy established a two-column approach to enable rapid early method development, along with a four-column approach for commercial method development of the analytical methods utilized to verify the quality of drug substance or drug product. Mobile phases consisted of acetonitrile or methanol with aqueous trifluoroacetic acid for low pH screening, and ammonium hydroxide for high pH screening. Examples are provided to demonstrate the practicality and orthogonality of the method screening process. A unique system suitability check, using commercially available compounds, was incorporated as a tool for troubleshooting and for ensuring adequate system performance prior to screening. Initial testing of the strategy revealed that the columns chosen were successful in leading to assay and impurity methods for 40 pharmaceutical compounds.

Evaluation of methods for measuring amino acid hydrophobicities and interactions.

The concept of hydrophobicity has been addressed by researchers in all aspects of science, particularly in the fields of biology and chemistry. Over the past several decades, the study of the hydrophobicity of biomolecules, particularly amino acids has resulted in the development of a variety of hydrophobicity scales. In this review, we discuss the various methods of measuring amino acid hydrophobicity and provide explanations for the wide range of rankings that exist among these published scales. A discussion of the literature on amino acid interactions is also presented. Only a surprisingly small number of papers exist in this rather important area of research; measuring pairwise amino acid interactions will aid in understanding structural aspects of proteins.