Air bubbles during electroporation - (Feb/08/2011 )

Why would air bubbles increase the risk of arcing during electroporation? I think air is less conductive than the liquid and my understanding is that you want lower salt concentrations to reduce the conductivity of the sample, so air shouldn't promote arcing. Why then, does it happen?

I'm not sure but my guess would be (based on my primitive knowledge of physics):

The arcing is equivalent to a lightening bolt or a static shock - you need to have a large potential difference for it to occur, in a normal electroporation, the conductive fluid allows the electric shock to be administered in a controlled fashion with relatively low reisitance. However, when air bubbles are present, they act as a kind of insulator up to a certain point, at which the electricity sparks across the gap (as an arc) in an uncontrolled fashion.