Gas chromatographic detection of organometallic compounds by reactive-flow photometry

The response of the reactive flow detector (RFD) toward organometallic compounds of several transition metals has been explored, and several of its strong elemental responses have been characterized in detail. The RFDs minimum detectable flow (measured in picograms of metal per second at S/N_p-t-p=2) is 0.1 for ruthenium, 3 for chromium, 10 for manganese, 5 for nickel, 15 for iron, and 2 for osmium. Typically, the linearity of response spans four orders of magnitude, with atomic selectivity of metal versus carbon ranging from 2 to 3 orders. Response quenching by co-eluting hydrocarbons is not observed. As a demonstration experiment, the common analysis of methylcyclopentadienyl manganese tricarbonyl (MMT) in gasoline is carried out on an RFD system modified for dual-channel operation. The results show that dual-channel operation of the RFD can increase the native elemental selectivity of manganese over carbon by a factor of 100, in accordance with earlier results obtained on a special version of the flame photometric detector (FPD). Significant differences exist between the optical spectra of carbon flame species resulting from various combustion modes carried out in the RFD capillary, and also between conventional FPD and typical RFD spectra. Consideration of these spectral differences suggests that the virtual absence of in the reactive flow may be the primary reason why analyte response quenching by hydrocarbons, while prominent in the FPD, is not observed in the RFD.