Trace element analysis in microanalysis involves detecting and quantifying very small amounts of elements (often at parts-per-million or parts-per-billion levels) in samples. This is important in environmental, pharmaceutical, and material studies.
Steps in Trace Element Analysis
- Sample Collection and Preparation
- Collect the sample carefully to avoid contamination.
- Prepare the sample: solid samples may be digested using acids; liquid samples may be filtered or concentrated.
- Selection of Analytical Technique
- Choice depends on element type, required sensitivity, and sample size.
Common Techniques Used
- Atomic Absorption Spectroscopy (AAS)
- Measures the absorption of light by free atoms of the element.
- Graphite Furnace AAS (GFAAS) is used for ultra-trace analysis.
- Inductively Coupled Plasma Techniques
- ICP-OES (Optical Emission Spectroscopy): Detects multiple elements simultaneously.
- ICP-MS (Mass Spectrometry): Highly sensitive, can detect elements at parts-per-trillion levels.
- X-ray Fluorescence (XRF)
- Non-destructive technique for solids and powders.
- Detects characteristic X-rays emitted by elements in the sample.
- Neutron Activation Analysis (NAA)
- Sample is irradiated with neutrons, producing radioactive isotopes.
- Measures emitted gamma rays to identify and quantify elements.
- Electrochemical Methods
- Techniques like Anodic Stripping Voltammetry detect trace metals in water.
Key Considerations in Trace Element Analysis
- Avoiding contamination: Trace levels are easily affected by dust, containers, or reagents.
- Calibration and standards: Use standard solutions for accurate quantification.
- Sensitivity and detection limit: Choose techniques capable of detecting very low concentrations.
In short:
Trace element analysis in microanalysis involves careful sample preparation and the use of sensitive techniques like AAS, ICP-MS, XRF, or NAA to detect and quantify elements present in very small amounts.