title: Double-column gas chromatography using packed pre-columns and glass capillary main columns.
abstract: Methods of column switching are described that make possible back-flushing, heart cutting and trapping. Conventional packed columns are employed as pre-columns for their high sample capacity, and glass capillary columns are used as the main columns for their high separation efficiency. Some typical examples of the application of double-column gas chromatography are presented: (1) solvent cutting for identification and exact quantitative determination of a phosphorus ester impurity in a sample of wheat flour (including trapping); (2) separation of trace amounts of methyl esters of fatty acids by means of back-flushing and trapping; (3) enrichment technique using trapping of trace elements in the front section of the capillary (plus solvent cutting, multiple injection and back-flushing); and (4) coupling a nitrogen-selective detector to the capillary main column to gain additional information. To illustrate the trapping effect, the separation number was determined with and without trapping.
mesh_terms: D002849:Chromatography, Gas / Q000295:instrumentation*; D004952:Esters / Q000032:analysis; D005227:Fatty Acids / Q000032:analysis; D005433:Flour / Q000032:analysis; D005898:Glass; D010755:Organophosphates / Q000032:analysis; D012997:Solvents; D014908:Triticum / Q000032:analysis
chemical_list: D004952:Esters; D005227:Fatty Acids; D010755:Organophosphates; D012997:Solvents; C009549:triethyl phosphate