The effective use of gas chromatographic retention data presented in the form of reten¬tion indices (RI) requires the development of a compre¬hensive structure-based digital archive of retention parameters. Development of such an archive includes the collection of all avai¬lab¬le RI values for a variety of compounds including replicates measured under slightly different conditi¬ons. Review of retention data often shows a relatively wide range of RI values for certain well stu¬died compounds that is larger than expected on the basis of the simple reproducibility of experimental measurements. The finding of unusual RI data distributions and their examination pre¬sents a possible way to detect and correct errors during the development of com¬prehensive RI libraries. Our approach involves the construction of histograms representing the distribution of da¬ta points in various RI intervals. The obser¬ved shape of the distribution is compared to the expected and observed shapes for well-identified compounds. Significant sys¬tematic deviations represent anomalies in the sets of RI data. The occurrence of more than a single maximum on a histogram generally indicates the presence of erroneous data. For some compounds such multimode RI distributions may be caused by differences in experimental conditions of the RI determination. The construction and interpretation of histograms for compounds with multiple RI measurements is illus¬trated by several examples. Thus, the RI sub-set for the diterpene alco¬hol, isophytol, was sepa¬rated from the RI data set for phytol and four additional sub-groups of published RI data for one of the sesquiterpenes, gamma-elemene, were re-identified as alpha-, beta-, delta-ele¬menes and germacre¬ne B.
Citation: Journal of Chromatography A
Pub Type: Journals
gas chromatography, gc/ms, retention indices