0000000000004750
AUTHOR
Soledad Cárdenas
One-pot synthesis of graphene quantum dots and simultaneous nanostructured self-assembly via a novel microwave-assisted method: impact on triazine removal and efficiency monitoring
One-step methods for fabricating green materials endowed with diverse functions is a challenge to be overcome in terms of reducing environmental risk and cost. We report a fast and easy synthesis of multifunctional materials composed of only fluorescent dots with structural flexibility and high sorption capability. The synthesis consists of a one-pot microwave-assisted reaction for the simultaneous formation of graphene quantum dots (GQDs) from organic precursors and their spontaneous self-assembly forming porous architectures. The GQD-assemblies are robust and no signs of degradation were observed with most organic solvents. The ensuing GQDs and their porous solids were fully characterized…
Carbon fibers as green and sustainable sorbent for the extraction of isoflavones from environmental waters.
Abstract Isoflavones are a group of phytoestrogens of important environmental concern due to their endocrine disrupting effects. This article presents a rapid, green, and sustainable method for determining four isoflavones (daidzein, genistein, formononetin, and biochanin A) in environmental waters complying with current trends in Analytical Chemistry. The method consists of in-syringe dispersive solid-phase extraction (DSPE) as the extraction approach, using carbon fibers as extraction material. The synthesis of carbon fibers is simple and sustainable, since it only requires a natural product such as raw cotton as precursor, which is thermally treated (600 °C for 30 min) in an inert (Ar) a…
FI automatic method for the determination of copper(II) based on coproporphyrin I-Cu(II)/TCPO/H(2)O(2) chemiluminescence reaction for the screening of waters.
Abstract In this paper, an automatic method for the screening of water samples containing Cu(II) was proposed, based on peryoxalate chemiluminescence reaction using coproporphyrin I as fluorophor compound to provide selectivity and a simple flow injection (FI) chemiluminescence detector (CLD). FI system conditions were chosen in order to distinguish samples over or under legislation limit established (50 μg l−1) with high reliability. The detection limit found was 9 μg l−1 and the linear dynamic range was 15–125 μg l−1 of Cu(II). Repeatibility and reproducibility studies gave good precision and accuracy with recovery near 100%. Under these conditions, the method resulted selective and only …
Synergistic combination of polyamide-coated paper-based sorptive phase for the extraction of antibiotics in saliva.
Abstract The development of analytical methods that allow the simultaneous determination of a wide range of analytes with different properties is one of the focuses of attention in Analytical Chemistry. This work describes a proof-of-concept of the synergistic extraction of a planar paper-based sorptive phase modified with a polyamide such as nylon. This as-prepared sorptive phase enables the extraction of six penicillin-derived antibiotics of different polarity from human saliva samples in the same analysis, since the analytes either interact with the paper or with the nylon. The synthesis of the sorptive phase is simple as it only requires dipping the paper into an organic solution of the…
Sensitive determination of polycyclic aromatic hydrocarbons in water samples using monolithic capillary solid-phase extraction and on-line thermal desorption prior to gas chromatography-mass spectrometry.
A methacrylate-based monolithic capillary column has been evaluated for the preconcentration of polycyclic aromatic hydrocarbons (PAHs) from environmental water samples. For this purpose, the monolyte was in situ synthesized in a 6cm×0.32mm id fused-silica capillary. The microextraction unit was fitted to a micro-HPLC pump to pass 10mL of sample. The isolated pollutants were eluted by means of 10μL of methanol, the organic phase being directly collected in a specific interface that can be fitted to the injection port of the gas chromatograph without modification. The interface allows the on-line thermal desorption of the PAHs, avoiding the dilution and providing enough sensitivity to reach …
Ultrafast spectroscopic investigation on fluorescent carbon nanodots: the role of passivation.
Disentangling the respective roles of the surface and core structures in the photocycle of carbon nanodots is a critical open problem in carbon nanoscience. While the need of passivating carbon dot surfaces to obtain efficiently emitting nanoparticles is very well-known in the literature, it is unclear if passivation introduces entirely new surface emitting states, or if it stabilizes existing states making them fluorescent. In this multi-technique femtosecond spectroscopy study, the relaxation dynamics of non-luminescent (non-passivated) carbon dots are directly compared with their luminescent (passivated) counterparts. Non-passivated dots are found to host emissive states, albeit very sho…
Dispersive micro-solid phase extraction
Abstract Dispersive micro-solid phase extraction (D-μSPE) has gained special attention in the sample preparation process due to its simplicity, speed and efficiency. Different dispersion approaches have been used within this technique to allow a close contact between the sorbent and the donor sample solution during the entrapping step, but also between the sorbent and the solvent in the elution step. This dispersion favors the kinetics of both sorption and elution and therefore increases the efficiency of the overall extraction procedure. This technique boasts of high versatility owing to the great variety of solids available, covering a high range of chemical functionalities. This article …
Carbon nanostructures incorporated on methacrylate monoliths for separation of small molecules by nano-liquid chromatography
Abstract Carbon nanostructures have been incorporated to polymethacrylate monoliths to develop novel stationary phases with enhanced separation performance in nano-liquid chromatography (nano-LC). Two incorporation approaches of these nanomaterials in monoliths were investigated. Single-walled carbon nanohorns (SWNHs) were first incorporated to the polymerization mixture, followed by UV initiation. The resulting stationary phases with embedded SWNHs led to an increase in the separation performance of analytes compared to the parent monolith. Alternatively, a two-step photo-grafting approach was also adopted to attach the carbon nanoparticles onto the polymer monolith surface. The effect of …