CHEM 212 Lecture 32: Nov 25, 2016
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Department
Chemistry
Course Code
CHEM 212
Professor
Hamilton M.Coreen

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Chem 212!
Nov. 25/ 2016!
!
GC Detectors
-many types e.g. TCD, FID, ECD and MS!
-can combine GGC with Mass spec --> GC/MS or GC/MS/MS or LS/MS/MS!
"-separation technique plus characterization technique!
"-powerful quantitative and qualitative tools!
-ideally signal is proportional to amount go compound!
!
Thermal Conductivity, TCD!
-senses change sin conductivity of stationary phase when a compound is eluting!
-universal detector:r expounds to everything!
-Large linear range --> *********!
-Non-destructive---> doesn't break up your molecule like a mass spec!
-Not very sensitive: 10^-8 g solute/mL!
-Used for gas analysis and prep scale!
"-collecting a fraction!
!
Flame ionization, FID!
-Small H2/O2 flame pyrolyzes sample compounds creating ionic species!
-Ionic species are sensed via a current between 2 electrodes!
-Signal proportional to number of carbon atoms!
-Used for hydrocarbons!
-Large linear range !
-General purpose organics detector!
Destroys sample!
-Moderately sensitive 10^-13 g/mL!
!
Electron capture, ECD!
-Use of 63Ni source to cause movie phase to emit electrons!
-If sample components can capture these electrons, see a decrease in current = signal!
-Very selective response i.e. electronegative functional groups such as halogens, nitro and
phosphate groups!
-Non-destructive!
-Very sensitive 10^-15 g/mL!
-tends to be used for compounds with halogens or nitrogen containing compounds !
-came into the world in the 80s when the world realized how bad PCBs are!
!
Mass Sepctroscopy, GC/MSD!
-Each component eluted from the GC is sent to a mass spectrometer!
-Obtain MS spectrum of each compound separately!
-Powerful identification tool and also good for quantification!
-High resolution MS extremely sensitive 10^-18 g/mL!
"-very little noise because looks at very small area!
-cost about half a million dollars!
!
Application of GC - Both Qualitative and Quantitative
Qualitative!
-By retention time-!

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Description
Chem 212 Nov. 25 2016 GC Detectors many types e.g. TCD, FID, ECD and MS can combine GGC with Mass spec > GCMS or GCMSMS or LSMSMS separation technique plus characterization technique powerful quantitative and qualitative tools ideally signal is proportional to amount go compound Thermal Conductivity, TCD senses change sin conductivity of stationary phase when a compound is eluting universal detector:r expounds to everything Large linear range > ********* Nondestructive> doesnt break up your molecule like a mass spec Not very sensitive: 10^8 g solutemL Used for gas analysis and prep scale collecting a fraction Flame ionization, FID Small H2O2 ame pyrolyzes sample compounds creating ionic species Ionic species are sensed via a current between 2 electrodes Signal proportional to number of carbon atoms Used for hydrocarbons Large linear range General purpose organics detector Destro
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