Calibration for Flame Photometry
Why the same sample gives different results
In Flame Photometry a stable flame is vitally important. The open flame of a lighted candle will flicker wildly if someone walks by, but can change even if someone opens a door on the opposite side of the room.
This is why the flame is carefully shielded within the device—to avoid this obvious source of interference. More importantly, the burning gas is under fixed and carefully controlled pressure to maintain flame stability at the burner head.
Even so, environmental factors can alter results. Consider airborne oxides, such as CO2, NO2, or Sulphur Dioxide, whose presence can affect flame temperature and how brightly the flame burns. These pollutants will dull the flame because the oxygen is bound too tightly to react, reducing the locally available oxygen. Indeed even airborne water (humidity) can change your results, as could airborne CH4.