Atomic Absorption Spectroscopy (AAS) – Determination of Chemical Composition of Metals and Ceramics by LSM Analytical Services

Background

LSM Analytical Services offer a large and diverse range of modern analytical testing facilities that cater for a vast range of industry sectors. LSM’s success has been achieved by building on a strong reputation for low cost, fast accurate turnaround. The laboratory activities are backed up by accreditation to the ISO 17025 (UKAS) and 9001:2000 laboratory and quality management standards. LSM is able to offer complete analytical solutions from its internationally recognised team of technical experts, with in depth knowledge, allowing its customers to benefit from impartial guidance.

LSM’s range of analytical services includes:

• X-Ray Fluorescence Spectrometry (XRF)
• X-Ray Diffraction (XRD)
• ICP Optical Emission Spectrometry (ICP-OES)
• Atomic Absorption Spectrometry (AAS)
• Carbon, Sulphur, Nitrogen, Oxygen Analysers
• Boron analysis by the Neutron Transmission method
• Colorimetric and Volumetric Analysis
• Particle Size Analysis

Atomic Absorption Spectroscopy

LSM Analytical Services has analysis methods for trace analysis of metals and oxides by atomic absorption spectroscopy.

It is a technique used to determine the concentration of a particular metal in a sample. It usually involves the use of a flame to atomise the sample, but other methods such as a graphite furnace are also used.

Converting a Liquid Sample into an Atomic Gas

There are 3 steps involved in turning a liquid sample into an atomic gas

1. Evaporation of the liquid to leave a dry sample
2. Vaporising the solid sample to a gas, and
3. Atomisation to break down the compounds present into free atoms.

Flame atomic absorption spectrometry is a fast and easy technique with an extremely high sensitivity, but specialist knowledge is required in its use as issues arise from chemical and spectral interferences.

How Atomic Absorption Spectrometers Work

Atomic absorption spectrometers use the absorption of light to measure the concentration of gas phase atoms. The light that is focused into the flame is produced by a hollow cathode lamp, inside which is the sample and an anode. A high voltage is passed between the cathode and anode and the metal atoms are excited into producing light with a certain emission spectrum.

An atom consists of a core containing neutrons and protons. It also has a surrounding number of electrons, which are bound to the core at different energy levels. When an electron makes a transition from a particular energy level of an atom to a lower energy level, a photon of energy is released, which is equivalent in energy to the reduced level for the electron. The photon forms an atomic spectral line.

The frequency (v) at which the spectral line occurs is related to the energy (E) by Planck’s law; E = hv, where h is Planck’s constant. The atomic radiation produced can be characterised by both emission and an absorption coefficients. As the quantity of energy put into the flame is known and the quantity emitted can be detected, it is possible to calculate the concentration of the element present.

Metals that can be Detected by Atomic Absorption Spectroscopy

This method can be used to detect metals such as:

Source: LSM Analytical Services

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