What is Polarogram in polarography?
What is Polarogram in polarography?
(pŏl′ē-grăm) [″ + gramma, something written] A tracing or record made by a polygraph.
What is limiting current in polarography?
The limiting current is the sum of the residual and the diffusion currents. The residual current is subtracted from the limiting current to give the wave height. When the current is measured only at the end of the drop life, the technique is termed sampled dc polarography.
Why oxygen is removed in polarography?
WHY? Polarography is a highly sensitive technique for detecting and determining electroactive substances. Since it can be present in solutions in high concentrations and since it is electroactive, oxygen must be removed from the analyte prior to polarographic analysis.
How are polarographic curves plotted?
The analytical data for a voltammetric experiment is depicted in the form of a voltammogram (a polarogram in case of polarography) which plots the current produced by the electrolyte vs. A current-voltage curve is constructed by applying a series of potential steps when each step is synchronized with the drop fall.
What is potentiometry chemistry?
Potentiometry is one of the methods of electroanalytical chemistry. It is usually employed to find the concentration of a solute in solution. In potentiometric measurements, the potential between two electrodes is measured using a high impedance voltmeter.
What is migration current?
[mī′grā·shən ‚kə·rənt] (physical chemistry) Additional current produced by electrostatic attraction of cations to the surface of a dropping electrode; an unpredictable and undesirable effect to be avoided during analytical voltammetry.
What is half wave potential?
Half-wave potential (E1/2) is a potential at which polarographic wave current is equal to one half of diffusion current (id). Observation of a current peak at a specific half-wave potential therefore identifies the chemical species producing the current.
What is used as cathode in polarography?
INTRODUCTION. Polarography is an electrolysis technique in which microelectrolysis is performed at a dropping mercury electrode (DME) in an unstirred solution. In the former, the working electrode (DME) is made the cathode while in the latter, it is the anode.
How can a Polari minimize Maxima?
Maxima, frequently observed on polarographic waves due to the reduction or oxidation of cations, anions or neutral molecules thus interferring with analyte quantification, are usually suppressed by the addition of minute amounts of an appropriate surfacc-active agent.
Why gelatin is used in polarography?
Decreases viscosity of the solution. Eliminates migrating current.
Why mercury is used in DME?
The pool of mercury acts as a counter electrode, i.e., anode if DME is the cathode or cathode if DME is the anode. The counter electrode is a non-polarisable electrode. To the analyte solution, an electrolyte like KCl is added i.e., 50-100 times of sample concentration.
What is polarographic analysis?
polarography, also called polarographic analysis, or voltammetry, in analytic chemistry, an electrochemical method of analyzing solutions of reducible or oxidizable substances. Polarography is also used to identify numerous types of organic compounds and to study chemical equilibria and rates of reactions in solutions.
What is the use of polarography in chemistry?
Polarography is probably the only dynamic (electrolytic) electroanalytical technique that can be conveniently and reliably applied for the determination of a wide spectrum of organic compounds. Polarography was first developed by Heyrovsky in 1922.
When was the first polarograph invented?
In 1925, Heyrovsky and Shikata constructed the polarograph, a device that automatically records current–potential curves. The polarograph was probably the first automatic apparatus to be applied in analytical chemistry.
What is alternating current (ac) polarography?
The alternating current (AC) polarographic techniques are derived from direct current (DC) polarography as described above by imposing a small perturbation voltage of various frequencies upon the main DC polarizing voltage. These methods chiefly detect the adsorption of the participants of the electrode processes.
What is differentdifferential pulse polarography?
Differential pulse polarography is a polarographic technique that use a series of discrete potential steps rather than a linear potential ramp to obtained the experimental polarogram The differential current is plotted vs. the average potential to obtain the differential pulse polarogram, NORMAL PULSE POLAROGRAPHY
