Is Make-up Gas required for an FID if not being monitored?

Hello,

Most detectors use a makeup gas to increase the flow rate through the detector body. This quickly flushes peaks out of the detector, avoiding component mixing and loss of resolution. it also optimizes the detector response and eliminate peak broadening (inside the FiD). Peak broadening will occur if there are dead volumes or large detector volumes in the system. This is especially important for capillary columns because the column flow rates are so small.

The signal from mass flow responsive detectors, such as the FID, is not significantly affected by the makeup gas, while the sensitivity and signal to noise ratio are positively influenced by the makeup gas.

Another advantage of makeup: it leads the combustion products (CO2/H2O), especially water, cleanly out of the FiD: it reduces the risk of corrosion!

regards, M

Hello,

Most detectors use a makeup gas to increase the flow rate through the detector body. This quickly flushes peaks out of the detector, avoiding component mixing and loss of resolution. it also optimizes the detector response and eliminate peak broadening (inside the FiD). Peak broadening will occur if there are dead volumes or large detector volumes in the system. This is especially important for capillary columns because the column flow rates are so small.

The signal from mass flow responsive detectors, such as the FID, is not significantly affected by the makeup gas, while the sensitivity and signal to noise ratio are positively influenced by the makeup gas.

Another advantage of makeup: it leads the combustion products (CO2/H2O), especially water, cleanly out of the FiD: it reduces the risk of corrosion!

regards, M

So the make-up also acts as a kind of cleaning agent, removing things you don't want building up in the system? Interesting.

We don't use the FID signal as part of our results for these instruments, so peak broadening etc, really doesn't matter to us that much, I just want to ensure that I wouldn't damage the detector by not running a make-up through it

As a fall back, and if we did need to use the signal to check cut points etc, could we put through a number of runs on a method which does run Make-up gas, clean out the FID and then use it? 

The probability of water precipitation is very low if the FID temperatures are high enough, but in times of 5890 the FID could not ignite well when water was present.

In principle a FID can be operated without makeup gas, which manufacturers officially cannot approve ;-)
In order to fill the detector volume better, an increase of the burner gas could be useful (45/450ml)

You are welcome,
to benefit from your success, it would be great if you would share your results here ;-)

Thanks very much!