When carrying out any form of analytical chemistry, it is common for some to achieve one set of results, only to then repeat the process and get a totally different outcome.
Similarly, if two laboratories are studying the same thing, each may run the same test on the same sample but find massive fluctuations in their results.
There are a number of different reasons that can lead to this conclusion.
What factors may influence the intensity of ion emission in flame photometry?
When using a flame photometer, the most obvious point of contention is the stability of the flame.
When you light a candle, you’ll notice how easily someone on the other side of the room can make the flame flicker.
A gas-burning flame photometer mechanistically burns more stable than a solid paraffin wax/wick candle. This is due to the pressure of the gas through the burner head.
What causes low flame stability in flame photometry?
Any tiny changes in the pressure of the surroundings of the flame can cause very low flame stability.
The light emitted from the flame to the photodiodes can cause huge offsets in the output of the diode.
This would also be indicative of general atmospheric pressure, meaning variation of results can occur.
For example, a laboratory at sea level would find a flame burns brighter than one burning on top of a mountain.
This is due to the fact that the oxygen content of the natural air is higher at sea level. This would result in a faster and more complete combustion of the fuel, resulting in more light being emitted from the sample to be collected by the photodiodes.
What might affect the temperature of a flame in flame photometry?
The amount of oxygen present will always affect the temperature of a flame.
However, other factors such as oxides being present in the atmosphere, would also result in a lower combustion ratio.
Oxides such as Carbon dioxide, Nitrogen dioxide and Sulphur dioxide would all, to some degree, effect the burning of the flame and, thus, its stability.
This is due to the way that all reactions work. Even during a combustion reaction, the ratio of products to reactants in the equilibrium affects the rate at which gas burns.
Other factors in your lab which can affect the results of the testing are humidity and pollution levels, especially as these can both fluctuate.
How can I control my results when using flame photometry?
The factors mentioned above can be controlled via the calibration curve and your standards, as the results would then be calibrated for your environment.
This is why it is so vital that you do not let a single calibration curve remain on an instrument over a few days or multiple analyses.
The BWB Flame Photometers also utilise sealed chimneys ensuring that only filtered air is passed to the flame and with the novel built in compressor and gas regulation system the finite control of a flame is vastly more achievable.
Regardless of how clever the instrument is though at controlling the flame conditions, it is still important to calibrate your instrumentation regularly throughout the day, even if you are testing the same sample type. Remember, sample analysis can only be as precise as your last calibration.