Extra Column Dispersion - The Use for Low Dispersion Instrumentation with Small Bore Columns to Obtain Ultra High Efficiencies. > Page 64

 

It is seen that the river water and the town water contain significant quantities of soluble organic materials whereas the well water is almost devoid of organic contaminants. The level of the impurities is in the 1 to 100 ppb range. The great attraction of this type of trace analysis is it capacity for almost limitless mass sensitivity and the simple nature of the procedure.

 

The Use for Low Dispersion Instrumentation with Small Bore Columns to Obtain Ultra High Efficiencies.

Small bore columns can be connected in series to lengths of 10 or even 20 meters to provide a proportional increase in overall efficiency. This, at least in theory, can be also achieved using wide (4.6 mm I.D.) columns but, the solvent consumption for such columns would be enormous. The retention volume of a solute eluted at a capacity ratio of 20 on a 10 m column 4.6 mm I.D. would be about 2.8 liters, an unacceptably large solvent consumption An equivalent column 1 mm I.D. would require only 132 ml to elute the same solute. Results from small bore columns up to 14 m in length have been reported.

 

J. Chromatogr.,169(1979)51

Column, length 14 m, I.D. 1 mm, mobile phase tetrahydrofuran, flow-rate 25ml/min, adsorbent Spherisorb 5. Solutes benzene, ethyl benzene, butyl benzene, hexyl benzene,

Figure 33. Chromatogram of a Series of Alkyl Benzenes Separated on a Column having 650,000 Theoretical Plates