Elemental analysis is performed to determine which elements the sample contains and the quantities they are present in. It is an essential tool for quality assurance and troubleshooting to help ensure that the elemental composition of a substance, material, or product meets legal requirements, industry standards, and customer expectations.
Types of elemental analysis
Elemental analyses can be divided into different categories depending on the abundance of the analyzed elements in the material. Major element analysis is used to determine the bulk composition of the sample, while the purpose of minor or trace element analysis is to identify small impurities from a substance with a known bulk composition.
Another distinction can be made between qualitative and quantitative elemental analysis. Qualitative analysis provides information on which elements are present, while quantitative analysis also yields their amounts. Typically, elemental analysis provides both quantitative and qualitative information, regardless of the used analysis method.
Legal testing requirements and other quality standards
The goal of elemental analysis can be to ensure that a substance or material complies with legal restrictions on hazardous elements, such as heavy metals. For example, the EU food contaminant regulation 2023/915 imposes maximum limits for lead, mercury, arsenic, and cadmium in several types of food. Similarly, the REACH regulation limits the presence of heavy metals in consumer products. In addition to these examples, elemental quantities are assessed carefully in the environmental and fuel industries.
More often than not, the internal quality standards of the manufacturer or the customer are stricter than legal requirements.
Choosing an elemental analysis method
Various techniques can be used for elemental analysis. The choice of the most appropriate method depends on sample characteristics, the elements of interest, and the required sensitivity. Asking the following questions is a good way to get started:
What is known about the sample? Is it organic or inorganic? What are its major components? Unknown substances can also be analyzed, but the results can be less reliable due to possible matrix interferences.
What needs to be determined – bulk composition, or chemical purity? A highly sensitive method is needed to detect contaminants in trace quantities.
Which elements need to be analyzed? Different analysis methods have their own element ranges, affecting the available methods. Typically, light element (H to Be) analysis has a narrower scope of analysis methods.
Does the sample need to be dissolved, or is a surface method needed?
What is the purpose of the measurement? Is there a specific regulation that should be used as a reference? Is there a need for a standard analysis method or an accredited method?
Method comparison
Table 1 summarizes some common elemental analysis techniques, along with their elemental range and sensitivity. More information on each method is provided further on.
Table 1: Comparison of popular elemental analysis techniques
Method | Detectable elements | Sensitivity* |
ICP-OES/MS/SFMS | Li to U | ppm to ppt |
AAS | Mainly metallic elements, up to 70 elements | ppm |
CHNOS | C, H, N, O, S | 0.05–0.1 wt% |
XRF | Be to U | 10 ppm–1 at% |
SEM-EDX | All except H, He, and Li | 0.1–1 at% |
ERDA | H to U | 0.1–0.5 at.% |
RBS | Be to U | 0.1 at% |
* These are rough estimations, as sensitivity depends on the equipment and the analyzed sample.
ICP methods – versatile and sensitive
ICP-based techniques (ICP-OES, ICP-MS, and ICP-SFMS) provide a good starting point for determining elemental concentrations, if there is no specific reason to choose another method. In most cases, ICP suits both organic and inorganic sample types, and with it, most elements can be detected at the ppm level. Typically, ICP methods take into account the composition of the material as a whole, as the measurement is performed on a homogenized sample dissolved with a suitable acid. Due to the low detection limit, ICP excels in trace element analysis.
In terms of limitations, ICP sometimes requires strong solvents like aqua regia or hydrofluoric acid to be used, which can pose a work safety risk. Conventional ICP methods are not suited for samples that cannot be dissolved. Sample preparation techniques like vapor phase decomposition or laser ablation can, however, be used to enable ICP-MS analysis of trace metal impurities on thin films and wafers.
Standard ICP analyses are generally quite affordable, as measurements are performed routinely and the equipment is widely available. Complex sample types require more extensive preparation and can be more expensive to analyze.
CHNOS, AAS, and XRF – routine techniques for basic analysis
CHNOS analysis is used to determine the amounts of carbon, hydrogen, nitrogen, oxygen, and sulfur in organic sample materials. The technique works well when determining bulk composition but is not sensitive enough for trace element analysis. An advantage when compared with ICP methods is the ability to detect hydrogen.
AAS is a relatively straightforward technique for detecting certain metals in low concentrations, but unlike ICP methods, it can only detect one element at a time, and multielement analysis is done sequentially, increasing analysis run time and costs. Although the analysis technique relies on a similar detection phenomenon to ICP-OES, ICP methods have largely replaced AAS due to the above-mentioned reasons.
XRF is a common method for detecting elements from fluorine to uranium in samples including minerals, metals, ceramics, and liquids. Solid samples do not need to be dissolved, although they may need to be cut, polished, or prepared as a homogenous powder and processed into tablet form.
SEM-EDX, ERDA, and RBS – surface analysis and depth profiling
Techniques like SEM-EDX, ERDA, and RBS are most commonly used to analyze microchips, thin films, semiconductors, and nanomaterials. The elemental composition can be determined from the surface of such samples, in addition to which the material can be gradually etched away to obtain information about elemental concentrations as a function of depth.
Out of these methods, ERDA is the only one capable of detecting hydrogen and helium, making it the definitive surface analysis technique for quantifying light elements. The main advantage of SEM-EDX is simultaneous imaging of the sample, which makes it possible to visualize elemental concentrations in different locations. RBS’s strength is the ability to provide quantitative results on multiple elements without reference standards.
Measurlabs offers elemental composition analyses using all the techniques mentioned above – and more. Do not hesitate to contact us through the form below to request a quote for your product or material.