The most striking difference arose for phosphorus response (as HPO*), which is well known in the FPD and mFPD. Under their respective optimal conditions, it was found that HPO*emission in the worker flames produced S/N values that were about 20 times greater than those observed in the analytical flame over the linear range spanning nearly 6 orders of magnitude. This enhanced response produced an MDL near 2 × 10−13gP/s in the worker flames, which is lower than that reported for the quartz tube mFPD and agrees well with that of a conventional FPD. Fig 6 demonstrates the improvement noted for 1 ng of trimethylphosphite in each mode. As can be seen on the expanded scale shown, the S/N characteristics are much more favorable for this analyte in the optimized worker flame monitoring mode than they are in the optimized analytical flame monitoring mode.