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 ↓


Colometry


Coulometry is an electrochemical technique used to determine the amount of a substance transformed during an electrochemical reaction. Named after Charles-Augustin de Coulomb, this method relies on the measurement of electricity consumed or produced (charge in coulombs). In this overview of coulometry, we will understand its basic principles, instruments, applications, and advantages.

Principles of colometry

The main idea of coulometry is based on Faraday's laws of electrolysis, which relate the amount of a substance converted at the electrode to the amount of electric charge passed through the solution. The basic equation governing this relation is:

m = (Q x M) / (nx F)

Where:

  • m = mass of the substance converted (in grams)
  • Q = total electric charge (coulomb)
  • M = molar mass of the substance (grams per mole)
  • n = number of electrons exchanged per molecule of the substance
  • F = Faraday constant (about 96485 C/mol)

To put this into perspective, let's visualize this process with a simple electrochemical cell:

Anode Cathode Electrolyte

In the diagram above, the electric charge flows from the anode to the cathode through the electrolyte solution. By integrating the current over the time period of the reaction, we can calculate the total charge (Q).

Types of colometry

There are two main types of coulometry: potentiostatic coulometry (also called controlled potential coulometry) and amperostatic coulometry (also called controlled current coulometry).

Potentiostatic colometry

In potentiostatic coulometry, a constant potential is applied to the electrochemical cell. The distinct advantage of this method is that the selectivity of the measurement can be controlled by strictly maintaining the potential only when the desired reaction occurs.

Current (I) = dQ/dt

This equation of current (I) shows how the charge (Q) changes with time (t). Integration of the current over time gives the total charge used for the transformation of the analyzer.

Emperostatic colometry

In amperostatic coulometry, a constant current is applied. This method is generally faster because it ensures a quick reaction rate. The total time required for the reaction to complete is used to calculate the respective charge passed, and hence, the amount of analyte.

Equipment

The basic setup for colometric measurements includes:

  • Power supply: To control potential or current.
  • Electrochemical cell: It consists of working, reference and counter electrodes.
  • Analytical balance: For weighing samples before and after electrolysis.
  • Data acquisition system: To record current and potential data over time.

Stages of colometric analysis

Here is the general procedure for a typical colometric analysis:

  1. Prepare the electrochemical cell by properly placing the analyte solution and the electrodes.
  2. Set the desired potential (for potentiostatic) or current (for amperostatic).
  3. Initiate electrolysis and record the current time data.
  4. Calculate the total charge passed using numerical integration (e.g., trapezoidal rule).
  5. Use the Faraday equation to determine the amount of reacted analyte.

Applications of colometry

Coulometry is widely used in various areas of analytical chemistry due to its accuracy and precision. Some common applications include:

  • Determination of water content: Karl Fischer coulometry specifically measures the water content in samples.
  • Metallurgical analysis: Determination of the minute quantities of metals such as copper, nickel and zinc in alloys.
  • Pharmaceuticals: Determination of active pharmaceutical ingredient concentrations.
  • Environmental analysis: Measuring pollutant ions in water bodies.

Benefits and limitations

Benefit

  • High Precision: Direct measurement of charge leads to high precision and accuracy.
  • Low detection limit: Able to detect very low concentrations of substances.
  • Minimal sample preparation required: Simple sample preparation compared to other analytical techniques.

Boundaries

  • Time consuming: Responses can take a long time, especially in the potentiostatic mode.
  • Equipment costs: Initial setup and maintenance can be expensive.
  • Selectivity: Sometimes selectivity can be a problem, especially in complex mixtures.

Conclusion

Coulometry stands out as an important analytical technique that provides accurate measurement of substances based on the fundamentals of electrochemistry. Its development has led to improvements that have paved the way for advanced applications in environmental, pharmaceutical, and industrial fields. With improvements in technology, coulometry remains a cornerstone technique in determining the structure and concentrations of various chemical entities.


PHD → 4.2.3


U
username
0%
completed in PHD

← Prev (4.2.2)
Conductometry and potentiometry
Next (4.3) →
Spectroscopic Methods

Comments 



Colometry

https://www.chemistryelite.com/phd/4.2.3?ceal=en