The evaluation of important pharmacokinetic properties such as hydrophobicity using High Throughput Screening (HTS) methods is a major issue in drug discovery. In this article, we present the measurement of the Chromatographic Hydrophobicity Index (CHI) on a subset of the French chemical library, the "Chimiotheque Nationale" (CN). The data was used in QSPR modelling in order to annotate the CN. An algorithm is proposed to detect problematic molecules with large prediction errors, called outliers. In order to find an explanation for these large discrepancies between predicted and experimental values, these compounds were reanalysed experimentally. As the first selected outliers indeed had experimental problems, including hydrolysis or sheer absence of expected structure, we herewith propose the use of QSPR as a support tool for quality control of screening data and encourage the cooperation between experimental and theoretical teams to improve results. The corrected data was used to produce a model, which is freely available on our web server