检测器基本原理.ppt

General Overview of Detector Systems Detectors classification Detectors classification Detector Response Characteristics Detector Response Characteristics Detector Response Characteristics Flame Ionization Detector Universal response Ionization detection Mass detector Destructive Flame Ionization Detector Hydrogen is mixed with gas stream at bottom of jet and air or oxygen is supplied axially around the jet Hydrogen flame burns at the tip, which also functions as cathode and it is electrically insulated from the body Collector electrode is above the burner tip Flame Ionization Detector Flame Ionization Detector It responds to all organic compounds except for formic acid Response is greatest with hydrocarbons and decreases with substitution Sensitivity high due to low noise level No response to water, permanent gases, and inorganic compounds simplifies the resolution of components in analysis of aqueous extracts and in air pollution studies Suitable for fast and ultrafast GC applications Flame Ionization Detector Flame Ionization Detector Flame Ionization Detector Electron Capture Detector Selective response Non-destructive Ionization detector principle Concentration-dependent detector Radioactive source 63Ni (10mCi activity) Displaced coaxial-cylinder geometry Electron Capture Detector Electron Capture Detector Electron Capture Detector Electron Capture Detector Electron Capture Detector Radioactive source: Nickel 63 – 370 MBq (10 mCi) Cell volume 450 ?L Operating temperature limit: 400°C Minimum detectable amount: 10 fg of lindane Linear dynamic range: 104 (argon/methane)  103 (nitrogen) Operation mode: constant current pulse-modulated mode Reference current: 0 to 3 nA (0.1 nA steps) Pulse amplitude: 5 to 50 V neg. Pulse width: 0.1 ?s (argon/methane),  0.5 ?s, 1 ?s (nitrogen) Electron Capture Detector Electron Capture Detecto