B. Sắc ký khí (Gas-Liquid Chromatography) Thermal Conductivity Detector (TCD) B. Sắc ký khí (Gas-Liquid Chromatography) Flame Ionization Detector (FID) Sensitive towards organics Analyte is burned in H2/air, which produces CH and CHO+ radicals CHO+ radicals are reduced at a cathode which produces a current proportional to the radical quantity 10-12 A Specific for organic carbon, insensitive to inorganics, CO2, SO2 etc. Generally DL 100x less than TCD about pg/s (flow rate dependent) Response to specific organic depends on the number of organic carbons. . | B. Sắc ký khí Gas-Liquid Chromatography Thermal Conductivity Detector TCD Table 24 4 Therma cofbdjctivily at 273 K ốrtd 1 itm Tbariìal vmduú1VĨ y Ct Iff lí 1 t Molecular weight H 2 He 4 NHa 17 Nj 0XC43 28 CHr 00170 Cb Ar 40 C Ht õũõiil M 0 6144 44 Q OJ0076 71 Tic Wft per Uli tfii t tfirt tỂúf bMiitf ÍT1X11 tax m J eddiTfKKii fhff by wk A the ftrrxuJ dKtivKr Uiwti 14 K - L Ad fllir rii c tmpmiljw KftnỈ TlktthftM in nrrỴí ỂÌIM u be di Amun cwfikuM It B u rtui. B. Sắc ký khí Gas-Liquid Chromatography Flame Ionization Detector FID Sensitive towards organics s Analyte is burned in H2 air which produces CH and CHO radicals s CHO radicals are reduced at a cathode which produces a current proportional to the radical quantity - 10-12 A s Specific for organic carbon insensitive to inorganics CO2 SO2 etc. s Generally DL 100x less than TCD about pg s flow rate dependent s Response to specific organic depends on the number of organic carbons. Flame Removable Exit end of column B. Sắc ký khí Gas-Liquid Chromatography Electron Capture Detector ECD Sensitive to electron withdrawing groups especially towards organics containing -F -Cl -Br -I also -CN NO2 J Nickel-63 source emits energetic electrons collides with N2 introduced as makeup gas or can be used as carrier gas producing more electrons Ni-63 e- e- N2 2e- N2 J The result is a constant current that is detected by the electron collector anode . J As an analyte flows through past the Ni-63 source electron capture is possible by electron-withdrawing species A e- A- J Current decreases as a result of e- capture by analyte. This is one of the few instances in which a signal is produced by a decrease in detectable phenomenon. J Very low DL for detected species 10-15g ml for many halogenated .
