Diameter, column, resolution enhancement

The optimum flow rate for most SEC separations using conventional PLgel column dimensions (internal diameter 7.5 mm) is 1.0 ml/min. It may be of some benefit to work with lower flow rates, particularly for the analysis of higher molecular weight polymers where the reduced flow rate improves resolution through enhanced mass transfer and further reduces the risk of shear... 

Santa Clara, CA). The column had a diameter of 3.2 mm, and the exit frit was crimped into place so that a column end fitting was not required. The geometry of the electrochemical cell is shown in Figure 4. The chromatographic system included a pneumatically operated loop Injector (Model 3XL, Scientific Systems, Inc., State College, PA). The injection loop had a 10 pL volume, and mixtures of catecholamines were used as test compounds. The electrode could be positioned with 100 pm resolution in three dimensions with a micromanipulator (Narlshige Co., Ltd., Tokyo, Japan). The vertical resolution was enhanced with a piezoelectric positioner with 0.5-pm resolution (Burleigh Instruments, Inc., Fishers, NY). 

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