Final answer:
The catalytic combustion detector is the gas analyzer that requires heating an electrode to 700° C to measure gas concentrations by oxidizing the gas over a heated catalyst.
Step-by-step explanation:
The gas analyzer that requires an electrode to be heated to 700° C is the catalytic combustion detector. This type of detector works by oxidizing the gas sample over a heated catalyst, which causes a change in temperature due to the heat of combustion. The temperature change is then measured and related to the concentration of gas. This process is unlike the operation of the other types of gas analyzers listed, such as the infrared gas analyzer, which measures gas concentrations based on the absorption of infrared radiation, the flame ionization detector that uses a hydrogen flame to ionize organic compounds, or the thermal conductivity detector which works on the principle of thermal conductivity differences between the sample and a reference gas.