Direct determination of Cu, Cr, and Ni in river sediments using double pulse laser-induced breakdown spectroscopy: Ecological risk and pollution level assessment.

Double pulse laser-induced breakdown spectroscopy (DP LIBS) has attracted much attention for analyzing trace elements due to its higher sensitivity when compared to single pulse laser-induced breakdown spectroscopy (SP LIBS). However, the development of quantitative methods in LIBS for the analysis of complex samples, such as sediments, is a great challenge due to the matrix effects that are very accentuated in this technique. In this study, different spectral treatments and calibration strategies were investigated to obtain calibration models that allow determinations with satisfactory accuracy and precision of Cr, Cu, and Ni in river sediments from different hydrographic basins. The best model developed for Cr was using MMC without spectral normalization and for Cu and Ni it was using MMC with spectral normalization, and using inverse regression, an increase in the accuracy of the determinations of all analytes was obtained. These models showed limit of quantification (LOQ) of 7.87 mg kg-1, 1.62 mg kg-1, and 2.21 mg kg-1 and root mean square error of prediction (RMSEP) of 7.54 mg kg-1, 14.53 mg kg-1, and 8.29 mg kg-1 for Cr, Cu, and Ni, respectively. Therefore, the models have adequate sensitivity and precision for the quantification of the potentially toxic elements (PTEs) evaluated, since, according to Brazilian legislation, the lower concentration of threshold effect level (TEL) for Cr, Cu, and Ni is <37.3 mg kg-1, <35.7 mg kg-1, and <18 mg kg-1, respectively. The concentrations of Cr, Cu, and Ni determined by DP LIBS allowed to obtain a partial ecological risk assessment of the studied sediments. Also, the chemometric tool Kohonen self-organizing map (KSOM) were used for data interpretation.

Direct determination of nutrient elements in plant leaves by double pulse laser-induced breakdown spectroscopy: evaluation of calibration strategies using direct and inverse models for matrix-matching.

This study aims to develop a single calibration model to determine nutrient elements directly (Ca, Mg, Mn, and P) in soybean and sugar cane leaf samples by double pulse laser-induced breakdown spectroscopy (DP LIBS). Matrix-matching calibration (MMC) was evaluated using direct and inverse models. Forty-five samples were used to build the calibration model (23 soybean leaves and 22 sugar cane leaves), and fifteen were used for the prediction test (8 soybean leaves and 7 sugar cane leaves) models. In the direct model, the analyte concentration in the sample is the independent variable, and the analytical signal is the dependent variable. In the inverse model, the analytical signal is the independent variable, and the analyte concentration in the sample is the dependent variable. In general, both models presented satisfactory results; however, the inverse model performed better. Emission lines used to propose calibration models were selected using a linear Pearson's correlation (R) strategy between each spectral point and the Ca, Mg, Mn, and P concentration measured by reference methods using inductively coupled plasma optical emission spectrometry (ICP OES). The root mean square errors of prediction (RMSEP) for the direct models were 0.60 g kg-1 to (Ca), 0.47 g kg-1 (Mg), 9.3 mg kg-1 to (Mn), and 0.28 g kg-1 to (P); for inverse model was 0.55 g kg-1 to (Ca), 0.39 g kg-1 (Mg), 10.5 mg kg-1 to (Mn), and 0.21 g kg-1 to (P). The calibration strategies proposed in this study may minimize matrix effects in direct solid analysis in soybean and sugar cane leaf samples, performing the determination of Ca, Mg, Mn, and P by DP LIBS using a single calibration model.

Application of the experimental design in the optimization of a procedure for antimony (Sb) remediation in environmental samples employing mesoporous array.

This study describes the sustainable and eco-friendly synthesis of the silica-based mesoporous structure from the use of alternative amorphous silica extracted from rice husk ash (RHA). The mesoporous material was called MCM-48 (RHA), and its application as adsorbent to the antimony (Sb) remediation in environmental samples was tested. The adsorbent was prepared by an efficient and sustainable hydrothermal method, which exhibited an amorphous framework with type IV isotherms and type H1 hysteresis, and surface area, total pore volume, and pore diameter values of 820.9 m2 g-1, 0.6 cm3 g-1, and 3.7 nm, respectively. In addition, the MCM-48 (RHA) exhibited a three-dimensional cubic mesostructure (Ia3d space-group symmetry) with a narrow mesopore distribution, uniform spherical particles, and well-defined architecture. Multivariate optimization using a factorial design (24) was employed in the adsorption tests of Sb. The variables evaluated and the optimum conditions obtained were (i) adsorbent mass (45 mg); (ii) adsorption time (115 min); (iii) pH 2; and (iv) Sb initial concentration of 8 mol L-1. In these conditions, we found a maximum adsorption efficiency of Sb in the order of 95%. The adsorbent material proposed in this study proved to be efficient for Sb remediation in water samples under different experimental conditions. A total of five samples were analyzed and Sb concentrations on the order of 8 ppm were added, in which a removal efficiency of Sb raging between 88 and 96% was obtained for the remediation in real samples. In addition, the low cost of the synthesis of MCM-48 (RHA) in combination with its high and fast adsorption capacities offers a great promise for wastewater remediation, which makes it very attractive for environmental approaches.

Direct determination of Ca, K, Mg, Na, P, S, Fe and Zn in bivalve mollusks by wavelength dispersive X-ray fluorescence (WDXRF) and laser-induced breakdown spectroscopy (LIBS).

This study aims to develop methods for determination of Ca, K, Mg and Na by laser-induced breakdown spectroscopy (LIBS) and Ca, K, Mg, Na, P, S, Fe and Zn by wavelength dispersive X-ray fluorescence (WDXRF) in pressed pellets bivalve mollusks. LIBS and WDXRF calibration models were built with references values determined by inductively coupled plasma optical emission spectrometry (ICP OES) after acid digestion. The calibration models for LIBS and WDXRF were obtained from 28 samples (14 for calibration and 14 for validation). It was possible to implement a validation between LIBS and WDXRF methods for elements Ca, K, Mg and Na. The proposed calibration model obtained using LIBS and WDXRF data presented a good correlation with reference values obtained by ICP OES.

Determination of toxic metals in leather by wavelength dispersive X-ray fluorescence (WDXRF) and inductively coupled plasma optical emission spectrometry (ICP OES) with emphasis on chromium.

The tanning industry is one of the largest environmental polluters due to high generation waste in all production processes, but the tanning is particularly worrisome due to the use of significant amounts of chromium. Cr is an element potentially toxic to both health and the environment, depending on the concentration and the oxidation state. Cr(VI) can come in contact with human skin when using leather goods, which can cause allergies and dermatitis, besides being carcinogenic. Considering that approximately 90% of the world production of leather is performed with Cr salts, the determination of this element in leather is necessary to avoid exposure to the risks that the element can provide. The main goal of this study was the development of an alternative analytical method for the determination of Cr in leathers (ovine and bovine leather tanned with Cr and vegetable tannin) using wavelength dispersive X-ray fluorescence (WDXRF) for direct solid analysis. Besides performing analysis of the chemical composition and determination of Al, As, Ba, Ca, Cd, Cr, Cu, Fe, Mg, Ni, Pb, Sb, Sr, Ti, and Zn in leather by inductively coupled plasma optical emission spectrometry (ICP OES). Principal component analysis (PCA) was also used in the evaluation of the WDXRF and ICP OES data sets. WDXRF calibration models for Cr presented satisfactory figures of merit and the analysis of the leathers revealed an alarming concentration of total Cr in the samples reaching 21,353 mg kg-1.

Use of laser-induced breakdown spectroscopy for the determination of polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) concentrations in PC/ABS plastics from e-waste.

Due to the continual increase in waste generated from electronic devices, the management of plastics, which represents between 10 and 30% by weight of waste electrical and electronic equipment (WEEE or e-waste), becomes indispensable in terms of environmental and economic impacts. Considering the importance of acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), and their blends in the electronics and other industries, this study presents a new application of laser-induced breakdown spectroscopy (LIBS) for the fast and direct determination of PC and ABS concentrations in blends of these plastics obtained from samples of e-waste. From the LIBS spectra acquired for the PC/ABS blend, multivariate calibration models were built using partial least squares (PLS) regression. In general, it was possible to infer that the relative errors between the theoretical or reference and predicted values for the spiked samples were lower than 10%.

Multivariate optimization of simple procedure for determination of Fe and Mg in cassava starch employing slurry sampling and FAAS.

A slurry sampling procedure has been developed for Fe and Mg determination in cassava starch using flame atomic absorption spectrometry. The optimization step was performed using a univariate methodology for 200mg samples and a multivariate methodology, using the Box-Behnken design, for other variables, such as solvent (HNO3:HCl), final concentration (1.7molL-1) and time (26min). This procedure allowed determination of iron and magnesium with detection limits of 1.01 and 3.36mgkg-1, respectively. Precision, expressed as relative standard deviation (%RSD), was of 5.8 and 4.1% (n=10) for Fe (17.8mgkg-1) and Mg (64.5mgkg-1), respectively. Accuracy was confirmed by analysis of a standard reference material for wheat flour (NIST 1567a), which had certified concentrations of 14.1±0.5mgkg-1 for Fe and 40±2.0mgkg-1 for Mg, and the concentrations found using proposed method were 13.7±0.3mgkg-1 for Fe and 40.8±1.5mgkg-1 for Mg. Comparison with concentrations obtained using closed vessel microwave digestion was also realized. The concentrations obtained varied between 7.85 and 17.8mgkg-1 for Fe and 23.7-64.5mgkg-1, for Mg. The simplicity, easily, speed and satisfactory analytical characteristics indicate that the proposed analytical procedure is a good alternative for the determination of Fe and Mg in cassava starch samples.