Graduate
  1. Physical Chemistry  1.1. Thermodynamics  1.1.1. Laws of Thermodynamics  1.1.2. Enthalpy and heat capacity  1.1.3. Entropy and free energy  1.1.4. Phase Equilibrium  1.1.5. Statistical thermodynamics  1.1.6. Thermodynamic cycle  1.1.7. Fugacity and activity  1.2. Quantum Chemistry  1.2.1. Principles of quantum mechanics  1.2.2. Schrödinger Equation  1.2.3. Particle in a box  1.2.4. Operators and eigenvalues  1.2.5. Atomic orbitals  1.2.6. Molecular orbital theory  1.2.7. Perturbation theory  1.2.8. Valence bond theory  1.2.9. Hybridization and chemical bonding  1.3. Chemical kinetics  1.3.1. Rate laws and reaction mechanisms  1.3.2. Collision theory  1.3.3. Transition state theory  1.3.4. Enzyme Kinetics  1.3.5. Chain Reactions and Polymerization  1.3.6. Photochemical reactions  1.4. Statistical mechanics  1.4.1. Partitioning functions  1.4.2. Molecular distribution functions  1.4.3. Boltzmann Distribution  1.4.4. Bose–Einstein and Fermi–Dirac statistics  1.5. Spectroscopy  1.5.1. Rotational Spectroscopy  1.5.2. Vibrational Spectroscopy  1.5.3. Electronic Spectroscopy  1.5.4. Nuclear magnetic resonance spectroscopy  1.5.5. Mass Spectrometry  1.5.6. Raman Spectroscopy  1.5.7. Electron paramagnetic resonance spectroscopy  1.6. Surface and colloidal chemistry  1.6.1. Absorption isotherm  1.6.2. Surface tension and wetting  1.6.3. Colloidal Stability  1.6.4. Catalysis  1.6.5. Emulsions and micelles  1.7. Electrochemistry  1.7.1. Nernst equation  1.7.2. Electrochemical cells  1.7.3. Conductivity and mobility  1.7.4. War  1.7.5. Fuel cells  1.7.6. Electrolysis
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic reactions  2.2. Spectroscopy and structural determination  2.2.1. UV-Vis Spectroscopy  2.2.2. IR Spectroscopy  2.2.3. NMR Spectroscopy  2.2.4. Mass Spectrometry  2.2.5. X-ray crystallography  2.3. Stereoscopic  2.3.1. Chirality and optical activity  2.3.2. Structural analysis  2.3.3. Geometrical isomerism  2.3.4. Dynamic Stereochemistry  2.4. Organometallic Chemistry  2.4.1. Organolithium and organomagnesium reagents  2.4.2. Palladium-catalyzed cross-coupling reactions  2.4.3. Transition Metal Complexes  2.4.4. Metal–carbon bond  2.5. Polymer chemistry  2.5.1. Polymerization mechanism  2.5.2. Polymer Characteristics  2.5.3. Biodegradable Polymer  2.5.4. Conducting polymer  2.5.5. Supramolecular polymers  2.6. Medicinal chemistry  2.6.1. Drug design and development  2.6.2. Pharmacokinetics and pharmacodynamics  2.6.3. Structure-activity relationships  2.6.4. Molecular docking and drug screening
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Crystal field theory  3.1.2. Ligand field theory  3.1.3. Spectrochemical Series  3.1.4. Chelation and stability  3.2. Organometallic Chemistry  3.2.1. Metal Carbonyls  3.2.2. Catalysis by organometallic complexes  3.2.3. Metallocenes  3.3. Bio-inorganic chemistry  3.3.1. Metalloproteins and enzymes  3.3.2. The role of metals in biological systems  3.3.3. Metal ion transport and storage  3.4. Solid state chemistry  3.4.1. Crystal Structures  3.4.2. Band theory of solids  3.4.3. Superconductors  3.4.4. Defects in the crystal  3.5. Lanthanides and Actinides  3.5.1. Electronic configuration in lanthanides and actinides  3.5.2. Coordination chemistry of the lanthanides  3.5.3. Magnetic Properties of Lanthanides
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.2. Spectroscopic Techniques  4.2.1. Atomic absorption spectroscopy  4.2.2. X-ray diffraction  4.2.3. Inductively coupled plasma spectroscopy  4.3. Electroanalytical methods  4.3.1. Potentiometry  4.3.2. Voltammetry  4.3.3. Colometry  4.4. Mass Spectrometry  4.4.1. Ionization Technique  4.4.2. Fragmentation Pattern  4.5. Chemometrics  4.5.1. Multidisciplinary analysis  4.5.2. Machine Learning in Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.1.1. Force fields and energy minimization  5.1.2. Monte Carlo simulation in molecular dynamics simulations  5.2. Quantum chemical methods  5.2.1. Hartree–Fock theory  5.2.2. Density functional theory  5.2.3. Semi-empirical methods  5.3. Computational drug design  5.3.1. Molecular Docking  5.3.2. QSAR Modeling  5.3.3. Virtual Screening
  6. Biochemistry  6.1. Enzyme Kinetics  6.1.1. Michaelis-Menten kinetics  6.1.2. Inhibition mechanism  6.2. Metabolism and Bioenergetics  6.2.1. Glycolysis  6.2.2. Citric acid cycle  6.2.3. Electron transport chain  6.3. molecular Biology  6.3.1. DNA replication and repair  6.3.2. Protein synthesis  6.3.3. Gene Regulation  6.4. Structural Biochemistry  6.4.1. Protein Folding  6.4.2. Membrane Biophysics
  7. Environmental Chemistry  7.1. Atmospheric Chemistry  7.1.1. Greenhouse gases  7.1.2. Ozone depletion  7.1.3. Air pollutants and smoke  7.2. Water Chemistry  7.2.1. pH and water hardness  7.2.2. Wastewater treatment  7.2.3. Aquatic Chemistry  7.3. Soil Chemistry  7.3.1. Heavy metal contamination  7.3.2. Soil pH and Buffering  7.3.3. Nutrient cycling  7.4. Toxicology and Chemical Safety  7.4.1. Toxicokinetics  7.4.2. Risk Assessment in Toxicology and Chemical Safety in Environmental Chemistry  7.4.3. Effects of pollutants on the environment

Graduate → Analytical chemistry → Spectroscopic Techniques ↓


Atomic absorption spectroscopy


Atomic absorption spectroscopy (AAS) is an important analytical chemistry technique used to determine the concentrations of elements in a sample. Used primarily in materials, environmental or diagnostic analysis, AAS allows for accurate quantitative analysis of metals and metalloids. Understanding the principles and applications of AAS is important for chemists who are engaged in the study of various substances.

Principle of atomic absorption spectroscopy

The basic principle of AAS is based on the absorption of light by free, ground-state atoms. When atoms absorb specific wavelengths of light, transitions between electronic energy levels occur. The amount of light absorbed is directly proportional to the concentration of atoms in the light path.

Electron energy levels

An atom consists of a nucleus and electrons that are at different energy levels. In AAS, when these electrons absorb light, they move from a lower energy level to a higher energy level. The energy of the absorbed light must match the energy difference between the two levels:

e = hν = hc/λ

Where:

  • E is the absorbed energy.
  • h is the Planck constant.
  • ν is the frequency of the light.
  • c is the speed of light.
  • λ is the wavelength.

Absorption process

When a beam of light passes through the sample, atoms of a specific element absorb light at specific wavelengths. The decrease in light intensity due to absorption is measured by a detector and used to calculate the concentration of the element according to the Beer-Lambert law:

A = εlc

Where:

  • A is the absorption.
  • ε is the molar absorptivity (L mol -1 ·cm -1 ).
  • l is the path length (cm).
  • c is the concentration (mol L -1 ).

Components of atomic absorption spectroscopy

Light source(hollow cathode lamp) Chopper Atomizer (flame/furnace) Monochromator Detectors

A typical AAS instrument consists of several components, which work together to facilitate spectroscopic analysis.

Light source

The light source in AAS is usually a hollow cathode lamp (HCl), specific for the element being analyzed. The lamp emits light at the specific wavelength absorbed by the element in question.

Chopper

A chopper is used to control the light from the hollow cathode lamp, producing a pulsed signal, which increases detection sensitivity by differentiating between the signal and ambient light.

Atomizer

An atomizer, such as a flame or graphite furnace, atomizes the sample solution into free atoms. In a flame atomizer, the sample is sucked into a flame where atomization occurs.

Furnace atomization equation:
M(s) + e- → M(g)

Monochromator

The monochromator isolates the specific wavelengths of light absorbed by atoms. It removes stray light and other wavelengths, focusing only on the absorption line for analysis.

Detectors

The detector captures the light intensity and converts it into an electrical signal to measure absorption. Generally, photomultiplier tubes are used due to their sensitivity.

Applications of atomic absorption spectroscopy

AAS is widely used in various fields due to its accuracy in measuring the concentrations of elements.

Environmental analysis

AAS helps monitor trace metals in environmental samples, such as water, soil, and air. This is important in determining pollution levels and assessing environmental contamination.

Example: Measuring lead levels in drinking water.

Clinical chemistry

In clinical situations, AAS measures metal concentrations in biological samples such as blood or urine. This is important for the diagnosis and monitoring of conditions related to metal metabolism and toxicity.

Example: Determination of copper in the blood of patients with Wilson's disease.

Food and agriculture

AAS is used to ensure food safety and quality by analyzing samples for toxic metals, nutritional content, and fortification.

Example: Analysis of zinc content in agricultural fertilizers.

Benefits and limitations of AAS

Benefit

  • Highly sensitive: capable of detecting metal concentrations at the parts per million (ppm) or parts per billion (ppb) level.
  • Element specific: Minimal interference from the presence of other elements or compounds.
  • Wide application range: Applicable to solids, liquids and gases after proper sample preparation.

Boundaries

  • Single element analysis: Limited to analyzing one element at a time, multi-element analysis requires analyzing multiple times.
  • Sample preparation: Samples often require labor-intensive preparation to ensure accurate measurements.
  • Matrix effects: The presence of other materials can sometimes affect the readings, necessitating the use of matrix-matched standards.

Conclusion

Atomic absorption spectroscopy remains a fundamental tool in analytical chemistry for trace element analysis. Its specificity, sensitivity, and applicability make it indispensable in environmental, clinical, and industrial settings. While solutions to its limitations continue to be developed, AAS provides reliable and accurate quantitative analysis, playing a vital role in scientific and industrial progress.


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Atomic absorption spectroscopy

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