Ionic-liquid-based microextraction method for the determination of silver nanoparticles in consumer products.

A simple method to determine hazardous silver nanoparticles (AgNPs) based on ionic liquid (IL) dispersive liquid-liquid microextraction and back-extraction is described. This approach involves AgNP stabilization using a cationic surfactant followed by extraction from the sample matrix by means of an IL as an extraction phase. Certain ILs have high affinity for metals, and preliminary experiments showed that those ILs consisting of imidazolium cation efficiently extracted AgNPs in the presence of a cationic surfactant and a chelating agent. Afterward, histamine was used as a dispersing agent to promote phase transfer of differently coated AgNPs from the IL in aqueous solution to be subsequently analyzed by UV-visible spectrometry. The analytical procedure allows AgNPs to be recovered from the sample matrix in an aqueous medium, the enrichment factor being up to 4, preserving both AgNP size and AgNP shape as demonstrated by transmission electron microscopy images and the localized surface plasmon resonance band characteristic of each AgNP. The present method exhibited a linear response for AgNPs in the range from 3 to 20 µg/mL, the limit of detection being 0.15 µg/mL. Method efficiency was assessed in spiked orange juice and face cream, yielding recoveries ranging from 75.7% to 96.6%. The method was evaluated in the presence of other nanointerferents (namely, gold nanoparticles). On the basis of diverse electrophoretic mobilities and surface plasmon resonance bands for metal nanoparticles, capillary electrophoresis was used to prove the lack of interaction of the target AgNPs with gold nanoparticles during the whole protocol; thus, interferents do not affect AgNP determination. As a consequence, the analytical approach described has great potential for the analysis of engineered nanosilver in consumer products. Graphical abstract Simple protocol for the determination of silver nanoparticles (AgNPs) based on dispersive liquid-liquid extraction with a specific short alkyl side chain ionic liquid and their quantitative detection with a UV-visible spectrometer. HMIM•PF6 1-hexyl-3-methylimidazolium hexafluorophosphate, NP nanoparticle, SPR surface plasmon resonance.

Cyclodextrin-modified nanodiamond for the sensitive fluorometric determination of doxorubicin in urine based on its differential affinity towards ß/γ-cyclodextrins.

The manuscript reports on the preparation of ß-cyclodextrin-modified nanodiamonds (ßCD-ND) for the extraction and preconcentration of the fluorescent anticancer drug doxorubicin (DOX) from biological samples. The inclusion of DOX into the cavities of ß- and γ-cyclodextrin (CD) confirms their utility for selective extraction and elution of the drug based on its good fit to the cyclodextrin cavity. Although both larger cyclodextrins (ßCD and γCD) accommodate DOX, DOX clearly prefers the bigger γCD cavities. Dispersive micro solid-phase extraction using ßCD-ND as sorbent enables the inclusion complexation of DOX. The elution of DOX from ßCD-ND cavities occurs with a basic solution of γCD containing 10% acetonitrile owing to the preferential affinity (i.e. optimal fit) of DOX into the larger γCD cavity. DOX is quantified by monitoring its intrinsic fluorescence (exc/em = 475/595 nm). The method can determine DOX in urine with a limit of detection of 18 ng·mL-1. Recoveries (93.2% and 94.0%) and precision (RSDs of 5.9% and 4.7%) at 100 and 400 ng·mL-1 DOX levels in urine are satisfactory. The matrix effect is negligible even when working with undiluted urine samples. Graphical abstract Nanodiamonds functionalized with ß-cyclodextrin (ßCD-ND) were used as sorbent for the determination of nanomolar levels of doxorubicin (DOX). It is based on host:guest interactions ruled by different stabilities of DOX within cyclodextrin (CD) cavity-size: ßCD/γCD.

Fluorescent nanocellulosic hydrogels based on graphene quantum dots for sensing laccase.

A novel low-cost fluorimetric platform based on sulfur, nitrogen-codoped graphene quantum dots immersed into nanocellulosic hydrogels is designed and applied in detecting the laccase enzyme. Although most of methods for detecting laccase are based on their catalytic activity, which is strongly dependent on environmental parameters, we report a sensitive and selective method based on the fluorescence response of hydrogels containing graphene quantum dots (GQDs) acting as luminophore towards laccase. The easily-prepared gel matrix not only improves the fluorescence signal of GQDs by avoiding their self-quenching but also stabilizes their fluorescence signal and improves their sensitivity towards laccase. Noncovalent interactions between the sensor and the analyte are believed to be causing this significant quenching without peak-shifts of GQD fluorescence via energy transfer. The selective extraction of laccase was proved in different shampoos as complex matrices achieving a detection limit of 0.048 U mL-1 and recoveries of 86.2-94.1%. As the unusual properties of nanocellulose and GQDs, the fluorescent sensor is simple, eco-friendly and cost-efficient. This straightforward strategy is able to detect and stabilize laccase, being an added-value for storage and recycling enzymes.

Pharmaceutical crystallization with nanocellulose organogels.

Carboxylated nanocellulose forms organogels at 0.3 wt% in the presence of a cationic surfactant. The resulting gels can be used as novel crystallization media for pharmaceutical solid form control, resulting in isolation a new sulfapyridine solvate, morphology modification and crystallization of an octadecylammonium salt of sulfamethoxazole.

Sulfonated nanocellulose for the efficient dispersive micro solid-phase extraction and determination of silver nanoparticles in food products.

This paper reports a simple approach to Analytical Nanoscience and Nanotechnology (AN&N) that integrates the nanotool, sulfonated nanocellulose (s-NC), and nanoanalyte, silver nanoparticles (AgNPs), in the same analytical process by using an efficient, environmentally friendly dispersive micro solid-phase extraction (D-µSPE) capillary electrophoresis (CE) method with s-NC as sorbent material. Introducing negatively charged sulfate groups onto the surface of cellulose enhances its surface chemistry and enables the extraction and preconcentration of AgNPs of variable diameter (10, 20 and 60nm) and shell composition (citrate and polyvinylpyrrolidone coatings) from complex matrices into a cationic surfactant. In this way, AgNPs of diverse nature were successfully extracted onto the s-NC sorbent and then desorbed into an aqueous solution containing thiotic acid (TA) prior to CE without the need for any labor-intensive cleanup. The ensuing eco-friendly D-µSPE method exhibited a linear response to AgNPs with a limit of detection (LOD) of 20µg/L. Its ability to specifically recognize AgNPs of different sizes was checked in orange juice and mussels, which afforded recoveries of 70.9-108.4%. The repeatability of the method at the limit of quantitation (LOQ) level was 5.6%. Based on the results, sulfonated nanocellulose provides an efficient, cost-effective analytical nanotool for the extraction of AgNPs from food products.

ß-Cyclodextrin decorated nanocellulose: a smart approach towards the selective fluorimetric determination of danofloxacin in milk samples.

An innovative and versatile strategy of Solid Phase Microextraction (SPME) is shown by using a new type of ß-cyclodextrin-modified nanocellulose (CD-NC) as a sorbent material. ß-cyclodextrin (used as an inclusion-type selector) was covalently bonded to amine-modified nanocellulose by an amidation reaction. Such novel nanocavities were successfully applied to the selective recognition of danofloxacin (DAN), an antibiotic used to treat animal diseases, via supramolecular host-guest interactions. The SPME methodology, using a platform based on ß-cyclodextrin-"decorated" nanocellulose as a sorbent material, showed a wide linear fluorimetric response against DAN from 8 to 800 µg L(-1) and a detection limit of 2.5 µg L(-1). The specific recognition of DAN has been proven to be highly selective and efficient against this metabolite and other fluoroquinolones. The reusability and the high efficiency in the extraction and preconcentration of DAN in milk samples allow recoveries of 94%.

Ternary composites of nanocellulose, carbonanotubes and ionic liquids as new extractants for direct immersion single drop microextraction.

We proposed for the first time the use of Nanocellulose (NC) into a single drop for extracting and preconcentrating a heterocyclic amine (HCA) in fried food. In conventional single-drop microextraction (SDME) techniques, ionic liquids (IL) or other organic solvents cannot extract HCAs due to its polarity. The advantageous combination of nanomaterials and nanohybrids based on NC and multiwalled carbonanotubes (MWCNT) with IL allows the preparation of a stable droplet with an excellent and selective ability for the preconcentration of the mutagenic 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) by the simple direct immersion SDME technique. The main variables involved in the extraction and preconcentration steps have been evaluated and optimized. The developed method was found to achieve a linear calibration curve in the concentration range of 0.1-10 mg L(-1) (r(2)=0.998), with a detection limit (LOD) of 0.29 mg L(-1). Recovery of the method, which was studied in quintuplicate in sausage samples, varied from 90.1% to 95.3% for MeIQx.