TRACE-METAL ANALYSIS; AQUEOUS-SOLUTION; MATRIX CONVERSION; HEAVY-METALS; LIBS; MEMBRANE; WATER; SPECTROMETRY; DEPOSITION; ADSORBENT

A highly concentrated, ring-shaped phase conversion (RSPC) method was developed for liquid sample analysis using the laser-induced breakdownspectroscopy (LIBS) technique. In this work, test samples were prepared by mixing the metal particles with polyvinyl alcohol (PVA) supporter in liquid phase. With heat, the PVA solution solidified inside a modified glass petri dish, forming a metal-enriched polymer ring film. Distinguished from other traditional liquid-to-solid conversing methods, the proposed new method takes advantage of enhanced homogeneity for the target elements inside the ring film. The modified glass petri dish was used to control the ring-shaped concentration. Due to the specially designed circular groove at the bottom of this dish, where the PVA solution and liquid sample mixture accumulated, the target elements were concentrated in this small ring, which is beneficial for enhancing and stabilizing the plasma signals compared to the direct liquid sample analysis using LIBS. The limits of detection for Ag, Cu, Cr, and Ba obtained with the RSPC-LIBS technology were 0.098 mu g . mL(-1), 0.18 mu g . mL(-1), 0.83 mu g . mL(-1), and 0.046 mu g . mL(-1), respectively, which provided greater improvement than the direct bulk liquid analysis using LIBS. (C) 2017 Optical Society of America

SURFACES; WATER; LIBS; SERS; IMPROVEMENT; ABLATION; SAMPLES; SENSOR; FLUIDS

In this study, we developed a substrate to enhance the sensitivity of LIBS by 5 orders of magnitude. Using a combination of field enhancement due to the metal nanoparticles in the substrate, the aggregate effect of super-hydrophobic interfaces and magnetic confinement, we performed a quantitative measurement of copper in solution with concentrations on the ppt level. We also demonstrated that the substrate improves quantitative measurements by providing an opportunity for internal standardization.

Laser-induced breakdown spectroscopy; LIBS; liquid; plasma; laser ablation;AQUEOUS-SOLUTIONS; VEGETABLE-OILS; WASTE-WATER; LIBS; METALS; ELEMENTS; SODIUM; PLASMA; PULSE; ACIDS

We studied changes in laser-induced breakdown spectroscopy (LIBS) signal intensity with the thickness of a liquid layer placed on a solid substrate, where an easily evaporating methanol sample was used. For a certain optimal liquid film thickness we obtained a manifold increase of the LIBS signal from methanol. Progressive liquid film thinning leads to a reduction and a successive disappearance of laser-induced splashes; the latter condition drastically reduces the sample consumption and allows measurements to be repeated many times on a single liquid droplet. In following, we developed two methods for actively controlled deformation, i.e., thinning of a liquid droplet (volume similar to 10 ml) prior to its sampling by LIBS. Control of the droplet's height was achieved on a Si-SiO2 wafer substrate by electro-wetting in the case of water solutions or by target rotation in the case of viscous liquids. The chosen substrate also has the advantages of low cost, easy manipulation, and very high purity, thus minimizing interference with analytes. Through the droplet deformation, in a single-pulse excitation at moderate laser energy (70 mJ), we clearly detected Fe and Mn in peanut oil, which represent trace elements in edible oils (similar to 1 part per billion), according to results published in the literature.

OPTICAL-EMISSION-SPECTROMETRY; TRACE-METAL ANALYSIS; AQUEOUS-SOLUTIONS; QUANTITATIVE-ANALYSIS; MATRIX CONVERSION; PHASE EXTRACTION; DIETHYLDITHIOCARBAMATE COMPLEXES; ELECTRICAL-DEPOSITION; SENSITIVE DETECTION; HEAVY-METALS

This work proposes a new development in the use of melted paraffin wax as a new extractant in a procedure designed to aggregate the advantages of liquid phase extraction (extract homogeneity, fast, and efficient transfer, low cost and simplicity) to solid phase extraction. As proof of concept, copper(II) in aqueous samples was converted into a hydrophobic complex of copper(II) diethyldithiocarbamate and subsequently extracted into paraffin wax. Parameters which X-100 concentration, vortex agitation time and affect the complexation and extraction (pH, DDTC, and Triton time) were optimized in a univariate way. The combination of the extraction proposed procedure with laser-induced breakdown spectroscopy allowed the precise copper determination (coefficient of variation = 3.1%, n = 10) and enhanced detectability because of the concentration factor of 18 times. A calibration curve was obtained with a linear range of 0.50-10.00 mg L-1 (R-2 = 0.9990, n = 7), LOD = 0.12 mg L-1, and LOQ = 0.38 mg L-1 under optimized conditions. An extraction procedure efficiency of 94% was obtained. The accuracy of the method was confirmed through the analysis of a reference material of human blood serum, by the spike and recovery trials with seawater, tap water, mineral water, and alcoholic beverages and by comparing with those results obtained by graphite furnace atomic absorption spectrometry.

Microconcentration; Optical spectroscopy; Measurement sensitivity; Portable analytical instrumentation;INDUCED BREAKDOWN SPECTROSCOPY; REAL-TIME MEASUREMENT; ELECTROSTATIC PRECIPITATOR; MASS-SPECTROMETRY; AERODYNAMIC LENS; VIRTUAL IMPACTOR; CONCENTRATOR; PARTICLES; DESIGN; EFFICIENCY

Efficient microconcentration of aerosols to a substrate is essential for effectively coupling the collected particles to microscale optical spectroscopies such as laser-induced or spark microplasma, or micro-Raman or infrared spectroscopies. In this study, we present detailed characterization of a corona-based aerosol microconcentration technique developed previously (Diwakar & Kulkarni, 2012). The method involves two coaxial electrodes separated by a few millimeters, one held at a high electrical potential and the other grounded. The particles are collected on the collection (i. e., ground) electrode from a coaxial aerosol flow in a one-step charge-and-collect scheme using corona discharge and electrical precipitation between the two electrodes. Performance of the corona microconcentration method was determined experimentally by measuring collection efficiency, wall losses, and particle deposition density. An intrinsic spectroscopic sensitivity was experimentally determined for the aerosol microconcentrator. Using this sensitivity, we show that corona-based microconcentration is much superior to alternative methods, including filtration, focused impaction using aerodynamic lens, and spot collection using condensational growth. The method offers unique advantages for compact, hand-held aerosol analytical instrumentation.

Laser-induced breakdown spectroscopy; Rare earth elements; Aqueous solution; Surface-enhanced;RARE-EARTH-ELEMENTS; QUANTITATIVE-ANALYSIS; ACCURACY IMPROVEMENT; EMISSION; SAMPLES; LIBS; EXTRACTION; LIQUIDS; WATER

Determination of rare earth elements (REEs) plays an important role in the extraction process. In this work, surface-enhanced laser-induced breakdownspectroscopy (SENLIBS) was introduced to detect REEs (lanthanum, cerium, praseodymium, and neodymium elements) in an aqueous solution. The emission lines of La II 394.91 nm, Ce II 418.66 nm, Pr II 422.29 nm, and Nd II 406.10 nm were selected for quantitative analysis by drying the analytical samples on a Zn metal substrate surface and optimizing the experimental parameters. The results showed that the limits of detection (LoDs) for determining La, Ce, Pr, and Nd elements can reach to 0.85, 4.07, 2.97, and 10.98 mu g mL(-1), respectively, which proved that SENLIBS is a feasible method for determining REEs.