Question

Describe the principles of operation for the detectors listed in Question 27-5.

Short answer

a. The principle of operation of thermal conductivity detector is the thermal conductivity of the carrier gas.

b. The principle of operation of atomic emission detector is the passing of the sample through microwave induces plasma.

c. The principle of operation of thermionic detector is the generation of ion current from the combustion of the sample.

d. The principle of operation of the electron capture detector is that the ionized current from the $\beta -$emitter is decreased by the sample and this is detector by the electron capture detector.

e. The principle of operation of flame photometric detector is that the analyte is excited due to low temperature air flame and the emission is detected by the flame photometric detector.

f. The principle of operation of flame ionization detector is the detection of current produced by the sample.

Step-by-step solution

Part (a) Step 1: Given information

States the principles of operation for the thermal conductivity detector.

Part (a) Step 2: Principles of operation for the thermal conductivity detector  

The principle of operation of a thermal conductivity detector is that it senses the changes in the thermal conductivity of the gas and compares it with the hydrogen or helium gas. These gases are known as carrier gas. Thermal conductivity detectors are generally used in gas chromatography.

Part (b) Step 1: Given information

Determine the principle of operation of atomic emission detector.

Part (b) Step 2: Principle of operation of atomic emission detector

The atomic emission detector is closely linked with gas chromatography. The atomic emission detector carry microwave induced plasma in it. When the sample that has to be tested passes through this microwave induced plasma, the molecules inside the sample gets excited and are immediately detected by the atomic emission detector.

Part (c) Step 1: Given information

Determine the principle of operation of thermionic detector

Part (c) Step 2: Principle of operation of thermionic detector

The principle of operation of a thermionic detector is that it has hydrogen flames and the sample that has to be tested goes through combustion in these flames. The sample is then put on a rubidium silicate plate. Here, the ion current is generated which is then picked up by the thermionic detector.

Part (d) Step 1: Given information

Determine the principle of operation of the electron capture detector.

Part (d) Step 2: Principle of operation of the electron capture detector

The principle of operation of the electron capture detector is that it has nitrogen and radioactive $\beta -$emitter. The carrier gas, nitrogen, is ionized by the $\beta -$emitter. The current is produced between the two electrodes due to this. The sample is the introduced to this current and the current decreases. This decrease in current is picked up by the electron capture detector.

Part (e) Step 1: Given information

Determine the principle of operation of flame photometric detector.

Part (e) Step 2: Principle of operation of flame photometric detector

The principle of operation of a flame photometric detector is that it puts the sample that has to be tested in a low temperature air flame. Due to this, the analyte is exited and starts to emit radiation. This radiation is picked up by the flame photometric detector. Flame photometric detector is generally used to detect sulfur and phosphorus.

Part (f) Step 1: Given information

Determine the principle of operation of flame ionization detector.

Part (f) Step 2: Principle of operation of flame ionization detector

The principle of operation of a flame ionization detector is that the sample is ionized by hydrogen flames or air. Current is induced between two electrodes due to this ionization. The magnitude of this induced current is picked up by the flame ionization detector.