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I saw on the talk page that you mentioned you want to add to the principles section. I think it would be really cool if you provide an analogy to help the reader understand the concept (if possible). I understand that it is complex, but I have been looking for 10 minutes and still don't really know what's going on. Maybe you could even draw a really simple figure that would illustrate the analogy. Just an idea. --Theyellowdart22 (talk) 22:20, 11 November 2015 (UTC)
I really like your figure that you made! Nice job! Way to explain things simply. --Theyellowdart22 (talk) 21:22, 7 December 2015 (UTC)
Fast-scan cyclic voltammetry
Principles
In fast-scan cyclic voltammetry (FSCV), a small carbon fiber electrode (micrometer scale) is inserted into living cells, tissue, or extracellular space.[1] The electrode is then used to quickly raise and lower the voltage in a triangular wave fashion. When the voltage is in the correct range (typically ±1 Volt) the compound of interest will be repeatedly oxidized and reduced.[2] This will result in a movement of electrons in solution that will ultimately create a small alternating current (nano amps scale).[3] By subtracting the background current created by the probe from the resulting current, it is possible to generate a voltage vs. current plot that is unique to each compound.[1] Since the time scale of the voltage oscillations is known, this can then be used to calculate a plot of the current in solution as a function of time. The relative concentrations of the compound may be calculated as long as the number of electrons transferred in each oxidation and reduction reaction is known.[1]
Advantages such as chemical specificity, high resolution, and noninvasive probes make FSCV a powerful technique for detecting changing chemical concentrations in vivo.[3] The chemical specificity of FSCV is derived from reduction potentials. Every compound has a unique reduction potential, and so the alternating voltage can be set to select for a particular compound.[1] As a result, FSCV can be used to measure a variety of electrically active biological compounds such as catacholamines, indolamines, and neurotransmitters.[3] Concentration changes regarding ascorbic acid, oxygen, nitric oxide, and hydrogen ions (pH) can also be detected.[4] It can even be used to measure multiple compounds at the same time, as long as one has a positive and the other has a negative redox potential.[4] High resolution is achieved by changing the voltage at very high speeds, referred to as a fast scan rate. Scan rates for FSCV are on the sub-second scale, oxidizing and reducing compounds in microseconds. Another advantage of FSCV is its ability to be used in vivo. Typical electrodes consist of small carbon fiber needles that are micrometers in diameter and able to be noninvasively inserted into live tissues.[4] The size of the electrode also permits it to probe very specific brain regions. Thus, FSCV has proved to be effective in measuring chemical fluctuations of living organisms and has been used in conjunction with several behavioral studies.
Acceptable voltage and current ranges are common limitations of FSCV. To start, the electric potential must stay within the voltage range of the electrolysis of water (Eo = ± 1.23).[5] Additionally, the resulting current must remain low in order to avoid cell lysis as well as cell depolarization.[2] Fast scan cyclic voltammetry is also limited in that it only makes differential measurements; the currents it measures are only relative to the background, so they cannot be used to quantify resting concentrations.[3] This is partially due to the fact that the basal current levels are largely effected by factors such as pH, so over longer periods of time these values tend to drift. The age of the electrode is also important, and probes tend to be less accurate the longer they are used. In order to expand the temporal resolution of this technique, future improvements will need to be made to the microelectrodes. However, for the time being FSCV remains effective in measuring short term changes in concentration.
This technique is also limited to quantifying the concentrations of electrically active compounds, and can only be used with select molecules in biological systems. In spite of this, there have been methods developed to measure levels of non-electric enzymes that have an electroactive substrate.[2] However in this scenario, the electrode probes are also a limiting factor in the data resolution. When measuring an electroactive substrate, the probe is often coated with its corresponding enzyme. In order to avoid the enzyme interacting with different substrates, the electrode is also coated with a polymer that acts as a selective filter against particular types of ions.[2] However, when this polymer is added it lowers the speed at which the voltage scans can be made and effectively lowers the data resolution.
Do you want to add anything about when it was first developed? It might be interesting... Theyellowdart22 (talk) 21:24, 7 December 2015 (UTC)
Images to include:
References: mostly focusing on applications of voltammetry
[1] {good older article explaining the method}
References
edit- ^ a b c d e David O. Wipf, Eric W. Kristensen, Mark R. Deakin, and R. Mark Wightman. Fast-scan cyclic voltammetry as a method to measure rapid heterogeneous electron-transfer kinetics. Analytical Chemistry 1988 60 (4), 306-310 DOI: 10.1021/ac00155a006
- ^ a b c d e Wassum KM, Phillips PE. Probing the neurochemical correlates of motivation and decision making. ACS Chem Neurosci. 2015 Jan 21;6(1):11-3. doi: 10.1021/cn500322y. Epub 2014 Dec 19. Review. PMID 25526380; PMC 4304500
- ^ a b c d e Robinson DL, Venton BJ, Heien ML, Wightman RM. Detecting subsecond dopamine release with fast-scan cyclic voltammetry in vivo. Clin Chem. 2003 Oct;49(10):1763-73. Review. PMID 14500617.
- ^ a b c d R. Mark Wightman. Probing Cellular Chemistry in Biological Systems with Microelectrodes. Science 17 March 2006: 311 (5767), 1570-1574. [DOI:10.1126/science.1120027]
- ^ a b Peter Atkins (1997). Physical Chemistry, 6th edition (W.H. Freeman and Company, New York).
- ^ Ferris MJ, Calipari ES, Yorgason JT, Jones SR. Examining the complex regulation and drug-induced plasticity of dopamine release and uptake using voltammetry in brain slices. ACS Chem Neurosci. 2013 May 15;4(5):693-703. doi: 10.1021/cn400026v. Epub 2013 May 6. Review. PMID 23581570; PMC 3656744.
- ^ Liu T, Han L, Du C, Yu Z. Redox potentials of dopamine and its supramolecular complex with aspartic acid. Russian Journal of Physical Chemistry A. 2014 July; 88(7):1085-1090.