Comparability of RP-HPLC Retention Indices of Drugs in Three Databases

Three databases of HPLC retention indices in the 1-nitroalkane scale were recently established (IFM = Institute of Forensic Medicine, MCL = Microchemistry Laboratory, MTSS = Merck Tox Screening System). In two of them (IFM and MTSS) virtually identical chromatographic conditions were applied but different RP-columns. In the third system (MCL) a different column and different elution conditions were used. Among a total of 1149 drugs examined in all three labs, 258 drugs were common for IFM and MTSS, 179 were common for MCL and MTSS, 162 were common for IFM and MCL, and 135 drugs were common for all three databases. Good agreement of retention index values in IFM and MTSS was demonstrated (r2 = 0.9778). The correlations between IFM and MCL and MTSS and MCL data were less strong (r2 = 0.9245 and 0.9339, respectively), due to some deviating results. These deviations concerned mainly substances with pKa values between 1–4 and were probably caused by the differences in the pH of the two mobile phases. ...