HOW ARE IONS FORMED FROM ELECTROSPRAYED CHARGED LIQUID DROPLETS

The dependence of ion intensities on capillary position has been investigated for electrosprayed solutions of 5 x 10(-6) M (CH3)4 NBr and 10(-3) M CH3COOH in CH3OH + H2O + CCl4. It was found that the efficiencies for desorption from the charged liquid droplets into the gas phase are in the order (CH3)4+ > NH4+ > CH3OH2+. The intensities of ions with higher desorption efficiencies become strong near the periphery of the spray cone, whereas those with lower desorption efficiencies have maxima in the central region of the spray cone. With increase of the vertical distance between the capillary tip and the sampling orifice, the distribution of the space-charge density becomes nearly uniform in the spray cone due to the space-charge field.