Volume 35, Issue 4 (July 1990)
Interlaboratory Reproducibility of Retention Indices in Capillary Gas Chromatography
Because of the temperature-dependent behavior of Kovat's retention indices (RI), based on straight-chain alkane homologues and a liquid phase such as SE-30. OV-1. or methyl silicone, the interlaboratory reproducibility of these RIs determined on capillary columns is comparable to those determined on packed columns. Other homologue series investigated—including diisopropyl-n-alkylamines (DIPA), tri-n-alkylamines (TAA), and 1-nitro-n-alkanes (NIA)—showed the same phenomenon. However, by using a carefully selected reference drug mixture, a dramatic gain in the interlaboratory reproducibility of RI values can be obtained, even under vastly different operational conditions. This allows a search window of ±25 RI units for capillary methyl silicone columns, which is much better than the ±60 RI units that must be applied when using alkane or substituted alkane homologues.