Ever wondered what's hiding inside everyday objects? That's where elemental analysis comes in: a standardized method of material analysis. It uses robust techniques like X-ray fluorescence (XRF) to reveal the chemical makeup of any type of material. XRF is a favorite among researchers and experts in fields like engineering, forensics, and even archaeology, where it helps uncover secrets buried in ancient artifacts.
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How do Traditional X-ray fluorescence Instruments differ from Modern Hand-held Analyzers?
Imagine a tool that lets you see the invisible, revealing the building blocks of anything from a weathered coin to a cutting-edge computer chip. That's the power of X-ray fluorescence, a non-destructive technique that shines light on the hidden world of elements within materials.
Highly sensitive cryogenic detection systems made of Si(Li) and HPGe were unsuitable for portable instrumentation. The advancements in room temperature detector technology, such as CdTe PIN detection devices and Peltier-cooled silicon PIN diodes, resulted in spectrometers with comparable performance to cryogenic detectors. These spectrometers are now used in portable XRF analysis systems, resulting in significant improvements in instrument size and weight. The results indicate that Field Portable XRF is a suitable tool for non-destructive field analysis.
What are Modern Portable XRF Instruments
The research team that published Advances in Agronomy highlighted that although XRF instruments have performed elemental analysis for various industries for a long time, the introduction of portable X-ray fluorescence (PXRF) instruments has increased the cost and availability of this technology for a broader range of scientific applications.
Serving as a valuable tool for screening and assessing contaminated areas, PXRF analyzers enable the rapid and straightforward determination of trace element concentrations in situ.
PXRF spectrometry, despite being a smaller and portable version of the larger laboratory-based XRF instrument, operates on similar principles. The detectors used in PXRF systems vary, with gas-filled and scintillation detectors being traditionally common in XRF applications. However, portable XRF systems frequently utilize solid-state detectors, such as PIN diodes and SDD, to measure the energy of incoming photons through ionization produced in the detector.
How Have Portable XRF Instruments Developed Through the Years?
The first field-portable X-ray fluorescence (FPXRF) instrument, described by Bowie, Darnley, and Rhodes in 1965, utilized various radioisotopes and balancing crystals for XRF analysis in a battery-powered configuration. In 1968, two FPXRF instruments were developed—the Hilger PIF and another by Ekco Electronics Ltd—each determining one element.
During the mid-late 1990s, technological innovation led to the advancement of PXRF systems, making them more handheld, smaller, lighter, compact, and field-portable. This progress relied on the miniaturization of key components like X-ray tubes, electronics, and computer control systems.
In the last 20 –25 years, numerous manufacturers of PXRF equipment have introduced several new generations of equipment in quick succession, incorporating the latest technological advancements. While each instrument features proprietary software and hardware configurations, they all operate on the same general principle.
Light Elements are Not Detected Easily with Portable XRF
The energy of fluorescent X-rays directly corresponds to the atomic number of an element. Light elements, due to their low energy levels, face challenges escaping the sample and penetrating the air to reach the detector. Even if some of their fluorescent X-rays reach the detector, there must be a recognizable peak within the background noise for accurate concentration estimation, posing a challenge for light elements.
In portable XRF, measuring light elements is difficult because their fluorescence struggles to reach the instrument, making concentration estimation challenging. Consequently, detection limits for the lightest elements are higher (often 0.5-1%) as they require a higher concentration to produce a recognizable signal.
Recent improvements in portable XRF technology, particularly with silicon drift detectors (SDD), allow for applying more energy to boost the signal. SDDs enable the instrument to receive and measure more energy, improving detection limits and expanding the range of measurable lighter elements like Mg.
Limitations and Challenges
Portable XRF instruments have some major limitations, with the matrix effect being a significant one. In the matrix effect, the fluorescence rays being emitted are significantly affected by the physical and chemical properties of the specimen.
This effect can introduce errors, particularly for light elements, trace elements, or those influenced by factors like mineralogy, grain size, moisture, or coating. Correcting for the matrix effect involves using calibration methods such as fundamental parameters, empirical coefficients, or standard reference materials. However, these methods may not always be universally available, accurate, or suitable for diverse sample types or analyzers.
Portable XRF analyzers face a drawback in terms of lacking quality control procedures. This is because the performance of these analyzers is affected by physical and chemical phenomena. Hence, calibration tests must be performed at regular intervals to determine the accuracy of the device. However, the standardized calibration tests are not performed as per the schedule due to time constraints or carelessness.
An additional challenge in utilizing portable XRF analyzers lies in data management and interpretation. These analyzers can produce substantial data volumes rapidly, posing challenges in terms of storage, organization, and analysis. Further processing, including correction, normalization, or conversion, may be necessary to ensure comparability or compatibility with other data sources or methods. Hence, the utilization of portable XRF analyzers demands adept skills in data management and interpretation, along with the need for integration and collaboration with various disciplines and stakeholders.
In short, XRF Instruments have become handheld as the years have passed by and the technology has become more advanced.
More from AZoOptics: The Role of XRF in Ensuring Compliance with Metal Safety Standards
References and Further Reading
Horiba Scientific, (2023). What is X-ray Fluorescence (XRF) and how does XRF work?. [Online]
Available at: https://www.horiba.com/int/scientific/technologies/energy-dispersive-x-ray-fluorescence-ed-xrf/what-is-x-ray-fluorescence-xrf/
Jodi, M., (2019). What is Elemental Analysis Used For?. [Online]
Available at: https://www.rqmplus.com/blog/what-elemental-analysis-used-for
Portable Spectral Solutions, (2024). Why light elements are difficult to measure with portable XRF. [Online]
Available at: https://www.portaspecs.com/why-light-elements-are-difficult-to-measure-with-portable-xrf/
LinkedIn Community (2024). What are the advantages and disadvantages of using portable XRF analyzers for in-situ mineral analysis? [Online]
Available at: https://www.linkedin.com/advice/1/what-advantages-disadvantages-using-portable
ThermoFisher Scientific, (2020). What is XRF (X-ray Fluorescence) and How Does it Work?. [Online]
Available at: https://www.thermofisher.com/blog/ask-a-scientist/what-is-xrf-x-ray-fluorescence-and-how-does-it-work/
Weindorf C et. al. (2014). Advances in portable X-ray fluorescence (PXRF) for environmental, pedological, and agronomic applications. Advances in agronomy, 128, 1-45. Available at: https://doi.org/10.1016/B978-0-12-802139-2.00001-9
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