An atmospheric pressure ion lens to improve electrospray ionization at low solution flow‐rates

The performance of a reduced flow‐rate electrospray ion source is substantially improved by the addition of an atmospheric pressure ion lens near the tip of the tapered sprayer. The magnitude and stability of ion signals, detected within a mass spectrometer, are significantly improved. In addition, the ion lens decreased the dependence of the ion signals on the sprayer position. These benefits are believed to be due to an improvement in the shape of the equipotential lines near the tip of the electrospray ion source.