Methods for analysis of the distribution and speciation of iron and zinc in the cereal grain

Research output: Book/ReportPh.D. thesisResearch

Deficiency of iron (Fe), zinc (Zn) and other mineral micronutrients is a worldwide problem affecting more than 50% of the world’s population, especially in human populations depending on a cereal diet. Mineral micronutrients are not distributed evenly in the cereal grain and a large fraction is lost during the milling processes used to remove the outer layers of the grain. Furthermore, the bioavailability of the Fe and Zn remaining in the grain is low, thus underlining the need for improved understanding of the factors controlling their distribution and speciation.
The distribution of mineral micronutrients in cereal grain primarily depends on two main components; phytic acid and proteins. Most of the phosphorus (P) found in the grain is bound in phytic acid and most sulphur (S) is incorporated into the amino acids cysteine and methionine that are part of different proteins.
Co-localization and identification of P and S with mineral micronutrients can therefore be a circumstantial evidence for their chemical speciation. The focus of this PhD has therefore been on the analysis of mineral micronutrients as well as S and P.
In this PhD, four methods for elemental analysis of the cereal grain have been developed based on Inductively Coupled Plasma Mass Spectrometry (ICP-MS).
A multi-elemental method including Zn, Fe, S and P was developed in which oxygen was used as a reaction gas in the ICP-MS system to enhance the sensitivity of S. This enabled simultaneous detection of Fe, Zn, S, P and some other mineral micronutrients in extracts of a cereal grain, especially because S was measured with an increased sensitivity without decreasing that of the other elements. This novel analytical method paved the road for multi-elemental speciation and elemental imaging studies of the cereal grain.
In addition, a novel high-throughput micro digestion method was developed, enabling the analysis of total element concentrations in small tissue fractions, such as the embryo of cereal grains. The method is based on small closed bombs that are microwaved and was validated for sample amounts between 1-20 mg using certified reference materials. This enabled high-throughput analysis of different grain tissue fractions and the variability in between them.. Moreover two methods for quantitative hyphenated ICP-MS analysis were developed. One enabled quantification of species in a chromatographic separation and the other enabled quantitative bioimaging of elements using Laser Ablation (LA). Both methods were developed and validated for grain analysis.
Taken together, the methods developed have constituted the main analytical cores in 17 peer reviewed papers of which 8 form the the basis for this PhD. The articles have contributed to the growing understanding of how the nutritional value of cereals can be increased and provided researchers with analytical methods that will help to resolve the complexity associated with biofortified cereal products.
Original languageEnglish
PublisherDepartment of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen
Number of pages183
Publication statusPublished - 2012

ID: 44023164