THERMALLY-INDUCED FLUCTUATIONS OF THE ELECTRIC-CURRENT AND BASE-LINE IN CAPILLARY ELECTROPHORESIS

Fluctuations of the electric current and baseline that appear in air-cooled capillaries when a high voltage is applied were studied both theoretically and experimentally. The theoretical part relates the amplitudes of the baseline and electric current fluctuations with the fluctuations of the buffer temperature originating from the thermal fluctuations at the outer surface of the capillary. It is shown theoretically that an increase in the outer diameter of the capillary decreases the amplitudes of the electric current and the baseline fluctuations and does not lead to a substantial elevation of the buffer temperature. Experiments confirmed the mutual correlation of the baseline and current fluctuations as predicted by the theory. Jacketing of the outer surface of the capillary with a polymer tubing is shown to be useful for reducing the fluctuations in capillary electrophoresis units lacking liquid cooling.