Chapter22: Gas and Liquid Chromatography12014 - 2015
22.4 Simple Preparation Sample preparation is the process of
transforming a sample into a form that is suitable for analysis.
Solid-phase microextraction is a method to extract compounds from
liquids, air, or even sludge without using any solvent. 2
Syringe barrel
Septum piercing needle Fiber attachment tubingFused silica fiber
with stationary liquid-phase coating Figure 24-24 Syringe for
solid-phase microextraction. The fused silica fiber is withdrawn
inside the steel needle after sample collection and when the
syringe is used to pierce a septum.3
Retract fiber and withdraw needle
Figure 24-25 Sampling by solid-phase microextraction and
desorption of analyte from the coated fiber into a gas
chromatograph. [Adapted from Supelco Chromatography Products
catalog, Bellefonte, PA.]
Expose hot fiber tocarrier gas for fixed time(column is cold)
Piercechromatographyseptum withmetal needleRetract fiberand
withdrawneedleExpose fiberto solution orheadspace forfixed time
withstirringPierce sampleseptum withmetal needle
4
Purge and trap is a method for removing volatile analytes from
liquids or solids (such as groundwater or soil), concentrating the
analytes, and introducing them into a gas chromatograph.5Sample
Cleanup Refers to the removal of undesirable components of an
unknow that interfere with measurement of analyte.
Injection portOvenSample vialPurge gasAdsorption tubeSilanized
glass woolStrongestadsorbentStrongeradsorbentModerateadsorbent
Figure 24-27 Purge and trap apparatus for extracting volatile
substances from a liquid or solid by flowing gas.AB6
Chapter26: Chromatographic Methods and Capillary
Electrophoresis7
26-1. Ion-Exchange Chromatography In ion-exchange
chromatography, retention is based on the attraction between solute
ions and charged sites bound to the stationary phase. In anion
exchangers, positively charged groups on the stationary phase
attract solute anions. Cation exchangers contain covalently bound,
negatively charged sites that attract solute cations.8
