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It’s safe to say, that because there are so many different elemental analysis techniques that can be used in many branches of science, knowing which one is best for an intended application can tricky. There are also different classifications of elemental analysis, which measure the elements present in a sample or the number of elements/concentration of elements in a sample. These are known as qualitative and quantitative analyses, respectively. There are also many techniques that can perform both. In this article, we’re going to look at the most common and versatile techniques that can be applied to many different industries and for many applications within these industries.
Even though there are many techniques that can be used to perform an elemental analysis, not all are created equal. In general, for the many techniques that are specific to a single industry, there are also many techniques that can be used for both that industry as well as others—so these have become techniques that are widely used in today’s elemental analyses, whilst more traditional methods have been phased out. As it stands, there are a few different techniques that are highly versatile and can provide both quantitative and qualitative analyses. These are atomic absorption spectroscopy (AAS), atomic emission spectroscopy (AES), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and inductively coupled plasma mass spectrometry (ICP-MS).
Atomic Absorption Spectroscopy (AAS)
AAS is a technique that many people use if they need to measure more than 5 elements within a sample in the parts per million (ppm) range. In AAS the sample is solubilized (if it is not already a liquid) and is heated to a high temperature. The high temperature causes the sample to be atomized and it is then subject to various wavelengths of electromagnetic radiation. The sample then absorbs some of these wavelengths and a detector captures the wavelengths which are not absorbed by the sample. This enables the instrument to determine which wavelengths were absorbed, and because each element has specific absorption characteristics, it enables the elements to be identified. The amount of each element is determined by how much of each wavelength is absorbed.
AAS is heavily used in the petrochemical industry in petroleum refining applications and in nutritional labeling within the food industry. It is also a widely used technique for measuring air samples in environmental monitoring applications, for measuring the quality of products in the chemical industry, and for analyzing the purity of chemicals in the semiconductor industry. It is also used to measure the safety of foodstuffs, in exploration applications in the geochemical and mining industries, for analyzing biological fluids in biomonitoring processes, and for analyzing nanomaterials.
Atomic Emission Spectroscopy (AES) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES)
AES and ICP-AES are both widely used techniques which rely on similar principles and are usually used to analyze more than five elements in the parts per billion range (ppb). Both techniques are similar to AAS, in that the samples are bombarded with electromagnetic radiation. However, AES and ICP-AES measure the wavelengths emitted from the sample after the sample has been excited by the incident radiation. Each element has characteristic wavelengths that they emit once they have been excited, and this enables the types of elements in a sample to be deduced. The intensity of the characteristic wavelengths is what determines the concentration of each element in the sample. Where AES and ICP-AES differ is in the pre-atomization of the sample before it is analyzed, where AES uses a flame to atomize the sample and ICP-AES atomizes the sample by converting it into a plasma.
These techniques are heavily used to analyze soil and water samples in environmental monitoring applications, in the food industry for nutritional labeling (and in food safety applications but to a lesser degree), as a quality control method in the pharmaceutical and chemical industries, in petroleum refining, lubricant analysis, and oil analysis applications within the petrochemical industry, in exploration and research applications in the geochemical and mining industries, for analyzing soils in the agricultural industry, and for analyzing biofuels and solar panels in the renewable energy industry. They are also widely used in the nuclear industry for analyzing low-level waste and process water.
Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
ICP-MS is another method used across many industries because it can analyze many elements within a sample at the parts per trillion (ppt) level. ICP-MS uses the same atomization principles as ICP-AES and converts the sample into a plasma before being analyzed. The plasma then enters the MS compartment of the instrument (after an intermediate region) and the elements are separated by their mass-to-charge ratios. This enables each element to be identified individually, and the concentration of each element can also be backed out using calibrated reference samples.
ICP-MS is a technique that is heavily used in the pharmaceutical industry for drug development applications and for quantifying the concentration of metals in a sample, for analyzing soil, water and air samples in environmental monitoring applications, in petroleum refining applications in the petrochemical industry, in exploration and research applications in the geochemical and mining industries, for analyzing biological fluids in biomonitoring applications, for analyzing biofuels, and for analyzing wafers and the purity of chemicals in the semiconductor industry.
It is also a technique that is widely used to measure the levels of titanium within sunscreens, as a method for performing a trace element analysis, for measuring the level of metals in food safety applications, as a quality control method in the chemical industry, for analyzing low-level waste and process water in the nuclear industry, for analyzing solar panels, and for analyzing nanomaterials.
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