## Polarography and Ilkovic equation

### What is Polarography?

- Polarography is an electrochemical technique used to measure the concentration of certain substances in a sample.
- It is based on the principle of electrochemical reduction and oxidation reactions that occur at an electrode surface.
- In polarography, a sample is placed in a cell containing an electrolyte solution and two electrodes: a working electrode and a reference electrode.
- A potential is applied between the electrodes, and the current passing through the cell is measured as a function of the applied potential.
- As the potential is varied, different electrochemical reactions occur at the working electrode, leading to changes in the current.
- The current-potential curve obtained in polarography is called a polarogram.
- By analyzing the shape and position of the polarogram, it is possible to determine the concentration of the substance of interest in the sample.
- Polarography is a versatile and widely used technique in analytical chemistry, and it has applications in various fields, including environmental monitoring, pharmaceutical analysis, and industrial quality control.
- It is particularly useful for measuring the concentration of substances that undergo electrochemical reactions, such as metal ions, organic compounds, and dissolved gases.

## The Ilkovic equation

- Ilkovic equation relates the
**diffusion current (id)**measured in polarography to the**concentration (C)**of the electroactive species in the electrolyte solution. It is named after**Dionýz Ilkovič**, a Slovak chemist, who derived the equation in 1934.

Here’s the formula for the Ilkovic equation:

id = 607nFDm^(1/2)t^(1/2)C

where:

**id**: Diffusion current (in amperes, A)**n**: Number of electrons transferred in the electrode reaction (dimensionless)**F**: Faraday constant (96485 C/mol)**D**: Diffusion coefficient of the electroactive species (in cm²/s)**m**: Mass flow rate of the mercury electrode (in mg/s)**t**: Drop time of the mercury electrode (in seconds)**C**: Concentration of the electroactive species (in mmol/L)

**Understanding the terms:**

**Diffusion current:**The current measured in polarography that arises due to the diffusion of the electroactive species towards the electrode surface.**n**: The number of electrons involved in the reduction or oxidation reaction occurring at the electrode.**F**: A constant value representing the amount of charge per mole of electrons.**D**: A measure of how quickly the electroactive species can move through the solution.**m**: The rate at which mercury flows from the capillary tip forming the dropping mercury electrode (DME).**t**: The time it takes for a mercury drop to fall from the DME.**C**: The concentration of the electroactive species in the solution.

**Interpretation:**

The Ilkovic equation shows that the diffusion current is proportional to:

- The square root of the diffusion coefficient (D) and the drop time (t) – This indicates that the current increases as the diffusion rate and the time available for diffusion increase.
- The number of electrons transferred (n) – More electrons transferred per molecule lead to a higher current.
- The concentration of the electroactive species (C) – Higher concentrations lead to more molecules available for the reaction, resulting in a larger current.

**Applications **of Polarography and Ilkovic equation

The Ilkovic equation has various applications in analytical chemistry, including:

**Quantitative analysis:**Determining the concentration of electroactive species in a solution by measuring the diffusion current.**Characterizing electrode reactions:**Understanding the number of electrons involved in the reaction and the rate of electron transfer.**Studying reaction mechanisms:**Investigating the role of diffusion and other parameters in the overall reaction process.

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