Polarography: A voltammetry technique using a dropping mercury electrode
1. 1
Polarography
BY
Dr. Suman Pattanayak
Associate Professor
Department of Pharma Analysis & QA.
Vijaya Institute of Pharmaceutical Sciences for Women
M. Pharm/ I Sem
Advance Pharmaceutical Analysis
2. Polarography is a subclass of
voltammetry where the working
electrode is a dropping mercury
electrode (DME).
It is current versus potential are recorded
when gradual changing current is take
place when current applied to cell.
3. A cell containing :
ï‚— Solution of interest (electroactive
substance)
ï‚— Stable reference electrode. e.g : calomel
electrode.
ï‚— Small area of indicator electrode (DME)
ï‚— Auxiliary or counter electrode .
5. ï‚— Hg will dropped in stable flow rate 5- 30
drops/min.
 Volts applied 50 – 200 mv/min
 Drop life 2 – 12 sec.
 Potential range (+ 0.4) – (-2) V
6. Advantage of Hg electrode
ï‚— As the Hg capillary very narrow so, able to
analyse very small volume of analyte.
ï‚— Surface of electrode is very reproducible .
ï‚— Surface area of electrode can be calculated
from the weight of drops.
10. Factors affecting diffusion
current
(Ilkovic equation)
ίd = 708 n C D½ m ⅔ t⅙
ï‚— n : change in valency
ï‚— C : concentration
ï‚— D : diffusion coefficient.
ï‚— m: flow rate of mercury dropping.
ï‚— t : life time of mercury drop.