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 → Spectroscopic Methods ↓


Atomic absorption spectroscopy


Atomic absorption spectroscopy (AAS) is a technique used in analytical chemistry to determine the concentration of a particular element in a sample. It uses the principles of spectrophotometry, which deals with the study and measurement of radiant energy. AAS is based on the absorption of light (photons) by free, ground-state atoms. The technique is widely applied due to its high sensitivity and selectivity, making possible the quantitative determination of metals and metalloids at trace levels.

Principles of atomic absorption spectroscopy

The basic principle of AAS is related to the absorption of light by free atoms. When a sample containing metal ions is put into a flame or furnace, the energy released from the flame converts these metal ions into free atoms. These atoms can absorb light of a specific wavelength that is characteristic of that element. The amount of light absorbed at this wavelength is directly proportional to the concentration of the element in the sample.

Key components of AAS

  • Light source: AAS uses a light source, usually a hollow cathode lamp, that emits light at the specific wavelength of the element of interest.
  • Atomizers: In AAS, samples are atomized using a flame or electrothermal atomizer. In a flame atomizer, the sample is sucked into a flame where it is converted into free atoms. In electrothermal atomization, a small amount of the sample is vaporized on a graphite surface.
  • Monochromator: A monochromator isolates specific wavelengths of light absorbed by atoms.
  • Detector: The light emitted from the atomizer passes through the monochromator and is eventually detected. The detector measures the light intensity before and after the atomization process to determine the amount of light absorbed.
  • Data processing unit: This unit processes the signal from the detector to display the concentration of the element in the sample.

Simplified chemical equations

        M(g) + photon → M*(g)

where M(g) represents the free ground state atom, photon is a unit of light energy, and M*(g) is the excited state atom.

The working system of AAS

The step-by-step procedure of atomic absorption spectroscopy is as follows:

  1. The sample solution is sucked into the flame or injected into the electrothermal chamber.
  2. The heat from the flame or furnace breaks down the elements in the sample into free atoms.
  3. Light from a hollow cathode lamp passes through the atomized sample. Each element in the sample absorbs light at a specific wavelength corresponding to its electronic transition.
  4. The monochromator selects light of specific wavelengths absorbed by the sample and directs it to the detector.
  5. The detector measures the difference in light intensity before and after it passes through the sample, revealing the amount of light absorbed by the atoms, which is then related to the concentration of the element.

Advantages of atomic absorption spectroscopy

  • High sensitivity: AAS can detect concentrations of elements at the parts per million (ppm) or even parts per billion (ppb) level.
  • Selectivity: This technique can be highly selective for specific elements when appropriate light sources and atomization conditions are used.
  • Minimal sample preparation: Often, minimal sample preparation is required compared to other analytical techniques, making AAS relatively simple to use.
  • Widely applicable: AAS is particularly useful for analyzing metals and some non-metals in a variety of samples such as water, soil, and biological tissues.

Applications of atomic absorption spectroscopy

AAS is used in various fields, such as environmental analysis, clinical diagnostics, pharmaceuticals, and for trace element analysis in the food industry.

Environmental analysis

AAS is commonly used to monitor metals in environmental samples, such as water, soil, and air. Metals such as lead, mercury, cadmium, and arsenic are harmful pollutants, and their levels need to be regularly monitored to ensure public safety.

Clinical diagnosis

In medical and diagnostic applications, AAS are used to determine trace elements in biological samples such as blood and urine. This is important for diagnosing deficiencies or excesses of essential elements such as calcium, iron, and magnesium.

Food & beverage industry

The food and beverage industry uses AAS to ensure food safety by analyzing metal content. Elements such as lead and arsenic must be present below certain levels in consumable products.

Medicines

AAS is important in the pharmaceutical industry to ensure that drug products comply with specifications regarding metal impurities.

Limitations of atomic absorption spectroscopy

Despite their benefits, AAS also have some limitations:

  • Single element analysis: AAS typically allows analysis of one element at a time, which can be time consuming for samples containing multiple elements.
  • Interference: Chemical and spectral interference can affect the accuracy of AAS results. Techniques such as using matrix modifiers or background correction methods are used to overcome these issues.
  • Limited to metals: This technique is mostly limited to metallic elements. Non-metallic analysis is possible, but requires additional techniques.

Visual explanations

light source atomizer Monochromator Detectors

Conclusion

Atomic absorption spectroscopy is an important tool in analytical chemistry for the accurate determination of metal concentrations. It offers a high degree of sensitivity and selectivity, making it suitable for a wide range of applications. However, users must be alert to potential interferences and the limitation of analyzing one element at a time. With advances in technology, new methods and instruments continue to improve the efficiency and capabilities of AAS, allowing for more complex analyses and applications.


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Atomic absorption spectroscopy

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