GC034 Flow Control and Measurement

 The measurement and control of carrier gas flow is very important for GC. Column efficiency depends on the linear gas velocity. As a guideline, a typical column of 0.25-mm inner diameter (i.d.) open tubular (OT) column has an optimum of 0.75 mL/min. Nevertheless, the optimum for a given column should be determined experimentally.

For qualitative analysis, it is crucial to have a constant and reproducible column flow rate. If this is accomplished, retention times can be reproduced, and the comparison of retention times is the quickest and easiest technique for compound identification. Two solutes can have the same retention time. However, a solute cannot have 2 different retention times in the same column. Thus, the retention times are characteristics of the solutes, but not unique.

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