Matrix andPUBLICATION NOTICE: Target Particle-Size Effects on LIBS Analysis of Soils

Link: http://dx.doi.org/10.21079/11681/35374

Report Number: ERDC/CRREL TR-20-1

Title: Matrix and Target Particle-Size Effects on LIBS Analysis of Soils

By Samuel A. Beal, Ashley M. Mossell, and Jay L. Clausen

Approved for Public Release; Distribution is Unlimited January 2020

ABSTRACT:  Laser-induced breakdown spectroscopy (LIBS) is a rapid, low-cost analytical method with potential applications in quantitative analysis of soils for major and trace elements. Here we examined the effects of matrix and target particle sizes on measurements of soil composition by LIBS. The experimental approach involved milling a clean sand matrix to six different particle sizes (medians: 19 to 810 µm) and spiking each with two different iron (Fe) minerals (medians: 1 and 74 µm) to a constant concentration of 5 wt%. The LIBS intensity of Fe emission lines decreased by 50% with increasing matrix processing and decreasing matrix particle size, regardless of spike. Conversely, emission lines of the matrix element silicon (Si) increased with decreasing matrix particle size. We hypothesized that this intensity effect was a result of changing surface concentrations, which was also apparent under visual inspection of the samples. Precision was acceptable for the 1 µm Fe spike in all matrices but required further puck milling and particle-size reduction for the larger Fe spike and for deter-mining Si content in both spikes and blanks. These results highlight the importance of matching matrix texture between standards and unknowns and of reducing particle size for quantitative LIBS analysis of soil.

27 pgs / 2.02 MB

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