Chapter 24 gc
-
Upload
vanessawhitehawk -
Category
Technology
-
view
53 -
download
1
Transcript of Chapter 24 gc
![Page 1: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/1.jpg)
Gas Chromatography
Mobile phase: Gas (H2, He, N2)
Stationary phase: Nonvolatile liquid or solid
Solute: gas or volatile liquid
GC considerations: analyte must be volatile and thermally stable
Factors that influence separationCarrier gas type and velocityColumn temperatureColumn lengthColumn diameterFilm thicknessStationary phase type
![Page 2: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/2.jpg)
Instrument
Apparatus – major components1. Carrier Gas2. Sample Injection System3. Column4. Detector
![Page 3: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/3.jpg)
Gas Chromatography
1. Carrier Gas• Inert• Hydrogen, helium, nitrogen• Often dictated by detector
2. Sample Injection System•Temp. very important•Avoid band broadening•Suitable size (L)•Liquid/Gas: syringes
![Page 4: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/4.jpg)
![Page 5: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/5.jpg)
Gas Chromatography
3. Columns
A. Packed
B. Open Tubular
A. PackedStainless steel or glass
3-8 mm dia1-5 m in length
Fine solid support coated with nonvolatile liqStrong solid support
![Page 6: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/6.jpg)
Gas Chromatography
B. Open Tubular
Fused silica with nonvolatile liquid coated on it
Advantages Higher Rs
Shorter time Less sample
![Page 7: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/7.jpg)
1. wall coated2. support coated3. porous layer
![Page 8: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/8.jpg)
![Page 9: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/9.jpg)
Gas Chromatography
A. Solid Support
Small uniform particles
Good mechanical strength
High surface areaInert at high temperatureUsually 150 – 250 m dia
![Page 10: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/10.jpg)
B. Stationary Phase: Volatile liquid
Low volatilityGood thermal stability
Chemical inertness
“appreciable” solvent power“like dissolves like”
![Page 11: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/11.jpg)
![Page 12: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/12.jpg)
Temperature Programming
Broad range of boiling points
Increase temperature during sepn
![Page 13: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/13.jpg)
![Page 14: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/14.jpg)
Column Diameter
![Page 15: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/15.jpg)
Column Length
![Page 16: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/16.jpg)
Stationary Phase Thickness
![Page 17: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/17.jpg)
![Page 18: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/18.jpg)
Gas Chromatography
4. Detector– Sensitive– Stable – Linear– Versatile– Response time– Selective
Most Common
A. Thermal conductivity
B. Flame Ionization
C. Electron capture
![Page 19: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/19.jpg)
Gas Chromatography
A. Thermal conductivity– Simple– Universal– Change in thermal
conductivity of a gas when an analyte is present
– He, H2 have high TC
Properties
4-5 order of magn linear response
Simple
Responds to all analytes
Low sensitivity relative to others
![Page 20: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/20.jpg)
Temp f(TC)R f(Temp)
Analyte dec TC, inc Temp, inc R
TC detector
![Page 21: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/21.jpg)
Gas Chromatography
B. Flame Ionization
– Burn elutate in a mixture of H2 and air – create ions and electrons
– Response prop. to solute mass
– Insensitive to H2, He, N2, CO2, NH3, carbonyl…
Properties
High sensitivity
Large linear response 107
Destructive
Good detection limits
![Page 22: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/22.jpg)
CH + O CHO+ + 1e-
FI detector
![Page 23: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/23.jpg)
Gas Chromatography
C. Electron Capture– Ionize gas entering detector with high energy electrons– Measure current– Analyte that has affinity for e-, captures them
Properties
Sensitive to halogens, conj. Carbonyls, nitriles, nitro compds
Selective
Small linear range, 102
Non-destructive
![Page 24: Chapter 24 gc](https://reader035.fdocuments.us/reader035/viewer/2022062307/556431d8d8b42ace308b47c6/html5/thumbnails/24.jpg)