INTERLABORATORY APPLICABILITY OF A RETENTION INDEX LIBRARY OF DRUGS FOR SCREENING BY REVERSED-PHASE HPLC IN SYSTEMATIC TOXICOLOGICAL ANALYSIS

The retention indices (RI) of 47 selected acidic, neutral and basic drugs were determined on 7 reversed-phase (octyl- and octadecylsilica) columns in two laboratories in the 1-nitroalkane scale, using either 1-nitroalkane homologues or selected drugs, whose RI values were previously determined on the reference column. Obtained values were compared with the library values, determined previously on the reference column. Retention indices, calculated with drugs as RI markers, showed distinctly lower deviations from the library values and lower inter-column variability: The mean standard deviation of RI for all drugs analyzed on all columns in the 1-nitroalkane scale was 44.3 RI units, against 10.3 units when selected drugs were used as RI markers. The deviations from the listed values, calculated for each column separately with drugs as markers, were in 95% of cases smaller than 20 RI units, and in 80 % smaller than 10 units. The largest differences between the experimental and listed values were observed for column that differed in type of silica support, type of stationary phase (C8 versus C18) or column length in comparison to the reference column. The kind of silica support contributed more to the variability than the type of stationary phase. The results indicate that it is possible to use and exchange HPLC data based on a retention index library.