Instrumental Analysis Lecture 4

Study Notes

Spectroscopy involves studying interactions between matter and electromagnetic radiation; when quantitative analysis is applied, it is referred to as spectrometry.
Atomic spectroscopy techniques include Atomic Absorption Spectroscopy (AAS), Atomic Emission Spectroscopy (AES), Atomic Fluorescence Spectroscopy (AFS), X-ray Fluorescence (XRF), and Inorganic Mass Spectroscopy (MS).

Every element has a unique atomic structure with a positively charged nucleus surrounded by electrons necessary for neutrality.
Electrons occupy energy orbitals and can transition to higher energy levels by absorbing energy from collisions, light, or high-energy electrons.
Low energy ground state (E0) and excited states (E′’) depend on electron transitions driven by acquired energy (ΔE).
Specific light wavelengths entering an analytical system cause electron excitation, reducing the transmitted light amount, characteristic of AAS.

In AAS, light absorption leads to a decrease in transmitted light.
In AES, excited outer shell electrons emit light when returning to the ground state.
AFS involves ground state atoms absorbing and later emitting light.

Atomization, converting samples into vapor, is fundamental for emission, absorption, and fluorescence techniques.
Critical components include atomization sources, sample introduction devices, and spectrometers for wavelength selection and light detection.

Atomization involves:
- Solvent removal
- Separation of analyte from ions and matrix
- Reduction to ground state atoms
Atomization technology typically uses flames and electrothermal devices which provide quick measurements with minimal interference.

Light sources are classified into continuous (broadband) and line sources; continuous sources emit over a range of wavelengths, while line sources emit at specific wavelengths.
Common lamps used as light sources include various types that provide specific atomic lines needed for analysis.

Flame atomizers consist of components like a pneumatic nebulizer, expansion chamber, and an air-acetylene flame.
Suitable for AAS and AFS due to straightforward operation; can typically measure concentrations around 1 μg/ml (ppm).
Advances are being made to improve nebulizer efficiency and achieve 100% atomization, allowing for pulsed sample flow instead of continuous flow.