Matrix effects on laser-induced plasma parameters for soils and oresстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 3 ноября 2018 г.
Аннотация:Matrix effects caused by either physical properties or chemical nature of a sample are the main analytical problems of laser-induced breakdown spectroscopy responsible for worsening of accuracy. We have studied a relation of laser plasma parameters and three intrinsic properties of powders for soils and ores: (i) sample moisture content; (ii) compressive force for sample pelleting; (iii) total content of easily ionized elements (EIEs). We prepared three sets of soils (calcareous, black, and sod-podzol) with different moisture content (from 0% to 8% wt.) by saturation of dried powders with water vapor. Moisture of soils did not influence plasma temperature and its electron density, while the intensity of particular emission line (Mn I 403.08 nm) had two opposite trends for the black and sod-podzol soils, decreasing with moisture content, and increasing for the gray calcareous soil. The latter seems to be due to cementation of Ca-rich soil. A fine-dispersed powder of ferromanganese nodules was compressed by application of compressive force ranged in 0–10 tons/cm2 to investigate its influence on plasma parameters. Electron density increased in several times with the growth of compressive force that was mostly expressed at longer delays (7.5 μs). Although the compressive force had not such a strong influence on plasma temperature, we demonstrated that a short delay (0.5–1 μs) provided minimal changes in plasma parameters. The variation of EIEs content (0.5–13% wt.) in the used certified samples allowed investigation of the EIEs effect. Electron density was similar for a relatively low content (<5% wt.), while electron density increased in several times for high content of EIEs. Plasma temperature did not clearly depend on soil types or EIEs content. We concluded that EIEs content mostly influences on ionization equilibrium.