Which detector uses a 10.6 eV bulb and can only detect substances with ionization potential <= 10.6 eV?

• A. MX908
• B. QRAE
• C. PID
• D. MiniRAE 3000

Answer: (C)

Photoionization detectors rely on ultraviolet light to ionize volatile organic compounds. A lamp that emits photons with 10.6 eV of energy can ionize molecules whose ionization potential is at or below that energy. When a molecule is ionized, the resulting charged particles create a current that the instrument measures, giving a signal proportional to the VOC concentration. Molecules with higher ionization potentials won’t be ionized by this lamp, so they won’t be detected by this method. That specific capability—the use of a 10.6 eV lamp to detect substances only if their ionization potential is 10.6 eV or lower—defines a photoionization detector.