In this paper, we report a study about the application of packaged fiber Bragg gratings used as strain sensors to monitor the stress kinetics during the drying process of commercial latex paints. ...Three stages of drying with distinct mechanical deformation and temporal behaviors were identified for the samples, with mechanical deformation from 15 μm to 21 μm in the longitudinal film dimension on time intervals from 370 to 600 minutes. Drying time tests based on human sense technique described by the Brazilian Technical Standards NBR 9558 were also done. The results obtained shows that human sense technique has a limited perception of the drying process and that the optical measurement system proposed can be used to characterize correctly the dry-through stage of paint. The influence of solvent (water) addition in the drying process was also investigated. The paint was diluted with four parts paint and one part water (80% paint), and one part paint and one part water (50% paint). It was observed that the increase of the water ratio mixed into the paint decreases both the mechanical deformation magnitude and the paint dry-through time. Contraction of 5.2 μm and 10.4 μm were measured for concentrations of 50% and 80% of paint in the mixture, respectively. For both diluted paints the dry-through time was approximately 170 minutes less than undiluted paint. The optical technique proposed in this work can contribute to the development of new standards to specify the drying time of paint coatings.
Electromembrane extraction (EME) is a miniaturized technique in which charged molecules are extracted from biological samples, through a porous membrane, into an acceptor solution. This process ...occurs in the presence of an electric field that enables increased analyte recovery in short extraction times. Studies are being carried out to establish recommended extraction conditions for different groups of compounds based on their physicochemical properties. In this work, pre-established generic liquid membranes for the extraction of basic compounds were tested using synthetic cathinones within a wide log P range as basic model analytes. First, recommended organic solvents for the chosen analytes were evaluated in terms of recovery. The best candidates were included in an optimization study with other relevant EME conditions (voltage, extraction time, and agitation rate). All analyses were performed using a UPLC-MS/MS with the multiple reaction monitoring mode. 2-Undecanone was chosen as the liquid membrane providing the best extraction efficiency in combination with 40 V, 35 min, and 725 rpm. Validation showed r2 > 0.99 in the 1–500 ng/mL range, accuracy of ±12%, imprecision of ≤19%, 1 ng/mL as limit of quantitation, 0.1–0.5 ng/mL as limit of detection, matrix effect 97–118%, and recovery 63–110%. Among the generic liquid membranes studied in this work, 2-Undecanone was the best choice for the target basic analytes. High recoveries and low matrix effects were achieved, thus demonstrating the applicability of recommended generic liquid membranes in the 96-well plate setup and with whole blood samples. Our findings contribute to further establishing EME as an actual sample preparation technique for routine analyses that could be further explored in a commercial format.
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•The performance of EME on a prototype 96-well plate setup was studied.•The applicability of generic SLM for basic compounds was evaluated.•Synthetic cathinones were the model basic analytes extracted from whole blood.•NPOE+6 MC:Thy and 2-Undecanone were the best SLM for the target compounds.•Further consolidating EME as a green and efficient technique for routine analyses.
This work describes a method for producing a nanostructured fiber optic device for sensing of pesticides in water environment. The device consists of a long period grating with a coating of gold ...nanoparticles functionalized with cysteamine. The LPG shows attenuation bands near the phase matching turning point at the visible spectral range. A bottom-up production route was used to deposit gold nanoparticles on the fiber surface. Sensitivity to the refractive index of the external medium was measured before and after the layer deposition. Cysteamine was used as a ligand for glyphosate present in water at a concentration of 100 μM.
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