ICP-OES – Inductively Coupled Plasma Optical Emission Spectrometry for Trace and Elemental Analysis 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

Optical Emission Spectrometry

LSM Analytical Services large range of analytical techniques includes instrumentation for ICP-OES (inductively coupled plasma – optical emission spectroscopy).

How Do Optical Emission Spectrometers Work

Optical emission spectrometers determine analyte concentration via a quantitative measurement of the optical emission from excited atoms.

When a material is heated sufficiently it will emit visible light in a discrete spectrum, characteristic of the elements in the material. Each element has its unique atomic emission spectrum (both visible light and x-rays).

Different Modes of Operation for Optical Emission Spectrometers

There are 3 common methods to heat a sample to produce the optical emission:

• Arc/spark instruments; heat in a spark discharge
• ICP-Inductively Coupled Plasma; dissolve sample in acid and “burn” the solution in an argon plasma
• Glow discharge; sputter the surface with argon, and excite the sputtered atoms

Generating an Optical Emission by ICP

The ICP is simply the means by which the heat is generated. The ICP is essentially a high energy source (plasma) to raise the energy levels of electrons, and so induce an optical emission.

There are 3 stages in the life of a light beam; it is created it travels through space and it is destroyed. The ICP is the means used to create the light beam. It is the interaction of light with electrons, which is responsible for its creation and destruction.

In terms of the dual wave and particle like behaviour of light, it is simplest to envisage the particle like behaviour in terms of photons. As is the case with atomic absorption, electrons can be raised to higher energy levels by absorbing photons (destroy light), or move to lower energies by giving off a photon (create light).

Optical Emissions Specific to a Given Element

In atoms, the electrons are negatively charged and are held or bound by the positively charged protons in the nucleus of the atom. It is the specific binding energy of different elements, which determines their specific optical emissions.

Heat encourages light to be emitted over the whole energy region of visible light. The purpose of the ICP is to produce a spectrum of narrow lines, distributed in energy across the visible spectrum. Each line is characterised by the element atom, which emits the light.

Detection Limits for ICP-OES

The detection limits that ICP analysis can be performed to is determined by the equipment, and LSMs recent investment in state of the art technology allows detection limits in ppb parts per billion to be achieved.

Metals Analysed by ICP-OES

ICP is able to measure the following metals:

Source: LSM Analytical Services

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