What device uses ultraviolet light to ionize particles for VOC determination?

• A. Photo Ionization Detector (PID)
• B. Mass Spectrometer
• C. Flame Ionization Detector
• D. Electrochemical Sensor

Answer: (A)

The main idea here is that some detectors identify VOCs by turning the molecules into charged particles using ultraviolet light. A Photo Ionization Detector uses a UV lamp to ionize many volatile organic compounds in the air. When VOCs absorb UV photons with enough energy, they lose an electron and form ions. The detector collects these ions and measures the resulting current, which is proportional to the amount of ionizable VOCs present. This makes the device fast and suitable for real-time monitoring, especially for a broad range of VOCs that have ionization energies below the lamp’s energy.

Other devices don’t use UV ionization. A mass spectrometer ionizes samples (often by electron impact or chemical ionization) and then analyzes the ions by their mass, which is a different principle and equipment level. A flame ionization detector relies on combustion in a flame to produce ions, not UV ionization, and is more about general hydrocarbon detection in a flame. An electrochemical sensor detects gases through redox reactions at a sensor electrode, with no UV ionization involved.