Observations on comprehensive two dimensional gas chromatography coupled with flame photometric detection for sulfur- and phosphorus-containing compounds
A comprehensive two-dimensional gas chromatography (GC [times] GC) system has been coupled to dual channel flame photometric detection (FPD) and evaluated for its performance in the analysis of sulfur- and phosphorus-containing compounds. The detector flow, including hydrogen, air and nitrogen gas was adjusted to achieve the maximum response and peak symmetry during GC [times] GC analysis in the sulfur and phosphorus mode respectively. Peak asymmetry for S-mode ranged from 0.30 to 0.66 and so exhibited considerable tailing for all flame gas settings. The peak asymmetry and peak width at half height (which ranged from 246 to 384 ms) were both relatively sensitive towards detector gas flow settings. By contrast in P-mode, peak asymmetry was almost unaffected by flame gas settings, and peak widths at half height were relatively constant, ranging from 165 to 185 ms. Results showed that increased detector acquisition rate up to 200 Hz distinctly reduced the signal-to-noise ratio, without affecting the modulated peak width. Occurrence of sulfur peak tailing behaviour during GC [times] GC analysis restricted the upper limit of sulfur response linearity range. Detection limits were estimated to be 617 pg/s in S-mode and 45 pg/s in P-mode for GC [times] GC operation, which were higher than the value estimated for 1D GC-FPD operation. The compatibility of GC [times] GC with FPD has been successfully demonstrated for the separation of sulfur-containing organophosphorus (OP) pesticides in S2 and HPO modes, as well as the organosulfur (OS) compounds in diesel and kerosene samples in S2 mode.