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A comprehensive review is presented on the recent developments and trends in the QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation approach. This technique involves liquid-liquid partitioning using acetonitrile and purifying the extract using dispersive solid-phase extraction (d-SPE). Originally, the QuEChERS was introduced for pesticides residues analysis in high moisture fruits and vegetables, but more recently it is gaining significant popularity in the analysis of broad spectrum of analytes in huge variety of samples. The wide range of the technique applications is possible due to introducing various modifications based on the use of different extraction solvent and salt formulation and buffer additions for salting-out partitioning step and the application of various d-SPE sorbents for clean-up step. Therefore, the QuEChERS approach is useful for analysis of, among others pesticides, veterinary drugs and other pharmaceuticals, mycotoxins, polycyclic aromatic hydrocarbons (PAHs), dyes, acrylamide, synthetic musks and UV filters, bisphenols, polybrominated diphenyl ethers and other flame retardants, endocrine disruptors, and other chemical compounds. Thanks to the QuEChERS approach, high-throughput multiresidue methods operate in a routine contaminant control of food products, feedstuff, and environmental samples.
Laser-induced breakdown spectroscopy (LIBS) has been used as a remote sensing system to analyze seawater samples and to identify their salinities without ordinary calibration curves. The plasma is generated by focusing a pulsed Nd : YAG laser on the seawater surface in air at atmospheric pressure. Such plasma emission spectrum was collected using wide band fused-silica optical fiber of one-meter length connected to a portable Echelle spectrometer (Mechelle 7500 ? Multichannel Instruments, Stockholm, Sweden) with intensified CCD camera. Spectroscopic analysis of plasma evolution of laser produced plasmas has been characterized in terms of their spectra, electron density and electron temperature assuming the local thermodynamic equilibrium (LTE) and optically thin plasma conditions. Three elements Na, Ca and Mg were determined in the obtained spectra to identify the salinity of seawater samples. The electron temperature Te and density Ne were determined using the emission intensity and Stark broadening. The obtained values of Te and Ne for natural seawater sample (salinity 3.753%) are 11580 K ą 0.35% and 3.33×1018 cm?3 ą 14.3%. These values exhibit a significant change only if the matrix changes (i.e., the salinity changes). On the other hand, no significant difference was obtained if Te and Ne were determined using any of the three elements (Na, Ca and Mg) in the same matrix. It is concluded that Te and Ne represent a fingerprint plasma characterization for a given seawater sample and its salinity could be identified using only one element without need to analyze the rest of elements in the seawater matrix. The obtained results indicate that it is possible to improve the exploitation of LIBS in the remote on-line environmental monitoring, by following up only a single element as a marker to identify the seawater matrix composition and salinity without need to analyze that matrix which saves a lot of time and efforts.
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