Influence of sample matrix and filter fixation on LIBS signal in analysis of algae on filter

This study first reveals the matrix effect mechanism of filter fixation on laser-induced breakdown spectroscopy (LIBS) quantitative analysis of algae, providing a methodological reference for in situ environmental detection. A collinear 1064 nm double pulse LIBS was used for analysis of green algae on a cellulose filter. Intensities of the contaminant elements Zn, Ni and those of some matrix lines of C I, Ca I, II, K I, Mg I, II, Mn I, II, Na I, H I, O I were measured and compared for various numbers of tape layers used for the filter fixation onto a microscope glass slide. This arrangement simulated surface modifications which can substantially lower the measured intensities. Maximum intensities were measured for 1 or 2 tape layers and lowest intensities for 6 layers for filters with contaminated algae; however, this intuitive result was not yielded for non-contaminated algae. It might indicate substantial changes of the filter properties and interaction with the laser beam at minimal changes of the analyte. This is crucial for quantitative analysis influenced not only by the sample fixation and surface quality but also by the composition of the filtered algae. The results were, to some extent, supported by principal component analysis, a shadowgraphic study of a single pulse microplasma shockwave, crater size and by simplified geometric and thermodynamic models. These were based on a spherical shape and full validity of the Boltzmann distribution respectively. The relatively small changes of the abovementioned parameters are in contrast to important changes of the lines intensities measured from the microplasma on the contaminated samples.