Xrf Analysis

Physical Process

Interaction of the primary x-rays with the atoms in the sample causes the ejection of electrons from the inner shells, creating an unstable state. As electrons from the outer shells drop down to fill these vacancies, they release energy in the form of fluorescent x-rays. In xrf analysis, the energy of these secondary x-rays is characteristic of the specific element that produced them, while the intensity of the signal is proportional to the concentration of that element in the sample.

The spectrometer captures these x-rays and uses a detector to measure their energy and count the number of photons at every energy level. This data is then processed by a computer to create a spectrum that displays peaks for every element present in the sample. This process is very fast, with a complete elemental analysis often taking less than a minute.

The non-destructive nature of the test is a major advantage, as it allows the same sample to be used for other tests or returned to the production line after the analysis is complete.

Quality Control

Verification of the elemental composition of raw materials and finished parts is the primary application of this technology on the factory floor. When a shipment of metal billets or plastic pellets arrives, a portable xrf analyzer can be used to quickly confirm that the material matches the grade specified in the purchase order. In the context of xrf analysis, this is known as positive material identification and is a critical step in preventing the use of the wrong material in a manufacturing process.

For example, a factory can quickly distinguish between different grades of stainless steel that look identical but have very different corrosion resistance properties. This testing is also used during the assembly process to ensure that the correct components have been used and that no mistakes were made during the welding or joining of different parts. The results of these tests are recorded in a digital database, providing a permanent record of the material’s composition that can be used for traceability and audit purposes.

This real-time feedback allows for the immediate correction of any problems, reducing the risk of making a large number of defective parts.

Compliance Testing

Screening for hazardous substances is a mandatory requirement for many products under the jurisdiction of the RoHS directive and similar regulations in China. Manufacturers use xrf analysis to ensure that their products do not contain concentrations of restricted heavy metals that exceed the legal limits. This is particularly important for electronics and toys, where the presence of lead or cadmium can pose a serious health risk to consumers.

The portable nature of many xrf units allows for testing to be performed at various points in the supply chain, from the raw material supplier to the final assembly plant. During a regulatory audit, the factory can use their xrf records to prove that they have a robust screening program in place and that their products are in full compliance with the law. While xrf is an excellent screening tool, any results that are close to the legal limit are usually verified using more sensitive laboratory methods like inductively coupled plasma mass spectrometry.

The use of this analysis helps to protect the manufacturer from the legal and financial risks associated with non-compliant products and ensures that the items they produce are safe for use by the public. This final verification of the elemental content is an essential part of the modern quality and safety management system.