lecture17 - GAS CHROMATOGRAPHY GAS Chapter 27 Mobile phase...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
GAS CHROMATOGRAPHY GAS CHROMATOGRAPHY Mobile phase is a gas Mobile phase is a gas Chapter 27 Homework : 1, 2, 3, 7
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Gas Chromatography 1. Introduction 2. Mobile and Stationary phases 3. Gas-Solid and Gas-Liquid Chromatography 4. Detectors
Background image of page 2
Gas Chromatography (GC) Gas Chromatography (GC) GC is currently one of the most popular methods for separating and analyzing compounds. This is due to its high resolution, low limits of detection, speed, accuracy and reproducibility. GC can be applied to the separation of any compound that is either naturally volatile (i.e., readily goes into the gas phase) or can be converted to a volatile derivative. This makes GC useful in the separation of a number of small organic and inorganic compounds. Prerequisite for GC sample: (a) fairly volatile, and (b) thermally stable. A simple GC system consists of: 1. Gas source (with pressure and flow regulators) 2. Injector or sample application system (sample inlet) 3. Chromatographic column (with oven for temperature control) 4. Detector & computer or recorder
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Carrier gas : He (common), N 2 , H 2 Column: 2-100 m coiled stainless steel/glass/Teflon/fused silica, packed vs. unpacked Oven: 0-400 °C ~ average boiling point of sample Detectors: FID, TCD, ECD, NPD, FPD, AED ,PID ,MSD. (SINGLE OR TANDEM) Instrumentation
Background image of page 4
GC separates solutes based on their different interactions between mobile and stationary phases. solute’s retention is determined mostly by its vapor pressure and volatility solute’s retention is controlled by its interaction with the stationary phase Carrier gas – main purpose of the gas in GC is to move the solutes along the column, mobile phase is often referred to as carrier gas (MUST BE INERT!). Common carrier gas : include He, Ar, H 2 , N 2 Carrier Gas or Mobile phase does not affect solute retention, but does affect : 1.) Desired efficiency for the GC System (Van Deemter!) - low molecular weight gases (He, H 2 ) larger diffusion coefficients - low molecular weight gases faster, more efficient separations 2.) Stability of column and solutes - H 2 or O 2 can react with functional groups on solutes and stationary phase or with surfaces of the injector, connections and detector 3.) Response of the detector - thermal conductivity detector requires H 2 or He Mobile Phase Mobile Phase
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Stationary phase in GC is the main factor determining the selectivity and retention of solutes. There are three types of stationary phases used in GC: Solid adsorbents Liquids coated on solid supports Bonded-phase supports 1.) Gas-solid chromatography (GSC) - same material is used as both the stationary phase and support material - common adsorbents include: alumina molecular sieves (crystalline aluminosilicates [zeolites] and clay) silica,active carbon Magnified Pores in activated carbon Mobile Phases Mobile Phases
Background image of page 6
Advantages : - long column lifetimes - ability to retain and separate some compounds not easily resolved by other GC methods geometrical isomers
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/16/2010 for the course CHEM 589 taught by Professor -1 during the Fall '02 term at Pennsylvania State University, University Park.

Page1 / 23

lecture17 - GAS CHROMATOGRAPHY GAS Chapter 27 Mobile phase...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online