Determination of retention indices of polychlorobiphenyls by using other compounds detectable by electron-capture detection or selected polychlorobiphenyls as the reference series

The highest sensitivity to polychlorobiphenyls (PCBs) is offered by electron-capture detection (ECD), but the easy identification of individual congeners remains unresolved. Published retention data are of limited usefulness, as the lack of a uniform style and the dependence on the analysis conditions do not permit their general use. Retention index values of PCBs cannot be easily referred to n-alkanes, due to the very low response of these compounds to ECD, whereas other well detected reference series can be used: n-alkyl iodides were found useful for the determination of retention indices of the first congeners of the PCB series. Retention indices obtained by using selected DCMA (Dry Colour Manufacturers' Association) PCB reference mixtures can be directly used or converted to standard Kovats indices. A mixture of PCBs that shows a linear dependence of retention on the number of chlorine atoms on both isothermal and programmed-temperature analysis is suggested for reference purposes. Other methods and standard mixtures used for identification and quantitation purposes are reviewed and discussed.