Carbon ring electrode

Wong DKY, Ewing AG (1990) Anodic stripping voltammetry at mercury films deposite on ultrasmaU carbon-ring electrodes. Anal Chem 62 2697-2702. 

INTRACELLULAR VOLTAMMETRY WITH ULTRASMALL CARBON RING ELECTRODES... 

Carbon ring electrodes with structurally ultrasmall tip diameters were fabricated as described elsewhere. Electrodes with 3-5 pm tip diameters were used for intracellular voltammetry. Electrodes used for characterization ranged from 3 to 15 im in tip diameter. 

Figure 2. Schematic of a structurally small carbon ring electrode.

Figure 3. Cyclic voltammograms of DA at a carbon ring electrode in pH 7.4 citrate-phosphate buffer. Scan rate 100 mVs. ...

Voltammetry of dopamine at a 4 pm tip diameter carbon ring electrode is shown in Figure 3. A key feature of this electrode is the useful dynamic range for dopamine concentration measurement (micromolar to milli-molar). Additionally, sigmoidal shaped voltammograms are observed at moderate scan rates as expected for ultrasmall electrodes . 

Figure 4. Cyclic voltammograms of 10 M DA, 4-MC and DOPAC at carbon ring electrodes before (solid lines) and after (dashed lines) electrochemical pretreatment. Scan rate 100 mVs i.

Figure 5. Oxidation current observed at 0.76 V vs SSCE at a carbon ring electrode implanted in the DA neuron of Planorbis corneus. Current observed following extracellular DA application (30 ih, 10 M at each arrow) Data obtained from staircase voltammograms (see text). 

Figure 7. Staircase voltammogram (background corrected) obtained at the peak of the response shown in Figure 6 (circles) vs staircase voltammogram obtained in 20 pH DA in vitro (solid line) at the same carbon ring electrode following the intracellular experiment. i = 10 pA, intracellular 5 pA, in vitro.

Carbon ring electrodes can be fabricated with structurally small (1 pm) tip diameter. These electrodes are useful for voltammetric monitoring of catecholamine neurotransmitters in extremely small environments. 

The selectivity for monitoring DA in the presence of its metabolite DOPAC is increased following electrochemical oxidative pretreatment in pH 7.4 citrate-phosphate buffer. Structurally small carbon ring electrodes can be used to monitor the concentration of DA in the cytoplasm of single cells. Transport (uptake) of exogenous DA into the DA neuron of Planorbis corneus has been monitored intracellularly. Intracellular endogenous DA levels following extracellular application of ethanol have also been monitored. These experiments permit estimation of stored DA levels in the cell body of this neuron. 

Intracellular Voltammetry with Ultrasmall Carbon Ring Electrodes... 

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