Single nerve cell analysis by capillary electrophoresis with amperometric detection

This paper reports the use of capillary electrophoresis (CE) with electrochemical detection to first detect the amol amount of norepinephrine(NE) and epinephrine(E) in a single sympathetic nerve cell (diameter 15∼25 μm, volume 2∼5 pL) of rat. The home-made CE with electrochemical detection system consists of whole cell sampling, CE and amperometric detection. The whole cell sampling involves a micromanipulator, an inverted microscope and an injection end of the capillary. To aid cell injection, the injection end of the cap, illary was etched to 100 μm with hydrofluoric acid . The CE apparatus consists of 30 kV dc power supply, platinum wires and a fused-silica capillary(25 μm i. d. , 375 μm i. d. , 75 cm length) filled with 25 mmol/L MES buffer solution at pH 6. 5. The amperometric detector used in this experiment was a carbon fiber microelectrode. The carbon fiber having a diameter of 8 μm and a length of 0. 3 mm, was inserted directly into the end of the electrophoresis capillary by micropositioner and microscope. The potential on the carbon fiber working electrode was controlled to 0. 7 V vs. SCE reference electrode by a potentiostat. Currents produced were measured and recorded by a picoammeter and a recorder. Sympathetic ganglia were dissected from rats. After enzymolysis the cells were isolated. The injection end of the capillary was placed adjacent to the cell using micromanipulator under the microscope. The whole cell sampling was accomplished for CE by directly drawing a cell into the tip of a capillary with electroosmotic flow and lysing the cell inside the capillary as observed under the microscope, using a micromanipulator. All separations were performed in 25 mmol MES buffer solution using 18 kV separation potential. The amperometric detector with microelectrode was used for detecting the neurotransmitters. The results in separation and detection the amol amount of NE and E in a single sympathetic nerve cell using this system are satisfactory.