Amperometry

Amperometry in chemistry is the detection of ions in a solution based on electric current or changes in electric current. Amperometry is used in electrophysiology to study vesicle release events using a carbon fiber electrode. Unlike patch clamp techniques, the electrode used for amperometry is not inserted into or attached to the cell but brought nearby of the cell. The measurements from the electrode originate from an oxidizing reaction of a vesicle cargo released into the medium. Another technique used to measure vesicle release is capacitive measurements. It is the electric current measured between a pair of electrodes. The measured current is directly proportional to the concentration of the analyte. Example: Blood glucose monitor Carbon is used as a working electrode which is coated with mediator and glucose oxidase. Ag/AgCl is used as the reference electrode. The enzyme oxidase catalyzes the reaction of glucose with oxygen. Hydrogen peroxide concentration is measured by oxidation which occurs at +0.6V. H_2O_2 \longrightarrow O_2 + 2H^+ + 2e^- Current is directly proportional to H 2 O 2 concentration this in turn is directly proportional to glucose concentration. If O 2 is low, complete conversion is inhibited. Hence mediator ferrocene is introduced.…

Amperometry in chemistry is the detection of ions in a solution based on electric current or changes in electric current. Amperometry is used in electrophysiology to study vesicle release events using a carbon fiber electrode. Unlike patch clamp techniques, the electrode used for amperometry is not inserted into or attached to the cell but brought nearby of the cell. The measurements from the electrode originate from an oxidizing reaction of a vesicle cargo released into the medium. Another technique used to measure vesicle release is capacitive measurements. It is the electric current measured between a pair of electrodes. The measured current is directly proportional to the concentration of the analyte. Example: Blood glucose monitor Carbon is used as a working electrode which is coated with mediator and glucose oxidase. Ag/AgCl is used as the reference electrode. The enzyme oxidase catalyzes the reaction of glucose with oxygen. Hydrogen peroxide concentration is measured by oxidation which occurs at +0.6V. H_2O_2 \longrightarrow O_2 + 2H^+ + 2e^- Current is directly proportional to H 2 O 2 concentration this in turn is directly proportional to glucose concentration. If O 2 is low, complete conversion is inhibited. Hence mediator ferrocene is introduced. Now, current is directly proportional to the concentration of ferrocene which in turn is directly proportional to glucose concentration. ==Detection methods== ==Principle== In order to record vesicle fusion, a carbon fiber electrode is brought close to the cell. The electrode is held at a positive potential, and when the cargo from a fused vesicle is near the electrode, oxidation of the cargo transfers electrons to the electrode. This causes a spike, the size of which can be used to estimate the number of vesicles, and the frequency gives information about the release probability.

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