Several drug substances initially selected for this study failed to progress through the screening process. This was mainly due to a few factors; the first being that there were multiple compounds for which a calibration curve for the analytical HPLC method could not be established. This was caused by a lack of solubility of these compounds in the solvent used for preparation of standards which meant that a standard curve for measurement of solubility of these compounds could not be applied. An often standardized solvent for dissolving poorlysoluble molecules is dimethyl sulfoxide (DMSO); considered a universal solvent because it can dissolve both polar and non-polar molecules . However, since the melting point of pure DMSO is 19°C, it can pose a risk when running high throughput experiments near room temperature, as was the case for the work presented here. As a result, the HTE lab at GSK standardizes on a common "backing solvent" consisting of 62.5% acetonitrile, 25% tetrahydrofuran, and 12.5% HPLC-grade water v/v for all high-throughput experiments on the Unchained Labs CM3 platforms. This backing solvent serves multiple purposes in the HTE lab, and is the primary diluent of choice. The use of this backing solvent has proven beneficial in nearly all applications in GSK's HTE lab, with few exceptions. Using a DMSO-based solution in place of backing solvent would not likely have improved the outcome, since the few compounds that were excluded due to low solubility were not soluble at the lower concentrations of 0.001 mg/mL. One of the goals of this research was to develop a standardized automated approach to measuring the ionization constant and distribution coefficients of a large number of molecules. The utility of the backing solvent selected for this work extends beyond the experiments described here. This solvent mixture is employed in a variety of applications throughout the lab, and is used as the primary diluent for the majority of our experiments, by default. For this reason, we elected not to complicate any aspects of the experimental design by using customized solutions for each individual molecule.