Direct Quantitative Analysis of Particulate Aluminum Suspended in Water Using Laser-Induced Breakdown Spectroscopy

Abstract

Laser-induced breakdown spectroscopy (LIBS) has been developed as a rapid and easy in situ technique for the analysis of inorganic elements. Qualitative and quantitative determinations of an inorganic element can be achieved by analyzing the wavelength and intensity of the light emitted from the excited atoms arising from breakdown phenomena. Because the energy threshold of breakdown phenomena increases in the order of solid<liquid<gas, preferential breakdown of solid particles in liquid is possible by adjusting the energy of laser radiation. This rapid and easy in situ technique for the selective determination of soil particles or sediments suspended in water may enhance the effectiveness of environmental monitoring systems. In the present study, we applied LIBS to selective analyses of Al particles suspended in water. In addition, particle size effects that limit the performance of LIBS for the application of suspensions in the environment were investigated. Selective quantitative analysis of Al of gibbsite and alumina particles that were suspended in water was performed when the laser pulse energy was lower than that required for the breakdown of aqueous Al ions dissolved in water. When the Al concentration in the suspension was identical, the intensity of atomic emission from an Al particle increased with the particle size. This result was ascribed to the fact that larger particles contain more Al atoms per particle. There was a linear relationship between the cross-section area of the alumina particles and the intensity of the atomic emission per particle when the particles were small enough to exceed the threshold of breakdown. This suggested that both the particle size and Al concentration could be roughly estimated when simultaneous counting of the number of particles was accomplished by the use of laser-induced breakdown detection (LIBD).