Conversion of a conventional packed-column gas chromatograph to accommodate megabore columns. I. Evaluation of the system for organophosphorus pesticides.

A conventional packed-column chromatograph was modified for use with a megabore column using a commercial conversion kit, with the intention of developing a multi-residue method for organophosphorus pesticides. The results indicate that the conversion does not affect the resolving power of the megabore column, since fourteen organophosphorus pesticides could be separated in a single injection. The megabore column in such a system proved to be much more efficient than a packed column in terms of resolution and qualitative reproducibility, and comparable with a similar column in a dedicated chromatograph. However, the conversion did not affect the quantitative reproducibility of the system to some degree, as indicated by coefficients of variation between 5 and 27%, although it was determined that the particular nitrogen-phosphorus detector system (filament bead) used in this study was partly responsible for the variation. Nevertheless, calibration curves were obtained down to 0.1 ng per component, and a limit of quantitation of 1.0 ng was established for each component in a sample containing fourteen organophosphorus compounds. The results indicate that the system is sufficiently reproducible to develop a multi-residue method for organophosphorus pesticides in environmental waters.