Question

Which statement is true for flame ionization detectors (FID)?

A)FID employs a beta emitter to ionize the sample.

B)Emission spectra are used to quantify the peak concentration.

C)The FID flame gets cooler in the presence of hydrocarbons eluent.

D)FID relies on the combustion of the sample carbon atoms which produce CH radicals, CHO+ions, and electrons which are then detected.

E)The detector responds by combusting hydrogen gas from the mobile phase.

The term “column bleeding” refers to:_______________.

A)leak of carrier gas from the column.

B)poor resolution of low volatility compounds.

C)stationary phase decomposition.

D)decomposition of analytes on the column.

E)stationary phase contamination.

Answer 1

1. E.) is correct because the detector responds by combusting hydrogen gas from mobile phase,

firstly eluent travels up thedetector, it is mixed with the hydrogen gas and then with the oxidising agent. The mixture of these three continues to travel up to the head of nozzle where a positive voltage exists. This positive voltage is repelled up toward the plates known as collector plates which are connected to an ammeter which is very sensitive, which detects the ions hitting the plates, then it amplifies the signal. The products of the flame finally get out of the detector through the output port. So hydrogen helps in detection.