The International Mussel Watch 



glass capillary chromatography which often leads to increased dead volume. Low bleed graphite 

 (vespel) ferrules provide a good seal. 



5.4.1.3 Column conditioning: The presence of extraneous peaks and elevated base-line 

 drift will result in poor detector performance. This can be caused by components which elute from 

 the column, such as residual solvents and low molecular weight liquid phase fractions on new 

 columns and a build-up of later eluting compounds on old columns. Conditioning is a necessary 

 step to remove these contaminants. New columns are connected to the inlet while left unconnected 

 to the detector. CAUTION: IF H 2 IS USED AS A CARRIER GAS, POSITION THE COLUMN 

 END OUTSIDE OF THE O VEN),. flushed with carrier gas at low temperature for 15 minutes to 

 remove oxygen from the column, heated at 70-100°C for 30 min. and finally in cyclic temperature 

 programmed runs, with 250°C as end temperature overnight. The column can then be connected 

 to the detector. Old columns can be heated directly at elevated temperatures overnight. The final 

 temperature is selected as a compromise between time required to develop a stable baseline and 

 expected column life. Thus, it may be necessary for older columns to be heated to the maximum 

 temperature of the liquid phase resulting in shorter column life. The temperature of the ECD, when 

 connected to th# column, should always be at least 50°C higher than the column, in order to avoid 

 condensation of material onto the detector foil. It is essential that carrier gas flows through the 

 column at all times when at elevated temperatures. Even short exposure of the column to higher 

 temperature without sufficient flow will ruin the column. 



5.4.1.4 Column test: Column performance tests should be carried out at regular intervals 

 and a continuous record kept in a log book. 



5.4.1.5 Column maintenance: The column remains in optimum condition as long as the 

 liquid phase exists as a thin, uniform film. This requires that the interactive forces between the 

 film and the inside wall of the capillary column dominate over the cohesive interaction within the 

 liquid phase. Conditions which cause the deterioration of the film are: 1. exposure to high 

 temperatures; 2. insufficient gas flow at elevated temperatures; and, 3. sample components which 

 have stronger attractive interaction with the column wall than the liquid phase. The quality of the 

 film at the inlet side may suffer from repeated splitless injections. Decreased column quality may 

 be remedied by the removal of parts of the column (0.1-1.0 m) at the inlet side and/or by heating to 

 the upper limit of liquid phase stability. One should be aware of selective adsorption that can 

 happen with contamination of the column at the injector end. This can be remedied by removal of a 



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