Energy dispersive X-ray fluorescence (EDXRF) spectroscopy is a rapid and non-destructive elemental analysis technique. It helps food labs optimize production processes and minimize downtime. EDXRF is used to measure nutrients and fortificants, screen for contaminants and incidental adulterants, and identify foreign body contaminants found during production or packaging.
EDXRF performs measurements on all kinds of samples including liquids, solids, or loose powders. It combines high accuracy and precision with minimal sample preparation. It provides simultaneous analysis of elements from carbon to americium and for elemental concentrations from ultra-trace levels up to 100 percent, depending on the specific instrument configuration.
EDXRF is a powerful, green alternative to traditional atomic spectroscopy methods. Sample preparation is rapid and non-destructive with no hazardous waste disposal regulations to be concerned with. Additionally, EDXRF has comparatively low operation or maintenance requirements and costs.
Options of this type of spectroscopy includes the following.
- Benchtop EDXRF is the food lab method of choice for dedicated applications in quality and process control with its ease of use and compact size. It delivers speed and analytical flexibility for a multitude of research and monitoring tasks.
- Micro-XRF is the food lab method of choice for high-speed, two-dimensional elemental analysis of non-homogeneous or irregularly shaped samples as well as small samples or inclusions.
- Total reflection XRF (TXRF) spectrometry is the food lab method of choice for rapid ultra-trace elemental analysis, low parts-per-million (ppm) and parts-per-billion (ppb) of multiple sample types.
- Handheld XRF (HHXRF) is the food lab method of choice when an analyzer needs to be brought to the sample for immediate analysis rather than transporting the sample to the lab.
Analysis of Elemental Nutrients and Fortificants
Benchtop EDXRF analyzers quickly measure elemental nutrient and fortificant content in food products at any stage of production, from incoming raw materials to end products. This includes elemental additives such as sodium and potassium or fortificants such as iron and calcium in milk products. EDXRF also measures elemental nutrient content such as selenium and molybdenum in dietary supplements or magnesium and iron in animal feed.
Micro-XRF goes one step further by providing visual images of the nutrient or fortificant distribution on or within the food product. A slice of produce is measured to determine elemental nutrient rich locations, such as in bananas and apples. Micro-XRF also provides elemental fortification distribution maps of crackers, chips, or cereal to help optimize food processing. Mapping images for the distribution of phosphorus, sulfur, and iron on cereal as well as salt distribution on snacks help determine effective fortification process steps.
Analysis of Incidental Adulterants and Contaminants
EDXRF is ideal for routine analysis of incidental adulterants and contaminants in foods at any stage of the product. These efficient analyzers quickly identify and quantify incidental adulterants such as lead or chromium from colorants, mercury or copper from fungicides, lead from water, or arsenic and bromine from pesticides. Minimal sample preparation is required to achieve high precision and accuracy of results.
TXRF is best suited for ultra-trace elemental analysis. While it is a powerful tool for food fraud prevention in globalized supply chains, it’s particularly relevant for food safety as outlined by the Food & Agriculture Organization/World Health Organization (FAO/WHO) standards, stating it can directly analyze low levels of arsenic in rice or lead in tea drinks. Its versatility for the analysis of multiple sample types as well as minimal sample preparation requirements for even complex samples makes it much faster than inductively coupled plasma emission spectroscopy, which requires fully dissolved liquid samples for analysis.
Identification of Foreign Body Contaminants Found
Contaminants are the last thing anyone wants in their final products, but with virtually non-stop use of production line equipment such as food augers, roller mills, air locks and drying conveyors, they happen. When contaminants are found, the use of handheld XRF can help food labs quickly identify the foreign body and find its source to fix the problem before any more product is contaminated.
HHXRFs configured with internal libraries of standard alloy and metal grades and compositions identify the contaminants. However, to determine the source of foreign bodies, an XRF audit of all equipment on the production floor is performed first. Simple 30 second test results of all metal surfaces which come in contact with food, or have a potential for breaking, provide a production floor matching catalog. This contains the metal or alloy grade and elemental composition of each piece of equipment, component, piping, or part tested. When more than one source of an identified contaminant is possible from the matching catalog, spectral fingerprint matching is used to take a closer look. Advanced qualitative PC software for HHXRF is used to match the spectral fingerprint of the contaminant to that of its source.
How EDXRF Measures Elements Quickly
Atomic spectroscopy is the most commonly recommended technique for evaluating the elemental composition of samples. It analyzes the interaction between light (energy) and matter (samples). EDXRF is a non-destructive, versatile, and fast spectroscopy technique with minimal sample preparation requirements; and, it can be designed as laboratory or portable analyzer.
In a way, EDXRF is like a high-powered flashlight that sees beyond what humans can. When the light source is turned on to illuminate a sample, it “sees” the energy of any elements present. It also “senses” how much of those elements are present by their energy’s magnitude. For example, when EDXRF illuminates a sterling silver coin, it detects silver at 22.163 keV and copper at 8.046 keV; and, it determines the coin’s composition to be 92.5 percent silver and 7.5 percent copper.
The process of EDXRF elemental analysis of a sample is as follows:
- Energy from an EDXRF source aimed at a sample can eject the sample’s atoms’ inner orbital electrons;
- Outer electrons move into those voids to regain stability;
- While moving in, the outer electrons generate energy characteristic of elements in the sample;
- Resultant energy is detected and processed to determine which elements are present in the sample;
- EDXRF spectrometry results are represented as graphs or spectra showing intensity as a function of energy; and
- The intensity (number of photons) measured at a given element’s energy determines its relative abundance or concentration.
Benchtop EDXRF. These analyzers have the widest range of elemental detection, from light elements such as carbon to heavy elements such as americium with short analysis times, high precision, and excellent detection limits. They are the most versatile in
terms of setting up user specific calibrations for virtually any analysis scenario. And, they typically have the most advanced and comprehensive qualitative and quantitative data analysis software capabilities available.
Benchtop EDXRF analyzers are closed beam systems that can be configured with air, helium, nitrogen, or vacuum atmospheres. Closely coupled thin window X-ray tubes with power up to 50 watts and 50 kV excitation voltage for direct excitation, automatic filter changer selection and high energy resolution silicon drift detectors (SDD) enable the wide elemental analysis and low detection limit range. They are self-contained with a touch screen for user-friendly routine analysis and a variety of connectivity ports. Options typically include internal cameras, automatic sample changers and spinners.
Micro-XRF. This elemental analysis technique with a spatial resolution significantly smaller than conventional EDXRF enables micron size sample analysis. It is especially helpful for analyzing small particle wear debris found during production or particle inclusions in plastic film found during packaging. When micro-XRF is combined with sophisticated elemental mapping software, it is ideal for studying the distribution of nutrients in foods, such as produce, and of fortificants on foods, such as cereal and snacks.
Micro-EDXRF is configured as a closed-beam benchtop two-dimensional micro-XRF spectrometer, typically with a 30W powered rhodium X-ray tube, SDD detector, programmable X-Y-Z stage, fish eye camera, optical video microscopes, polycapillary X-ray optics for spot sizes of 25 micrometers, and software designed for collecting large elemental data sets and mapping distribution via “stitching.”
TXRF. These analyzers provide ultra-trace (PPB and PPM) quantitative and semi-quantitative multi-elemental microanalysis. This capability is especially critical for ultra-low, but dangerous levels of heavy metals like arsenic and lead. TXRF spectrometers provide fast quantitative and semi-quantitative multi-element analysis of liquids, suspensions, and contaminants. TXRF is optimally suited for trace elemental analysis reaching ppb and ppm detection limit ranges.
TXRF analyzers are configured with a 50W, 50 kV X-ray tube, multilayer monochromator optics and an SDD detector to provide fast and accurate measurement of ultra-trace elements as low as 0.1 ppb in liquids. They have a variety of sample chamber tray configurations; and, in contrast to most analytical methods, sample amounts in nanograms to micrograms are sufficient.
HHXRF. When you can’t take samples to the analyzer, you can bring a portable XRF to them. HHXRF analyzers are the most agile XRF analyzers for the simultaneous measurement of elements anywhere they’re needed. Although they are primarily used for in-situ
measurements, such as alloy or metal identification of in-use equipment or incoming materials, they can also be set up in benchtop stands for use with prepared or small samples. They are ideal when immediate results are needed on the production floor.
HHXRF is an “open-beam” technology, typically with a 2-4W powered X-ray tube, silicon PiN or SDD detector, internal camera, variable spot sizes up to 8 mm, application-specific filters, and software capable of qualitative and quantitative analysis. Some HHXRF analyzers provide the ability to use customized filters and even vacuum or helium flush for light element analysis.
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