Steps
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)
Read more about this topic: Anodic Stripping Voltammetry
Famous quotes containing the word steps:
“All our steps are ordered by the LORD; how then can we understand our own ways?”
—Bible: Hebrew, Proverbs 20:24.
“There must be a solemn and terrible aloneness that comes over the child as he takes those first independent steps. All this is lost to memory and we can only reconstruct it through analogies in later life....To the child who takes his first steps and finds himself walking alone, this moment must bring the first sharp sense of the uniqueness and separateness of his body and his person, the discovery of the solitary self.”
—Selma H. Fraiberg (20th century)
“Every child has an inner timetable for growth—a pattern unique to him. . . . Growth is not steady, forward, upward progression. It is instead a switchback trail; three steps forward, two back, one around the bushes, and a few simply standing, before another forward leap.”
—Dorothy Corkville Briggs (20th century)