Anodic stripping voltammetry
Anodic stripping voltammetry is a voltammetric method for quantitative determination of specific ionic species. The analyte of interest is electroplated on the working electrode during a deposition step, and oxidized from the electrode during the stripping step. The current is measured during the stripping step. The oxidation of species is registered as a peak in the current signal at the potential at which the species begins to be oxidized. The stripping step can be either linear, staircase, squarewave, or pulse.
Electrochemical Cell Set-Up
Anodic stripping voltammetry usually incorporates three electrodes, a working electrode, auxiliary electrode (sometimes called the counter electrode), and reference electrode. The solution being analyzed usually has an electrolyte added to it. For most standard tests, the working electrode is a bismuth or mercury film electrode (in a disk or planar strip configuration). The mercury film forms an amalgam with the analyte of interest, which upon oxidation results in a sharp peak, improving resolution between analytes. The mercury film is formed over a glassy carbon electrode. A mercury drop electrode has also been used for much the same reasons. In cases where the analyte of interest has an oxidizing potential above that of mercury, or where a mercury electrode would be otherwise unsuitable, a solid, inert metal such as silver, gold, or platinum may also be used.
Anodic stripping voltammetry usually incorporates 4 steps if the working electrode is a mercury film or mercury drop electrode and the solution incorporates stirring. The solution is stirred during the first two steps at a repeatable rate. The first step is a cleaning step; in the cleaning step, the potential is held at a more oxidizing potential than the analyte of interest for a period of time in order to fully remove it from the electrode. In the second step, the potential is held at a lower potential, low enough to reduce the analyte and deposit it on the electrode. After the second step, the stirring is stopped, and the electrode is kept at the lower potential. The purpose of this third step is to allow the deposited material to distribute more evenly in the mercury. If a solid inert electrode is used, this step is unnecessary. The last step involves raising the working electrode to a higher potential (anodic), and stripping (oxidizing) the analyte. As the analyte is oxidized, it gives off electrons which are measured as a current.
Stripping analysis is an analytical technique that involves (i) preconcentration of a metal phase onto a solid electrode surface or into Hg (liquid) at negative potentials and (ii) selective oxidation of each metal phase species during an anodic potential sweep.
Stripping analysis has the following properties:
- Very sensitive and reproducible (RSD<5%) method for trace metal ion analysis in aqueous media.
- Concentration limits of detection for many metals are in the low ppb to high pptrange (S/N=3) and this compares favorably with AAS or ICP analysis.
- Field deployable instrumentation that is inexpensive.
- Approximately 12-15 metal ions can be analyzed for by this method.
- The stripping peak currents and peak widths are a function of the size, coverage and distribution of the metal phase on the electrode surface (Hg or alternate)
Anodic stripping voltammetry can detect μg/L concentrations of analyte. This method has an excellent detection limit (typically 10−9 - 10−10 M)
Stripping voltammetry (Anodic, Cathodic and Adsorptive) have been employed for analysis of organic molecules as well as metal ions. Carbon paste, glassy carbon paste, glassy carbon etc. electrodes when modified are termed as chemically modified electrodes. Chemically modified electrodes have been employed for the analysis of organic molecules (viz., Paracetamol, aspirin, caffeine, phenol, catechol, resorcinol, hydroquinone, dopamine, L-dopa, epinephrine, nor epinephrine, methyl parathion, ethyl parathion, venlafaxine, desvenlafaxine, imipramine, trimipramine, desipramine etc.) as well as metal ions (bismuth, antimony etc.).
- Cathodic stripping voltammetry
- Adsorptive stripping voltammetry
- Electroanalytical Methods
- Sanghavi, Bankim; Srivastava, Ashwini (2010). "Simultaneous voltammetric determination of acetaminophen, aspirin and caffeine using an in situ surfactant-modified multiwalled carbon nanotube paste electrode". Electrochimica Acta 55: 8638–8648. doi:10.1016/j.electacta.2010.07.093.
- Sanghavi, Bankim; Mobin, Shaikh; Mathur, Pradeep; Lahiri, Goutam; Srivastava, Ashwini (2013). "Biomimetic sensor for certain catecholamines employing copper(II) complex and silver nanoparticle modified glassy carbon paste electrode". Biosensors and Bioelectronics 39: 124–132. doi:10.1016/j.bios.2012.07.008.
- Sanghavi, Bankim; Srivastava, Ashwini (2011). "Simultaneous voltammetric determination of acetaminophen and tramadol using Dowex50wx2 and gold nanoparticles modified glassy carbon paste electrode" 706. pp. 246–254. doi:10.1016/j.aca.2011.08.040.
- Sanghavi, Bankim; Srivastava, Ashwini (2011). "Adsorptive stripping differential pulse voltammetric determination of venlafaxine and desvenlafaxine employing Nafion–carbon nanotube composite glassy carbon electrode". Electrochimica Acta 56: 4188–4196. doi:10.1016/j.electacta.2011.01.097.
- Sanghavi, Bankim; Hirsch, Gary; Karna, Shashi; Srivastava, Ashwini (2012). "Potentiometric stripping analysis of methyl and ethyl parathion employing carbon nanoparticles and halloysite nanoclay modified carbon paste electrode". Analytica Chimica Acta 735: 37–45. doi:10.1016/j.aca.2012.05.029.
- Mobin, Shaikh; Sanghavi, Bankim; Srivastava, Ashwini; Mathur, Pradeep; Lahiri, Goutam (2010). "Biomimetic Sensor for Certain Phenols Employing a Copper(II) Complex". Analytical Chemistry 82: 5983–5992. doi:10.1021/ac1004037.
- Gadhari, Nayan; Sanghavi, Bankim; Srivastava, Ashwini (2011). "Potentiometric stripping analysis of antimony based on carbon paste electrode modified with hexathia crown ether and rice husk". Analytica Chimica Acta 703: 31–40. doi:10.1016/j.aca.2011.07.017.
- Gadhari, Nayan; Sanghavi, Bankim; Karna, Shashi; Srivastava, Ashwini (2010). "Potentiometric stripping analysis of bismuth based on carbon paste electrode modified with cryptand 2.2.1 and multiwalled carbon nanotubes". Electrochimica Acta 56: 627–635. doi:10.1016/j.electacta.2010.09.100.
- Sanghavi, Bankim; Srivastava, Ashwini (2013). "Adsorptive stripping voltammetric determination of imipramine, trimipramine and desipramine employing titanium dioxide nanoparticles and an Amberlite XAD-2 modified glassy carbon paste electrode". Analyst. doi:10.1039/C2AN36330E.
- Wang, J. (1985). Stripping Analysis: Principles, Instrumentation, and Applications, VCH Publishers, Inc., Deerfield Beach, Florida.
- http://www.academia.edu/2569163 /Potentiometric_stripping_analysis_of_methyl_and_ethyl_parathion_employing_carbon_nanoparticles_and_halloysite_nanoclay_modified_carbon_paste_electrode