The most harmful particles to humans are the ones we can’t see. That’s why scientists are turning to Particle Induced X-ray Emission (PIXE), an ion beam analysis (IBA) technique that measures the trace and minor elemental composition of a sample. In this post, we discuss how PIXE analysis works and how it’s helping environmental researchers tackle fine particle pollution.
Scientists around the world are taking an increased interest in Particle Induced X-Ray Emission (PIXE) to help solve the fine particle pollution problem. 50 times smaller than the diameter of a single strand of human hair, PM2.5 particles can make their way through the human nose, lungs and bloodstream – causing significant environmental and health risks for people especially in industrial and urban areas. To understand how to reduce the presence of these particles, researchers need to first understand where they come from. PIXE analysis makes this possible.
PIXE analysis is an analytical technique that uses high-energy particles to stimulate the characteristic X-ray emission from a sample, providing information about its elemental composition. PIXE analysis is a subset of Ion Beam Analysis (IBA), which is a broad set of techniques that use ion beams to characterize a material’s properties and composition.
Fighting fine particle pollution is just one application of the powerful technique. Labs are also using PIXE analysis for materials research, art fraud, and environmental monitoring due to the advantages of PIXE. These advantages include:
Here’s how it works in the context of fine particle pollution.
PIXE analysis starts with bombarding a sample with high-energy charged particles, which are typically protons (Proton Induced X-Ray Emission) or helium ions. The interaction between the charged particles and atoms in the target sample emits characteristic X-rays. These X-rays can then be detected and analyzed to determine the sample’s elemental composition.
#1. Prepare Sample
To investigate fine particle pollution, researchers first have to prepare samples for PIXE analysis.
One of the benefits of PIXE analysis is that there is no need for sample preparation beyond physically capturing the particles. To capture particles as small as PM2.5, researchers set up specialized filters in highly concentrated areas, like regions with tall buildings and manufacturing plants with a higher likelihood of having PM2.5 present.
High-volume air samplers can be installed at selected locations. These samplers draw a large volume of air through a filter over a specified period of time. To capture PM2.5, the right filter medium needs to be selected. Quartz filters are commonly used for this purpose. After the sampling period, the filters are removed from the air samplers and taken to the laboratory for PIXE analysis.
#2. Prepare the Accelerator for PIXE Technique
Conducting PIXE analysis on a sample requires an ion beam analysis accelerator system. While exact configurations will vary depending on the lab’s specific requirements, a complete system could include:
#3. Analyze Elements
The PIXE X-ray detectors capture and measure the energy and intensity of emitted X-rays. The X-ray spectra can be analyzed to quantify the concentration of elements in the sample. This analysis involves comparing X-ray peaks with known databases to determine the elements present and their respective concentrations.
For in-depth environmental monitoring, researchers examine X-ray peaks and correlate elements through a time series. Meaningful observations can be made after taking samples from various sites over longer periods of time.
Elements with strong correlations indicate a common source. Researchers can use specialized software to conduct positive matric factorization analysis, which identifies the sources of the particulate matter.
PIXE analysis is a fundamental technique for determining the elemental composition of a sample, including but not limited to air samples. PIXE involves bombarding a sample with high-energy ions, causing characteristic X-rays to be emitted. These X-rays are detected and analyzed to determine the elemental composition of the sample.
PIXE analysis has valuable applications in environmental studies, archaeology, material science, and other fields, contributing to our understanding of diverse samples and aiding in the development of policies for healthier living environments.
With over 50 years of accelerator experience, NEC provides industry-leading ion beam accelerator systems and related components to labs doing important work — including PIXE analysis. Tell us about your research needs today.