How can I determine when to change my guard column?

   Many chromatographers change guard columns after a certain number of samples or standards and samples have been analyzed. This sample number is usually determined experimentally due to earlier column failure from waiting too long to change the guard column or by increasing the number of analyses before guard column change from a more conservative initial value.

   This guard column change interval is usually determined empirically for each method/sample type combination, but many analysts change guard columns either based on a finite number of sample runs or based on some column performance criterion such as a 10% increase in peak width or tailing factor, or a 10% decrease in column efficiency (plates).

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