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 → Chromatography ↓


Ion Chromatography


Ion chromatography, also known as IC, is a powerful analytical technique used primarily for the separation and quantification of ions present in a solution. It is a form of liquid chromatography that takes advantage of differences in ion exchange affinity to achieve separation.

Principle of ion chromatography

The basic principle of ion chromatography revolves around the separation of ionic species by means of ion exchange resins. These resins are typically made of organic polymers containing attached functional groups capable of reversible covalent bonding with ions.

For example, a cation exchange resin contains negatively charged functional groups, such as sulfonate groups (R-SO 3 -), which interact with positively charged cations. In contrast, an anion exchange resin contains positively charged groups, such as quaternary ammonium groups (R-NH 3 +), which interact with anions.

Chemical interactions in ion chromatography

Consider a simplified representation of the exchange process for cation exchange resins:

R-SO 3 ^- Na + (resin) + K + (solution) ⇌ R-SO 3 ^- K + (resin) + Na + (solution)

In this case the resin will prefer to bind potassium ions (K +) from the solution, and leave sodium ions (Na +) in the solution.

Components of ion chromatography

Mobile phase

The mobile phase in ion chromatography is typically a liquid that flows through the column, carrying the sample with it. This phase is responsible for transporting ions through the system and can be water or a buffered solution. Due to the sensitivity of the system, the choice of buffer and its ionic strength is important to maintain a stable environment for separation.

Stationary phase

The stationary phase is the ion exchange resin contained within the column. The selection of the resin is determined by the type of ions to be separated. As mentioned earlier, cation exchangers contain negatively charged groups and are used to separate positive ions, while anion exchangers are used for negative ions.

Detectors

After the ions are separated in the column, they are detected to provide quantitative data. Common methods of detection in ion chromatography include conductivity detection, UV/Vis detection, and sometimes more specialized methods such as mass spectrometry, depending on the use case.

Types of ion chromatography

1. Suppressed ion chromatography

In suppressive ion chromatography, the sensitivity of detection is increased by reducing the ionic background noise of the mobile phase. This is accomplished by using a suppressive device that reduces the conductivity of the eluent while leaving the signal of the analyte unaffected.

2. Non-suppressed ion chromatography

Non-suppressed ion chromatography is simpler in the instrumentation because it does not involve a suppression step. However, it may be less sensitive to some ions due to higher levels of background conductivity.

Applications of ion chromatography

Ion chromatography is widely used in various fields including environmental analysis, pharmaceuticals, food and beverage testing.

Environmental analysis

IC is used extensively to detect and measure the concentration of ions in environmental samples. For example, it can detect nitrate and phosphate levels in water bodies, which are important indicators of pollution.

NO 3 - + water sample ⇌ NO 3 - (bonded on resin)

Medicines

In the pharmaceutical industry, IC can be used to determine the purity of drugs by analyzing their ionic components. It can analyze counter-ions and possible impurities, ensuring the quality of pharmaceutical products.

Food & Beverage industry

This technique is used to assess the concentration of additives and nutrients in food products. An example of this would be determining acidity regulators such as phosphate and citrate in soft drinks.

Advantages of ion chromatography

Ion chromatography is a robust and versatile technique that offers many advantages:

  • High sensitivity: This technique can detect ions at very low concentrations.
  • Versatility: Capable of analyzing both cations and anions.
  • Quantitative: Provides accurate and precise quantification of ions.
  • Non-destructive: Samples can often be recovered after analysis.
  • Automation: IC systems can be easily automated for high-throughput analysis.

Limitations of ion chromatography

Despite its advantages, ion chromatography also has limitations:

  • Complex setup: Careful selection of resins and mobile phases is required for optimal performance.
  • Cost: Initial setup and maintenance costs can be high.
  • Specificity: Pretreatment may be required to remove interference from other ions.

Future directions

The future of ion chromatography looks promising, as research continues to focus on improving sensitivity, reducing analysis times, and increasing automated processes. Additionally, the development of new detectors and columns continues to expand the applications of ICs in a variety of scientific fields.

In conclusion, ion chromatography stands as an important tool in analytical chemistry, providing crucial insights into the ionic composition of diverse samples. As advances continue, both its efficiency and range of applications are expected to grow, meeting more complex analytical demands.


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Ion Chromatography

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