New Method Developed for Fast and Accurate Determination of Zinc and Iron in Vegetables

Iron and zinc are important micronutrients essential for human health, and their contents in foodstuffs are crucial for assessing nutritional value. A new method for simultaneous determination of zinc and iron in vegetables and plant material has been developed by researchers at Masaryk University in Brno, Czechia. The study was published in the journal Spectrochimica Acta Part B: Atomic Spectroscopy (1).

Food background with assortment of fresh organic vegetables | Image Credit: © Alexander Raths - stock.adobe.com

The method utilizes high-resolution continuum source graphite-furnace atomic absorption spectrometry (HR-CS GF-AAS) to measure adjacent secondary lines of zinc and iron simultaneously in a single firing, which makes the analysis fast and sensitive. The sensitivity of the method corresponds to common concentrations of the elements in foodstuffs, and the accuracy was verified using reference materials and comparison with an independent technique. The analysis can be completed in under 2 minutes, which makes the method suitable for routine laboratory settings.

HR-CS GF-AAS is a technique used for the determination of trace elements in various samples. It uses a high-resolution continuum source (HR-CS) spectrometer that provides broad-spectrum light for the excitation of analyte atoms in the graphite furnace. This technique allows for the simultaneous determination of multiple elements at once, and its sensitivity corresponds to common concentrations of elements in foodstuffs. HR-CS GF-AAS is a fast and routine-ready method that offers improved analytical usability.

The research team tested the new method on a large set of vegetable samples obtained from both markets and local gardeners. The results indicate that homegrown vegetables have higher contents of zinc and iron compared to store-bought ones. This finding highlights the potential benefits of growing vegetables at home, especially for individuals with micronutrient deficiencies.

Traditionally, determination of zinc and iron in foodstuffs is done using atomic spectrometric-based methods such as flame or graphite furnace atomic absorption spectrometry (F-AAS and GF-AAS), inductively coupled plasma with optical emission (ICP–OES) or mass spectrometry (ICP–MS). However, GF-AAS has not been the first-choice method for determining iron and zinc due to their low detection limits in the sub-μg/L^-1 range. This limits the analysis as these elements are critical with regard to contamination from solvents, containers, and laboratory air. Using alternate wavelength is a common approach to decrease this oversensitivity, but Zn has only one alternate spectral line of very low sensitivity.

The introduction of HR-CS spectrometers has made GF-AAS much more suitable for measuring high concentrations, and secondary lines have improved analytical usability. The new method developed by the researchers provides a fast and accurate way to determine zinc and iron in vegetables and plant material, which will aid in assessing nutritional value and identifying potential deficiencies.

Reference

(1) Zvěřina, O.; Vychytilová, M.; Riger, J.; Goessler, W. Fast and simultaneous determination of zinc and iron using HR-CS GF-AAS in vegetables and plant material. Spectrochim. Acta. Part B At. Spectrosc. 2023, 201,106616. DOI: https://doi.org/10.1016/j.sab.2023.106616