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 → Physical Chemistry → Spectroscopy and molecular structure ↓


Mass Spectrometry


Mass spectrometry is a powerful analytical technique used to measure the mass-to-charge ratio of ions. It provides information about the molecular structure and composition of compounds, making it an invaluable tool in the field of physical chemistry. This method helps to identify unknown substances, determine the isotopic composition of the elements in a molecule, and elucidate the structure of complex compounds.

Introduction to mass spectrometry

The basic principle of mass spectrometry is straightforward. A sample is ionized, and the ions produced are separated based on their mass-to-charge ratio (m/z). The detector then records these ions, and the resulting mass spectrum displays the abundance of the detected ions as a function of the mass-to-charge ratio.

This process can be divided into several stages:

  • Ionization: generating ions from the sample.
  • Acceleration: The ions are accelerated by means of an electric field.
  • Deflection: The ions are deflected by the magnetic field.
  • Detection: Ions are detected, and data are recorded to produce a mass spectrum.

Ionization technique

Various ionization techniques are used in mass spectrometry, each of which is suitable for different types of compounds:

Electron ionization (EI)

    m + e⁻ → m⁺ + 2e⁻

In electron ionization, an electron beam is used to bombard sample molecules, causing them to lose an electron and form positive ions. EI is a harsh ionization technique that often results in extensive fragmentation.

Chemical ionization (CI)

    M + reagent⁺ → [M+H]⁺ + fragment

Chemical ionization involves ion-molecule reactions in the gas phase. First a reagent gas (such as methane) is ionized, which then ionizes the molecules of the sample. CI is a gentler technique than EI, often resulting in intact molecular ions.

Electrospray ionization (ESI)

Electrospray ionization is widely used for polar and large biomolecules. The sample is dissolved in a solvent and sprayed through a charged needle, forming a fine mist. Solvent evaporation yields charged droplets that eventually result in bare ions.

Mass analyzer

Mass analyzers separate ions based on their mass-to-charge ratio. Various types of analyzers have been developed, each with its own applications and strengths:

Quadrupole mass analyzer

Quadrupole mass analyzers use oscillating electric fields to selectively filter ions. Only ions with a specific mass-to-charge ratio pass through the detector. Quadrupole analyzers are ideal for routine quantitative analysis because of their robustness and simplicity.

Time-of-flight (TOF) mass analyzer

In a TOF mass analyzer, ions are accelerated and allowed to flow through a tube. Ions of different m/z ratios reach the detector at different times. TOF analyzers provide high mass accuracy and are useful for large biomolecules.

Magnetic sector mass analyzer

Magnetic sector analyzers use magnetic fields to separate ions based on their speed. These types of analyzers provide high mass resolution and are often used in high precision applications.

Detectors

Once separated, the ions are detected by a detector that measures the intensity of each ion beam. The most common types of detectors are:

  • Faraday cup: A simple collector of ions that measures the current induced by the ions falling on it. Suitable for large currents.
  • Electron multiplier: An amplifier that detects low ion currents by generating cascading electrons.
  • Microchannel plate (MCP): Amplifies ion signals for high speed and high sensitivity requirements.

Case study: Interpreting the mass spectrum

Consider the mass spectrum of ethanol (C 2 H 5 OH). Prominent peaks may include:

  • m/z = 46: Molecular ion peak represents C 2 H 5 OH⁺.
  • m/z = 31: Represents the ion CH2OH⁺.
  • m/z = 29: Corresponds to the ion C 2 H 5 ⁺.
  • m/z = 28: Indicates the carbon monoxide (CO⁺) fraction.

Interpreting mass spectra involves understanding the fragmentation patterns which help in understanding the structure of the compound.

Applications of mass spectrometry

The versatility of mass spectrometry makes it valuable in many areas:

Proteomics

Mass spectrometry is essential in identifying and quantifying proteins in complex biological samples, aiding in biomarker discovery and understanding disease mechanisms.

Metabolomics

This technique identifies metabolites within biological systems, and provides information about disease conditions, drug responses, and metabolic pathways.

Environmental analysis

Mass spectrometry detects pollutants in the environment at a microscopic level, ensuring compliance with health regulations.

Forensic science

It is used to identify substances in drug testing, toxicology, and criminal investigations.

The future of mass spectrometry

Advances in ionization techniques, mass analyzers, and detectors have continued to expand the applications and capabilities of mass spectrometry, improving sensitivity, precision, and speed, with a dramatic impact on research and industry.


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Mass Spectrometry

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