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The acoustic wave produced alongside laser-induced plasmas can be used in conjunction with the recorded atomic spectra of plasma emission to expand the physicochemical information acquired from a single inspection event. Among the most interesting uses of acoustic information is the differentiation of mineral phases with similar optical responses coexisting in geological targets. In addition, laser-induced plasma acoustics (LIPAc) can provide data related to the inspected material's hardness, density, and compactness. In this paper, we present a dual acoustic–optic laser-based strategy for the generation of high-resolution surface images of mineral samples. By combining simultaneous multimodal LIBS (laser-induced breakdown spectroscopy) and LIPAc spectral data from laser-induced plasmas, we explore the mineralogical composition of rocks embedded in resin matrixes to distinguish their chemical composition as well as their crystal phases based on physical changes caused by the different spatial arrangements of the constituent atoms. The multispectral polyhedron created by merging singular optical maps, one per detected elements, and the coincidental acoustic map enhance the distinction between regions present within the matrix of a host rock as compared to the differentiation yielded by each technique when used separately. The chemical information guides the composition of the mineral phases in the host rock. Then, the physical information obtained from acoustics may reinforce the identification of the detected mineral phase, draw the geological history of the inspected section, and showcase possible transformations, mainly of polymorphic nature. To test the combination proposed herein, we also inspected a septarian nodule featuring an ensemble of mineral phases with different origins. Mixed optical and acoustic responses from laser-produced plasmas of this complex sample allowed us to obtain more specific information. This approach constitutes a reliable and high-throughput tool for studying the surface of geological samples, which can substantially supplement well-established techniques for mineralogical analysis such as Raman spectroscopy and X-ray diffraction.

The shockwave produced alongside the plasma during a laser-induced breakdown spectroscopy event can be recorded as an acoustic pressure wave to obtain information related to the physical traits of the inspected sample. In the present work, a mid-level fusion approach is developed using simultaneously recorded laser-induced breakdown spectroscopy (LIBS) and acoustic data to enhance the discrimination capabilities of different iron-based and calcium-based mineral phases, which exhibit nearly identical spectral features. To do so, the mid-level data fusion approach is applied concatenating the principal components analysis (PCA)-LIBS score values with the acoustic wave peak-to-peak amplitude and with the intraposition signal change, represented as the slope of the acoustic signal amplitude with respect to the laser shot. The discrimination hit rate of the mineral phases is obtained using linear discriminant analysis. Owing to the increasing interest for in situ applications of LIBS + acoustics information, samples are inspected in a remote experimental configuration and under two different atmospheric traits, Earth and Mars-like conditions, to validate the approach. Particularities conditioning the response of both strategies under each atmosphere are discussed to provide insight to better exploit the complex phenomena resulting in the collected signals. Results reported herein demonstrate for the first time that the characteristic sample input in the laser-produced acoustic wave can be used for the creation of a statistical descriptor to synergistically improve the capabilities of LIBS of differentiation of rocks.

Nanosecond laser-induced breakdown spectroscopy has been examined for the analysis of suspended matter in a free stream of air. The real-time monitoring of this scenario poses major challenges for an accurate categorization due to its changing characteristics such as composition, size, and density of particles. The effects of particle size and matrix in the optical emission responses registered from such scenarios have been evaluated. Distant (10 m) plasmas of saline solutions, containing either NaCl or Na_2SO_4 at different concentrations, have been induced by nanosecond laser pulses at a wavelength of 1064 nm. The effects of the droplet size and its concentration on differences in the laser-induced breakdown probability, the intensity of the characteristic lines, and the plasma emission continuum have been discussed. The quantification of sodium in distant water droplets has been proved. However, an initial knowledge on the average droplet size is required. The average droplet size could be determined from the slope of H I and O I lines versus the continuum plasma emission, which is only weakly influenced by the salt content in the droplets.

An automated procedure has been developed for Fourier transform near infrared (FT-NIR) determination of buprofezin in pesticide formulations. This methodology is based on on-line pesticide extraction with acetonitrile from solid samples and its determination by using peak area absorbance measurements between 2147 and 2132 nm, corrected with a horizontal baseline established at 2091 nm. The repeatability, as a relative standard deviation of five independent analyses of 18.9 mg g−1of buprofezin, was 0.06% and the limit of detection 5 mg L−1. The reagent consumption was clearly reduced compared with a chromatographic reference procedure from 40.4 mL acetonitrile per sample, required by high performance liquid chromatography (HPLC), to 2 mL acetonitrile consumed for FT-NIR. The sample measurement throughput obtained by the FT-NIR methodology was 30 h−1, five times higher than that obtained by HPLC (6 h−1). It can be concluded that the proposed vibrational spectroscopic method is appropriate for the quality control of commercial pesticide formulations. The on-line sample treatment avoids contact by the operator with toxic products and this method is an environmentally friendly alternative to the measurement in the mid infrared which requires the use of CHCl3.

An automated procedure has been developed for Fourier transform near infrared (FT-NIR) determination of buprofezin in pesticide formulations. This methodology is based on on-line pesticide extraction with acetonitrile from solid samples and its determination by using peak area absorbance measurements between 2147 and 2132 nm, corrected with a horizontal baseline established at 2091 nm. The repeatability, as a relative standard deviation of five independent analyses of 18.9 mg g^−1 of buprofezin, was 0.06% and the limit of detection 5 mg L^−1. The reagent consumption was clearly reduced compared with a chromatographic reference procedure from 40.4 mL acetonitrile per sample, required by high performance liquid chromatography (HPLC), to 2 mL acetonitrile consumed for FT-NIR. The sample measurement throughput obtained by the FT-NIR methodology was 30 h^−1, five times higher than that obtained by HPLC (6 h^−1). It can be concluded that the proposed vibrational spectroscopic method is appropriate for the quality control of commercial pesticide formulations. The on-line sample treatment avoids contact by the operator with toxic products and this method is an environmentally friendly alternative to the measurement in the mid infrared which requires the use of CHCl_3.