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A comparison of various presentation forms of retention parameters measured in multi-step gradient elution regimes in reversed phase HPLC indicates that retention indices in the scale of n-alkyl phenyl ketones (so-called Smith 0 s RI system) have the maximal reproducibility. However, the determination of these parameters for most hydrophilic compounds eluted before the first reference acetophenone (RI ¼ 800) implies their calculation by extrapolation, that can lead to the high irreproducibility of results, especially in regimes with initial isocratic stages followed by fast gradient elution. This fact explains the necessity of elaboration of a new calculation method based on the extrapolation of retention concentrations, which provides the appropriate interlaboratory coincidence of RI values at least within the range 600-800 i.u. Using this algorithm, retention indices for about 60 phenolic compounds have been determined, that permits us to identify them in complex

by Chromatographic Techniques -[270 refs.]. -(KOCHETOVA, M. V.; SEMENISTAYA, E. N.; LARIONOV, O. G.; REVINA, A. A.; Russ. Chem. Rev. (Engl. Transl.) 76 (2007) 1, 79-90; Frumkin Inst. Phys. Chem. Electrochem., Russ. Acad. Sci., Moscow 119991, Russia; Eng.) -Lindner 23-275

A comparison of various methods for presenting the retention parameters of analyzed compounds in reversed-phase HPLC under the conditions of stepwise gradient elution demonstrated that retention indices (RIs) based on a standard scale of n -alkyl phenyl ketones exhibited the best reproducibility. However, a new procedure for calculating extrapolated RI values under these conditions should be developed for determining the RIs of the most hydrophilic compounds, which are eluted from a column before a reference component (acetophenone). With this procedure, the RIs of more than 40 phenolic and polyphenolic compounds were determined. The addition of spectroscopic characteristics to these RIs was responsible for the reliable identification of the above compounds in complex mixtures of extractive substances of plant origin. Program for calculating linear-logarithmic retention indices [12]REM: PROGRAM for calculation of lin-log retention indices REM: SIMPLEST VERSION REM: you need data about three reference compounds PRINT: "Calculation of lin-log retention indices (from exp. ret. times)"

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