Onset Characteristics of Aqueous Large Gap Electrosprays

Electrosprays (ESs) have a wide variety of applications. In particular, the onset voltage parameter is of special interest. Our study investigated onset characteristics of aqueous ESs in a negative polarity for capillary tip-plate distances in the range of 0.5-50 cm. Experiments show significant variation of onset voltage with the presence of metal objects in the proximity of the ES. Data analysis shows an increase in onset voltage with the decrease in counterelectrode radius. The region least sensitive to such variation was found for tip-plate distances larger than 20 cm. Onset voltages appear to be in agreement with Smith´s formula for a certain range of the distance studied. Gaps larger than 25 cm have generally shown more significant variations of this formula. The results of the present study can be useful for the design of ESs of larger gaps.