Atomic Absorption Flashcards
Pharmaceutical application of Atomic absorption
- Used to detect metal residues remainingh from the manufacturing process in drugs
- Used to measure:
1. Zn content of insulin
2. Fe in blood or tablets
3. Heavy metals (Hg, Cd) in drinking water
4. Cu or Mn in tonics
What is the difference between atomic absorption and atomic emission
- Atomic emission uses energy from the flame to excite the electron to the excited state. This then relaxes back to the ground state giving off the photon of light.
Atomic absorption uses a light source of a specific wavelength to cause the electron to be promoted to the excited state. The flame is only used to atomise the sample. The amount of this light absorbed is then measured.
What is the primary light source used in Atomic Absorption Spectroscopy?
Hollow Cathode Lamp (HCL)
What is a Hollow Cathode Lamp (HCL)?
A HCL is a lamp that contains a cathode made from the same element being analyzed in the AA instrument.
How does a Hollow Cathode Lamp (HCL) work?
When a voltage is applied, a current flows through the gas (usually argon or neon) inside the lamp, causing ionization. The gas ions collide with the metal cathode, vaporizing and exciting metal atoms, which emit light characteristic of the element.
Why is the light emitted by the HCL important for AA?
The light emitted by the HCL matches the specific wavelengths that the sample element absorbs, allowing for selective absorption measurement.
Why is the cathode made of the same element being analyzed
The cathode must be made of the element being analyzed because it emits the specific wavelengths of light that correspond to the absorption spectrum of that element.
What is the purpose of background correction in Atomic Absorption Spectroscopy (AA)?
The purpose of background correction is to compensate for non-specific absorption caused by molecular species, particulates, or scattering that interfere with the measurement of the element of interest.
Why is background correction necessary in AA?
It is necessary to ensure the accuracy of results by eliminating interferences from sources other than the analyte (e.g., molecular absorption, light scattering by particulates, or matrix effects).
What is a common method used for background correction in AA?
Deuterium Lamp Background Correction.
How does a deuterium lamp help with background correction?
The deuterium lamp emits continuous light across a broad range of wavelengths, allowing it to measure non-atomic absorption (background) over the same range as the atomic absorption signal.
What is the principle behind deuterium lamp background correction?
The atomic absorption signal is measured using the Hollow Cathode Lamp (HCL), while the background absorption (non-specific) is measured using the Deuterium Lamp. The instrument subtracts the background signal from the total absorption to isolate the atomic signal.
Why is the deuterium lamp useful for background correction?
The deuterium lamp produces a broad spectrum of UV light, which allows it to measure background absorption over a wide range of wavelengths, especially useful when molecular absorption overlaps with the atomic absorption signal.
How does the deuterium lamp help differentiate between atomic and non-atomic absorption?
The deuterium lamp does not excite atomic species, so any absorption it detects is purely due to non-atomic interferences, allowing the instrument to differentiate between atomic absorption (analyte) and background interference.
What is a key sensitivity advantage of the graphite furnace
It provides higher sensitivity compared to flame AA, with smaller sample volumes and longer analyte atomization time.
