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

Use of principal component analysis to evaluate thermal properties and combustibility of coffee-pine wood briquettes

C.L. Mendoza Martinez¹²³*, E. Sermyagina¹, M. Silva de Jesus³ and E. Vakkilainen¹

¹LUT University, School of Energy Systems, Yliopistonkatu 34, FI-53850 Lappeenranta, Finland
²Federal University of minas Gerais, Department of Chemical Engineering, Av. Antônio Carlos 6627, MG 31270-901 Belo Horizonte, Brazil
³Federal University of Viçosa, Department of Forest Engineering, Av. Peter Henry Rolfs, s/n - University Campus, MG 36570-900, Viçosa, Brazil
*Correspondence: clara.mendoza.martinez@lut.fi

Abstract:

The coffee production chain is a potential source of residual biomass inherent to the high productivity that can contribute to the generation of value-added products. The residues from the coffee sector are typically disposed to landfill without treatment causing potential environmental inconveniences. Briquetting presents an alternative process to produce a uniform fuel with high energy density. Briquettes facilitates easy transportation, enables better handling and storage of biomass residues. Properties such as low equilibrium moisture content, high energy density and compressive strength were reported for different coffee-pine wood briquettes treatments. Moreover, understanding of the thermal properties of the briquettes during combustion is crucial to evaluate their final application. This research is the first study that investigates the combustibility properties and kinetic parameters of the thermal decomposition of briquettes from coffee-pine wood using differential and integral thermal analysis under non-isothermal conditions. Multivariate analysis of the collected parameters through principal components analysis (PCA), was implemented to reduce the dimensionality of the data.
The desired profile in the combustibility is directly related to high temperatures and long burning times, thus, the tested briquettes displayed a significant combustibility potential, reporting peak temperatures and burnout times around 600 °C and 27 minutes, respectively. Activation energy kinetic parameter in the range of 12–42 kJ mol^-1 and average reactivity of 0.14–0.22 min^-1, were also found. The results revealed the not thermally hard material to degrade when compared to biomasses typically used for combustion.

Key words:

briquette, chemometrics, combustion rate, reactivity, solid biofuels