Instrumental analytical techniques are methods that use instruments to study the composition, structure, and properties of substances. They are broadly classified based on the type of interaction they use: spectroscopy, chromatography, electrochemistry, and mass-based methods.
Here’s a overview of the main types:
1. Spectroscopic Techniques
These methods study the interaction of matter with electromagnetic radiation.
- UV-Visible Spectroscopy (UV-Vis): Measures absorption of UV or visible light. Used to determine concentration and study conjugated systems.
- Infrared Spectroscopy (IR): Measures absorption of infrared light. Identifies functional groups in molecules.
- Nuclear Magnetic Resonance (NMR): Uses magnetic fields to study nuclei (like ¹H and ¹³C). Provides structural information.
- Fluorescence Spectroscopy: Measures emitted light from excited molecules. Used in trace detection and bioanalysis.
- Atomic Absorption Spectroscopy (AAS): Measures absorption by metal atoms. Used for metal analysis in samples.
2. Chromatographic Techniques
These methods separate components in a mixture based on their physical or chemical properties.
- Gas Chromatography (GC): Separates volatile compounds. Used for environmental and forensic analysis.
- High-Performance Liquid Chromatography (HPLC): Separates non-volatile compounds. Used in pharmaceuticals and biochemistry.
- Thin Layer Chromatography (TLC): Quick, simple separation for qualitative analysis.
- Ion Chromatography (IC): Separates ions and polar molecules.
3. Mass-Based Techniques
These methods analyze molecules based on their mass-to-charge ratio.
- Mass Spectrometry (MS): Provides molecular weight and structural information. Often combined with GC or HPLC (GC-MS, LC-MS).
- Electron Microscopy (EM): Visualizes materials at very high magnification; can also provide elemental composition (with EDX).
4. Electrochemical Techniques
These methods measure electrical properties to analyze substances.
- Potentiometry: Measures voltage to determine ion concentration (example: pH meter).
- Voltammetry / Amperometry: Measures current as a function of applied voltage. Used in trace metal or biomolecule detection.
- Conductometry: Measures electrical conductivity to study ionic solutions.
5. Thermal and Physical Techniques
These methods study physical changes in materials.
- Thermogravimetric Analysis (TGA): Measures weight change with temperature.
- Differential Scanning Calorimetry (DSC): Measures heat flow to study phase transitions.
- X-ray Diffraction (XRD): Determines crystalline structure of solids.
In Short
Instrumental analytical techniques can be classified as spectroscopic, chromatographic, mass-based, electrochemical, and thermal/physical methods. Each type provides specific information about the composition, structure, or properties of a substance.