How is the Linearity of the Pump Measured?

How is the Linearity of the Pump Measured?

The linearity of the pump should be assessed between 0-100% using the conditions described in Figure 1. This is in order to ascertain the ability of the pump to accurately proportionate the mobile phase throughout the gradient, but in particular, at low or high percentages. Proportionating at low or high concentrations puts the most strain on the pumping mechanism.

The method uses a simple mobile phase of water in Line A and uracil dissolved in water as the B mobile phase as the compound has a UV chromophore which can provide a linear response with increasing concentration. The chromatogram produced is a linear response which corresponds to the changing gradient and can highlight any deviation in the pumping mechanism. This can be easily emphasised by adding a line between the top and bottom of the gradient.

Figure 1  Operating conditions for the pump linearity test and a corresponding chromatogram with a line to illustrate linearity throughout the entire gradient.