For Method 8260, if the instrument is tuned not by direct injection but instead by purging a BFB standard, is it acceptable to use the split ratio to determine the amount of BFB that is actually reaching the mass spectrometer?
Method 8260C specifies a "50 ng or less injection" and gives no room for interpretation. Because the method uses the word "must" and not "may" or "should", use a 50-ng or less injection for BFB tune is required.
Additionally, it is not appropriate to consider the split ratio when injecting, because not all the compounds split evenly (i.e., the split may cause loss of low molecular weight gases (CO2, N2, O2, etc.)/water and solvents such as MeOH). The target compounds are much higher boiling point, and, as such, should be retained at much higher ratios.