AAS instruments detect and quantify metallic elements using the following key components:
1) Source:
Hollow Cathode Lamp (HCL): Emits element-specific radiation via metal ions in the lamp returning to their ground state.
Electrodeless Discharge Lamp (EDL): Used for difficult elements, emitting radiation via excitation of gaseous elements with microwave or radiofrequency energy.
2) Atomizer:
Flame Atomizer: Nebulizes the sample into a mist introduced into a flame for atomization (commonly using acetylene-air or acetylene-nitrous oxide flames).
Graphite Furnace Atomizer: Heats small sample volumes in stages to atomize analytes.
3) Monochromator:
Isolates the specific wavelength absorbed by the analyte, filtering out unwanted radiation.
4) Detector:
Photomultiplier tube (PMT) measures the decrease in light intensity due to analyte absorption, converting it into an electrical signal.
5) Output Device:
Processes and displays data as a digital readout or graph; often connected to computers for analysis and storage.
6) Flame Control System:
Maintains a stable flame by regulating fuel and oxidant gas flow.
Process Overview:
Light from the source passes through the atomized sample, where analyte atoms absorb specific wavelengths.
The monochromator isolates this wavelength, and the PMT detects the absorption.
The light intensity reduction corresponds to the analyte's concentration.