PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Analytical chemistry → Electroanalytical techniques ↓


Voltammetry and Polarography


Electroanalytical techniques are a branch of analytical chemistry that deals with the study of chemical properties and reactions by measuring electrical properties. The two major techniques under this domain are voltammetry and polarography. These techniques are invaluable for understanding the electrochemical behavior of analytes, which are chemical species of interest. This lesson covers both techniques in great detail.

Voltammetry

Voltammetry is a category of electroanalytical method used to study various electrochemical properties of an analyte. This technique involves changing the potential of a working electrode and measuring the resulting current. Data obtained from voltammetry experiments can provide valuable information about the concentration, redox potential, and kinetic parameters of the analyte.

Basic principles

  • In voltammetry, an electrochemical cell is set up with at least two electrodes: a working electrode, where the intended reaction occurs, and a reference electrode, which maintains a constant potential.
  • Often a counter electrode is also included to complete the circuit.
  • The potential of the working electrode is varied linearly with time and the current is measured.

The usual experiment involves scanning the potential from the initial value to the final value at a constant rate and measuring the current as a function of potential. The resulting plot is called a voltammogram.

Applications of voltammetry

Voltammetry is used in a wide variety of applications, including:

  • Analysis of metal ions.
  • Detection of organic compounds.
  • To study enzyme activity.

Types of voltammetry

There are several variants of the voltammetric technique, each with unique modifications to the general setup:

Linear sweep voltammetry (LSV)

In LSV, the potential increases or decreases linearly with time. The shape of the current versus potential curve provides information about the electrochemical processes occurring at the electrode surface.


dE/dt = constant

This decision in modulation helps in analyzing fast electron transfer processes.

Cyclic voltammetry (CV)

In cyclic voltammetry, the potential sweep is applied in the forward direction and then brought back to the initial potential.


E_initial -> E_final -> E_initial

The result is a cyclic voltammogram that reveals redox reactions and coupled chemical reactions.

Cyclic voltammogramPossibilitycurrent

The shape of these peaks gives us information about the reversibility of electrochemical reactions, the number of electrons involved, and kinetic information.

Polarography

Polarography is a specific type of voltammetry using a dropping mercury electrode (DME) or static mercury drop electrode (SMDE) as the working electrode. This technique was invented by Jaroslav Heyrovský, who was awarded the Nobel Prize in Chemistry in 1959 for his invention.

Principles of polarography

  • Polarography involves applying a potential to a mercury electrode that is continuously dripped and recording the current response during the redox transformation of the analyte.
  • The potential is usually applied in a stepwise manner rather than a linear manner.

The resulting polarogram shows step-like waves, with each wave corresponding to a different electrochemical process.

PossibilitycurrentPolarogram

Benefits of polarography

Polarography is beneficial for the following reasons:

  • High sensitivity to various chemical species.
  • Ability to analyze complex mixtures.
  • Ability to provide both qualitative and quantitative data.

Boundaries

Despite its many advantages, polarography has some limitations, such as:

  • Analysis time is relatively slow due to the use of a falling mercury electrode.
  • Hard with substances that form insoluble mercury compounds.

Applications of polarography

Polarographic techniques are useful in a number of areas:

  1. Environmental chemistry for heavy metal analysis.
  2. Biological studies to explore enzyme kinetics and drug interactions.
  3. For the detection of metals and other substances in food chemistry.

Comparison and conclusion

Both voltammetry and polarography are powerful techniques in electroanalytical chemistry, each with its own unique strengths. The choice of either one depends largely on the specific requirements of the analysis, such as the nature of the analyte, the required sensitivity, and the availability of equipment.

Voltammetry offers a broad range of electrode materials and configurations, making it highly versatile. Polarography, with its distinctive mercury electrode, particularly excels at trace metal analysis and can exploit the unique properties of mercury to provide detailed electroanalytical insights. Understanding these techniques and their nuances better equips chemists and researchers to select the appropriate method for their specific analytical needs.


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Voltammetry and Polarography

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