Potential of multivariate analyses of X-ray fluorescence spectra for characterisation of the microchemical composition of plant materials

A. Brangule¹³*, M. Bērtiņš², A. Vīksna² and D. Bandere¹

¹Riga Stradins University, Department of Pharmaceutical Chemistry, Dzirciema 16,
LV-1007 Riga, Latvia
²University of Latvia, Faculty of Chemistry, Jelgavas 1, LV-1004 Riga, Latvia
³Baltic Biomaterials Centre of Excellence, Headquarters at Riga Technical University, Kalku street 1, LV-1658 Riga, Latvia
*Correspondence: agnese.brangule@rsu.lv

Abstract:

This work describes a method for the rapid element analysis of plant material using ED-XRF in conjunction with chemometrics. An effective analysis method is developed by measuring certified reference materials (CRM) of plant materials (algae, cabbage, lichen) covering major chemical elements with ED-XRF, to overcome the matrix effect. All samples have been measured additionally by ICP-MS. The ICP-MS analysis was used for missing information on the concentration of some elements in certificated standards. In addition, ICP-MS with CRM has been used to determine sample related element sensitivity for microelements for ED-XRF analyses.

The ED-XRF spectral patterns were used for multivariate principal component analyses by SIMCA strategy instead of each element concentration calculation. The model allows quickly analyse samples for similarity and differentiate them based on a little difference in spectral pattern, which corresponds to a minor difference in element concentration pattern. Samples with specific chemical composition could be easily spotted for in-depth analysis.

The proposed strategy for plant material sample chemical composition screening allows the quick method to improve laboratory work efficiency, reduce unnecessary analysis and rapid method for control reliability of results of more complex chemical methods, such as ICP-MS.

Key words:

chemometrics, ED-XRF, ICP-MS, Multivariate analysis, plants, screening analysis, SIMCA

Impact of different fertilisers on elemental content in young hybrid aspen stem wood

M. Bertins¹*, A. Bardule², L. Busa¹, A. Viksna¹, D. Lazdina² and L. Ansone-Bertina³

¹University of Latvia, Faculty of Chemistry, Department of Analytical Chemistry, 1 Jelgavas street, LV-1004 Riga, Latvia
²Latvian State Forest Research Institute “Silava”, 111 Rigas street, LV-2169 Salaspils, Latvia
³University of Latvia, Faculty of Geography and Earth Science, Department of Environmental Science, 19 Raina Blvd, LV-1586 Riga, Latvia
*Correspondence: maris.bertins@lu.lv

Abstract:

The biomass production using fast-growing tree species such as hybrid aspen (Populus tremuloides Michx. x Populus tremula L.) has been recognized as an environmentally friendly and cost-effective approach. Growing these species can reduce the negative impact of earlier land mismanagement and at the same time provide additional biomass growth. The application of fertilisers may introduce not only the necessary macro elements (N, P, K) but also significant amounts of toxic heavy metals. Therefore, the knowledge about elemental flows from fertilised soil to the different parts of hybrid aspen trees is essential and especially meaningful for the evaluation of element content in specific environmental ecosystems. The impact of different fertilisers (sewage sludge, digestate and wood ash) on the concentrations of micro- and macro elements in the wood of six-year-old hybrid aspen stands grown on former agricultural land was studied. The determination of element concentrations in different tree rings of hybrid aspen trees was accomplished by inductively coupled plasma mass spectrometry (ICP–MS). Isotope ratio mass spectrometry (IRMS) was used to determine the nitrogen and carbon content and isotope ratios in different parts of hybrid aspen trees. Stem disc samples from hybrid aspen trees were obtained from agricultural land in the central part of Latvia. Samples were taken from six-year-old hybrid aspen trees that at the moment of planting were fertilised with sewage sludge, a residue of biogas production (digestate) and wood ash. The obtained results indicated that the chemical element accumulation in hybrid aspen was affected by the applied fertiliser type. In this study, the use of wood ash, as well as digestate, affected the elemental content in hybrid aspen to a greater extent than the use of sewage sludge, relative to unfertilised (control) subplot. The analysed elements varied in the analysed stem plane (across the tree rings). The most significant changes between the rings were observed for the content of K and Ca.