These values are identical to those used previously in the mFPD [38] with the exception of the 12 mL/min analytical flame oxygen flow, which is larger than the typical 7mL/minused earlier in the quartz tube prototype [38–40], and was found to provide improved S/N ratios here for sulfur test analytes. Conversely, such a flow increase was not possible with the previous quartz tube design since it resulted in a large background emission at the counter-current flame and worse response. Thus, this new channel may also provide greater flexibility for optimization