Composition of inorganic components in <i>Helianthus tuberosus</i> stems

Abstract

This article studies inorganic components in Heliánthus tuberósus stems. Ash samples and extracts obtained at different pH values were examined. It is established that the extractant's nature has a significant effect on the yield of extractive substances from the ground stems: the greatest (45%) and the minimum (31%) yield was achieved by sodium hydroxide and distilled water, respectively. According to atomic absorption spectrometry, the main ions in the extracts obtained in different media are those of potassium, calcium, sodium, magnesium and iron. Following treatment of stems with solutions having different pH values, the mass fraction of ash varied from 0.4 to 2.3%. The smallest ash yield was observed for a stem sample after acid extraction. According to energy dispersive X-ray fluorescence spectrometry, all ash samples contained predominantly K, Ca, Si and P compounds. Acid hydrolysis produced the highest level of Si in samples, which allows this ash to be used as a silicon-containing material. The ash components of the core and outer part of the stem were compared with the initial sample. According to the nature of thermal decomposition, the initial sample and the outer shell were similar between themselves, though differing from the core. The ash content of the initial sample was 4.3%, with the ash content of the stem core being ~2 times higher than that of the outer shell (7 and 3.8%, respectively). The results of IR spectroscopy showed that splitting of bands in the IR spectra of ash samples depend on the part of the stem and the pre-treatment of raw materials at different pH values. The ash of the initial sample, core and outer shell, as well as the ash of the residues after the aqueous and alkaline hydrolysis of the stem, showed the absorption bands of carbonate groups. The IR spectra of the stem ash after acid extraction contained absorption bands characteristic of amorphous silicon dioxide. According to the conducted X-ray analysis, the studied ash samples were in an amorphous-crystal and crystalline state. The identification of phases was carried out.