Microcylinder electrodes as sensitive detectors for high-efficiency, high-speed liquid chromatography

A carbon fiber microcylinder electrode (r = 3.5 microns) is used as a detector for high-efficiency and high-speed liquid chromatography. The microcylinder has a detection volume of a few picoliters, and can be placed directly at the outlet frit of the column. With proper positioning equipment, the electrode can be placed at the region of the outlet frit where the separation efficiency is highest. Such selective sampling results in greatly increased measured efficiency over a conventional electrochemical detector when short (4 cm) columns of conventional diameter (3.2 mm) are used. The microcylinder detector is sensitive and subpicomole detection limits are obtained in less than 30 s for norepinephrine. The need for expensive positioning equipment is eliminated by mounting the electrode into a fitting which can be mated directly with the column.