Review of Portable X-ray Fluorescence in Analysis Applications for Solid and Liquid Food Samples

A new study in the journal TrAC, Trends in Analytical Chemistry offers a review of portable X-ray fluorescence (pXRF) spectrometers in the context of their applications for fast, precise, and facile analysis of food products (1). Because pXRF spectrometry has the additional advantages of being sustainable, low-cost, non-destructive, and adaptable to either solid or liquid samples, the intent of the research was to convey to food toxicologists that pXRF’s reputation in food analysis is valid, and that that analysis can be further improved with increased use of pXRF.

Ripe green pears and red apples in a wooden box with grunge texture, top view. Autumn harvest of pears | Image Credit: © isavira - stock.adobe.com

Written by toxicologists Adrian Frydrych and Kamil Jurowski, both affiliated with the Laboratory of Innovative Toxicological Research and Analyses in the Institute of Medical Studies, Medical College at Rzeszów College in Rzeszów, Poland, this review compared 11 different pXRF spectrometers manufactured by a handful of research labs and manufacturers. The food items that were analyzed included apples, malted barley, candy, chocolate liqueur, cocoa powder, flour, lettuce, pears, rice, tomatoes, and unspecified dietary supplements (1).

According to the authors, while X-ray fluorescence protects the sample matrix of an experiment and reduces the production of waste, it can also categorize food products according to their geographical region, or fingerprint, and ecological status (1). TXRF, or total reflection XRF, is a similar method and is ideal for food analysis because it allows for simultaneous detection of elements in a wide range of concentrations. But portable XRF, as its name would suggest, is fully mobile and is cost-effective, overall being more favorable than inductively coupled plasma (ICP)-based equipment, which the researchers said has historically been more commonly used in food analysis.

By using a handheld XRF instrument, the researchers said, not only is the fingerprinting of elements in food able to be performed—something the study said came into vogue only as recently as 2009—but both trace and toxic elements are able to be screened in multiple matrices. In the case of the dietary supplements previously mentioned, this included in some instances traces of silver (1). Additionally, the study raised concerns about the presence of lead and other heavy metals in edible plants, which enter those organisms through soil. Previous studies were also not able, the researchers said, to effectively judge either limits of detection or quantification for potentially hazardous elements for human consumption.

In conclusion, the authors reported “considerable potential” for the use of pXRF in analyzing food samples with precision (1). They pointed to rapid analysis time as being especially important when it comes to perishable food products, also mentioning that pXRF eliminates a need for sample pretreatment. But they also admitted that the knowledge base for this technique and particular application remains limited and suggested that further research be focused on developing standardized protocols for pXRF measurements to be used by the food industry at large.

Reference

(1) Frydrych, A.; Jurowski, K. Portable X-ray Fluorescence (pXRF) as a Powerful and Trending Analytical Tool for in situ Food Samples Analysis: A Comprehensive Review of Application – State of the Art. TrAC, Trends Anal. Chem. 2023, 166, 117165. DOI: 10.1016/j.trac.2023.117165