1 Gas Chromatography (GC; GLC; GSC) “Basic Gas Chromatography” by McNair, Wiley, 1997 “Modern Practise in GC” by Grob, pp. 900 “Gas Chromatography” by Willett, pp. 250 (Wiley) Martin and Synge – 1941 idea; 1952 instrument – 1969 Nobel prize Manufacturers – Perkin Elmer, Hewlett Packard, Shimadsu, Phillips, Carlo Erba, Varian, etc – price? inexpensive; many per laboratory Separation technique — pure n’ simple – partitioning between two phases
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1 Gas Chromatography (GC; GLC; GSC) “Basic Gas Chromatography” by McNair, Wiley, 1997 “Modern Practise in GC” by Grob, pp. 900 “Gas Chromatography” by.
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1Gas Chromatography (GC; GLC; GSC)“Basic Gas Chromatography” by McNair, Wiley, 1997“Modern Practise in GC” by Grob, pp. 900“Gas Chromatography” by Willett, pp. 250 (Wiley) Martin and Synge
– 1941 idea; 1952 instrument– 1969 Nobel prize
Manufacturers – Perkin Elmer, Hewlett Packard, Shimadsu, Phillips, Carlo
Erba, Varian, etc– price? inexpensive; many per laboratory
Separation technique — pure n’ simple– partitioning between two phases
2Schematic GC apparatus Liquid sample of
ca. 0.1l volume injected via a syringe into heated injector port where it is rapidly volatilised and swept by a stream of flowing (carrier) gas thru a column & out via a detector.
D SI GNALI NJECT OR PORT
COLUMNOVEN
CARRI ERGAS
3Impurities in styrene 60m Innowax, 2ml/min He, 1l split 80:1, 80C (9min), 5C/min to 150C
4Schematic gas chromatograph Carrier gas (high purity, unreactive, cheap): N2, He, H2
Flow control» constant, reproducible flow rate
Injection port (sample inlet, microlitre syringe) Oven — thermostatted at constant T or linear rate Column Detector Data processing
10Flame ionization detector MDQ — 5 picograms / second Response — quasi-universal Linearity — excellent (over 106) Stability — flow and temperature insensitive Temperature limit — 400 C Carrier gas — Nitrogen, helium or hydrogen Summary
– Rugged– non-responsive to water and air (“inorganics”)– destructive and – very widely used
11Flame photometric detector MDQ — 1 nanogram S (394 nm); 0.1 ng P (526 nm) Response — effectively only S and P compounds Linearity — moderate (104) Stability — good Temperature limit — 400 C Carrier — nitrogen Summary
– very selective– flame needs clean hydrogen/air supply– expensive but invaluable for pesticide and air pollution work
12Flame photometric detector Sulphur mode; 394 nm
– large solvent peak– small hydrocarbon peak
(pentadecane) for 4,000 ng– dodecanethiol (IS) 20 ng– methyl parathion 20 ng
-particles (fast electrons) which are converted into slow electrons by collision with N2 carrier gas
These are captured by molecules to form a slower moving anions
Reduction in current as compound flows through detector
amplifi er signal
63Ni or 3H
+
carr ier gas
16ECD: organohalogen pesticides
Column DB-210+ 15 m x 0.53 mm id; film 1.0 m He carrier; 100-220C at 3C/min. 600pg each
– 2-lindane; 4-aldrin; 9-dieldrin; 13-DDT
17Electron capture detector MDQ — very high sensitivity (picogram range) Response — very selective (halogenated compounds only)
Linearity — Poor ( 500 to 104) Stability — fair Temperature limit — 220 C (3H) or 350 C (Ni) Carrier — nitrogen or argon + 10% methane Summary
– easily contaminated, carrier must be dry– non-destructive– requires license for radioactive source
18ECD; biphenyls at 30 ppb eachMDQ: 10 fg lindane in 2l injection
19The column Two kinds
– capillary (WCOT: 0.2 to 5 m film thickness, PLOT) » 0.3mm id 50m 300,000 plates 0.01ml 2 ml/min
– packed » 3mm id 2m 3,000 plates 10ml 40 ml/min
Liquid phase– low vapour pressure over operating range & thermally stable – chemically inert to solutes– good solvent for solutes used and low viscosity