Non-aqueous capillary electrophoresis separation of fullerenes and C60 fullerene derivatives

As the interest in the use of fullerene compounds in biomedical and cosmetic applications increases, so too does the need to develop methods for their determination and quantitation in such complex matrices. In this work we studied the behavior of C60 and C70 fullerenes in non-aqueous capillary electrophoresis, as well as two C60 fullerene derivatives not previously reported by any electrophoretic method, N-methyl-fulleropyrrolidine (C60 pyrr) and (1,2-methanofullerene C60)-61-carboxylic acid (C60-COOH). . The separation was performed using fused-silica capillaries with an I.D. of 50 µm and tetraalkylammonium salts, namely tetra-n-decylammonium bromide (TDAB, 200 mM) and tetraethylammonium bromide (TEAB, 40 mM), in a solvent mixture containing 6% methanol and 10% acetic acid in acetonitrile:chlorobenzene (1:1 v/v) as the background electrolyte (BGE). Detection limits, based on a signal-to-noise ratio of 3:1, were calculated and values between 1 and 3.7 mg/L were obtained. Good run-to-run and day-to-day precisions on concentration were achieved with RDSs lower than 15%. For the first time, an electrophoretic technique (NACE) has been applied for the analysis of C60 fullerene in a commercial cosmetic cream. A standard addition method was used for quantitation and the result was compared with that obtained by analyzing the same cream by LC-MS

Characterisation and determination of fullerenes: a critical review

A prominent sector of nanotechnology is occupied by a class of carbon-based nanoparticles known as fullerenes. Fullerene particle size and shape impact in how easily these particles are transported into and throughout the environment and living tissues. Currently, there is a lack of adequate methodology for their size and shape characterisation, identification and quantitative detection in environmental and biological samples. The most commonly used methods for their size measurements (aggregation, size distribution, shape, etc.), the effect of sampling and sample treatment on these characteristics and the analytical methods proposed for their determination in complex matrices are discussed in this review. For the characterisation and analysis of fullerenes in real samples, different analytical techniques including microscopy, spectroscopy, flow field-flow fractionation, electrophoresis, light scattering, liquid chromatography and mass spectrometry have been reported. The existing limitations and knowledge gaps in the use of these techniques are discussed and the necessity to hyphenate complementary ones for the accurate characterisation, identification and quantitation of these nanoparticles is highlighted

Characterization of aggregates of surface modified fullerenes by asymmetrical flow field-flow fractionation with multi-angle light scattering detection

Fullerenes are carbon nanoparticles with widespread biomedical, commercial and industrial applications. Attributes such as their tendency to aggregate and aggregate size and shape impact their ability to be transported into and through the environment and living tissues. Knowledge of these properties is therefore valuable for their human and environmental risk assessment as well as to control their synthesis and manufacture. In this work, asymmetrical flow-field flow fractionation (AF4) coupled to multi-angle light scattering (MALS) was used for the first time to study the size distribution of surface modified fullerenes with both polyhydroxyl and carboxyl functional groups in aqueous solutions having different pH (6.5-11) and ionic strength values (0-200 mM) of environmental relevance. Fractionation key parameters such as flow rates, flow programming, and membrane material were optimized for the selected fullerenes. The aggregation of the compounds studied appeared to be indifferent to changes in solution pH, but was affected by changes in the ionic strength. Polyhydroxy-fullerenes were found to be present mostly as 4 nm aggregates in water without added salt, but showed more aggregation at high ionic strength, with an up to 10-fold increase in their mean hydrodynamic radii (200 mM), due to a decrease in the electrostatic repulsion between the nanoparticles. Carboxy-fullerenes showed a much stronger aggregation degree in water (50 100 nm). Their average size and recoveries decreased with the increase in the salt concentration. This behavior can be due to enhanced adsorption of the large particles to the membrane at high ionic strength, because of their higher hydrophobicity and much larger particle sizes compared to polyhydroxy-fullerenes. The method performance was evaluated by calculating the run-to-run precision of the retention time (hydrodynamic radii), and the obtained RSD values were lower than 1 %. MALS measurements showed aggregate sizes that were in good agreement with the AF4 data. A comparison of the scattering radii from the MALS with the hydrodynamic radii obtained from the retention times in AF4 indicated that the aggregate shapes are far from spherical. TEM images of the fullerenes in the dry state also showed branched and irregular clusters

Aggregation behaviour of fullerenes in aqueous solutions: a capillary electrophoresis and asymmetric flow-field flow fractionation study

In this work the electrophoretic behaviour of hydrophobic fullerenes (C60, C70 and C60-pyrr) and water soluble fullerenes (C60(OH)24, C120(OH)30, C60-pyrr tris acid and C60CHCOOH) in micellar electrokinetic capillary chromatography (MECC) was evaluated. The aggregation behavior of the water soluble compounds in MECC at different buffer and SDS concentrations and pH values of the background electrolyte (BGE) was studied by monitoring the changes observed in the electrophoretic pattern of the peaks. Broad and distorted peaks that can be attributed to fullerene aggregation were obtained in MECC which became narrower and more symmetric by working at low buffer and SDS concentrations (below the critical micelle concentration, capillary zone electrophoresis (CZE) conditions). For the characterization of the suspected aggregates formed (size and shape), asymmetrical flow field-flow fractionation (AF4) and transmission electron microscopy (TEM) were used. The results showed that the increase in the buffer concentration promoted the aggregation of the particles while the presence of SDS micelles revealed multiple peaks corresponding to particles of different aggregation degree. Furthermore, MECC has been applied for the first time for the analysis of C60 in two different cosmetic products (i.e., anti-aging serum and facial mask)

Analysis and characterisation of fullerene nanoparticles

[eng] Fullerenes or Buckyballs are a group of carbon nanoparticles, classified as engineered nanoparticles. The advent of fullerene nanoparticles in commercial, industrial and biomedical applications raises concern about their potential ecological and human health risks. Fullerenes have not been regulated, although the European Commission (European Commission, 2002), the European Parliament (European Parliament, 2008) and the US Environmental Protection Agency (EPA, 2015) have prioritised legislation on nanomaterials handling and disposal. Given the current lack of studies regarding their presence, fate and behaviour in consumer products and environmental matrices and their associated human and environmental risks it is becoming increasingly important to be able to characterise and quantitate fullerene nanoparticles, especially derivatives, in a wide range of matrix types. To fill these knowledge gaps, one of the objectives of this thesis was the development of analytical methodologies for the determination of pristine and surface modified fullerenes by ultra-high performance liquid chromatography coupled to MS (UHPLC-MS) and by nonaqueous capillary electrophoresis (NACE) and micellar electrokinetic capillary chromatography (MECC) with UV-Vis detection in different environmental matrices (water and sediment samples) and cosmetic products, respectively. In addition, in this thesis the size and shape characterisation of surface modified fullerenes in aqueous solutions of different pH and ionic strength values was studied by combining several techniques (CE, AF4-MALS and TEM). Regarding the analysis of fullerenes, the use of a sub-2 µm C18 column, toluene-methanol as a mobile phase and of APPI ionisation source allowed to develop a UHPLC method coupled to MS/(MS) for the analysis of five pristine (C60-C84) and three surface modified fullerenes (PCBM, PCBB and C60-pyrr) in less than 4.5 min showing high sensitivity and selectivity. Furthermore, the employment of H-SIM mode for pristine fullerenes (mass resolving power >12,500 FWHM), and SRM mode for fullerene derivatives, allowed achieving MLODs lower than most of those previously reported in the literature. For the extraction of the water samples, liquid-liquid extraction (LLE) with toluene and the addition of salt is proposed obtaining recoveries higher than 83 %. For sediments we propose the use of pressurised liquid extraction (PLE) performed at a high extraction temperature (150 °C) using one extraction cycle of 10 min achieving good recoveries (70-92 %). The developed methodology allowed us to report for the first time the presence of C60-pyrr, PCBM and PCBB in sediments (2.0 - 8.5 ng Kg-1 levels) and of PCBM and PCBB in pond water samples (0.1- 5.1 pg L-1 levels). Two CE methods, a non-aqueous (NACE) and a micellar (MECC) method have been developed. LOQs at mg L-1 levels were obtained with both methods making possible their application for the analysis of cosmetic products. Both methods (NACE and MECC) were applied for the quantitation of C60 in cosmetic products and the results are comparable to those obtained by LC-MS (in an anti-aging serum). With respect to the characterisation of fullerene aggregates, the use of AF4-MALS demonstrated that fullerene aqueous solutions contain particles of different aggregation degree in agreement with TEM micrographs. The size determination of the studied compounds by AF4 at different salt concentrations demonstrated that the enhanced aggregation of fullerenes with the increase in the ionic strength could explain the broad, multiple and distorted peaks obtained in MECC which were more obvious at high buffer concentration. The hydrodynamic radii of polyhydroxy-fullerenes increased more than 5 times and those of the carboxy-fullerene derivatives up to 180 nm (3rd peak) (for C60-pyrr tris acid) for 0.1M NaCl. The propensity of fullerenes to aggregate in both aqueous solutions and organic solvent mixtures justify the electrophoretic peak profiles observed in MECC (i.e., broad peaks at high electrolyte concentration) and their higher retention in C18 columns using toluene-acetonitrile compared to toluene-methanol mobile phases (due to the formation of bigger aggregates), respectively.[spa] Los fulerenos son cada vez más utilizados en medicina (administración de fármacos), en procesos ambientales (remediación) y en la industria (células solares) debido a sus propiedades estructurales y electrónicas únicas. En este contexto, es importante aumentar el conocimiento actual con respecto a las características, el comportamiento, el destino y la toxicidad de los fulerenos, una nueva clase de contaminantes emergentes orgánicos. Por lo tanto, es cada vez es más importante ser capaz de caracterizar y cuantificar las nanopartículas de fulerenos en una amplia gama de tipos de matriz y para este fin, se necesita el desarrollo de métodos analíticos para su análisis cuantitativo y cualitativo. Además de la determinación de las concentraciones de fulerenos en matrices complejas, se requiere su caracterización en términos de grado de agregación, distribución del tamaño y morfología de la superficie en soluciones acuosas de diferentes características (fuerza iónica y pH) con el fin de proporcionar herramientas para establecer su riesgo. En esta tesis se han establecido metodologías para el análisis de ocho fulerenos en muestras ambientales (agua y sedimentos) por cromatografía líquida acoplada a espectrometría de masas y se ha detectado por la primera vez la presencia de tres derivados de fulerenos. Además, se ha desarollado metodología para el análisis de fulerenos hidrofobicos y solubles en agua mediante la electroforesis capilar en medio no-acuoso (NACE) y la cromatografía capilar electrocinética micelar (MECC) y los metodos se han aplicado para la determinación de C60 en productos cosmeticos. Por último, se ha estudiado el comportamiento de agregación de los fulerenos en soluciones acuosas de diferentes características (pHs, fuerzas iónicas) mediante diferentes técnicas (electroforesis capilar (CE), asymetrical flow-field flow fractionation (AF4), microscopia electrónica de transmisión (TEM)). En este contexto se han determinado los tamaños de los agregados formados en las condiciones evaluadas, y la morfología de las partículas

Analysis of C60-fullerene fullerene derivatives and pristine fullerenes in environmental samples by ultrahigh performance liquid chromatography-atmospheric pressure photoionization-mass spectrometry

In this work, a method is proposed for the simultaneous analysis of several pristine fullerenes (C60, C70, C76, C78, and C84) and three C60-fullerene derivatives (N-methyl fulleropyrrolidine, [6,6]-Phenyl C61 butyric acid methyl ester and [6,6]-Phenyl C61 butyric acid buthyl ester) in environmental samples. The method involves the use of ultrahigh performance liquid chromatography coupled to atmospheric pressure photoionization mass spectrometry (UHPLC-APPI-MS) and allowed the chromatographic separation in less than 4.5 minutes. The product ions from tandem mass spectrometry studies of fullerene derivatives, were characterized and the most abundant one (m/z 720), corresponding to [C60]-¿, was selected for quantitation. Selected reaction monitoring (SRM at 0.7 m/z FWHM) by acquiring two transitions using both isotopic cluster ions [M]-¿ and [M+1]-¿ as precursor ions was proposed for quantitation and confirmation purposes. For pristine fullerenes, highly-selective selected ion monitoring (H-SIM) acquisition mode by monitoring the isotopic cluster ions [M]-¿ and [M+1]-¿ was used. Pressurized solvent extraction conditions were optimized in order to improve recoveries of the studied fullerene compounds from sediment samples. Values up to 87-92% for C60-fullerene derivatives and lower but still acceptable, 70-80%, for pristine fullerenes were obtained. Method limits of quantitation (MLOQs) ranging from 1.5 pg L-1to 5.5 ng L-1 in water samples and from 0.1 ng Kg-1 to 523 ng Kg-1 in sediments were obtained with good precision (relative standard deviations always lower than 13%). The applicability of the developed method was evaluated by analyzing several environmental samples such as sediments and pond water and the detected levels for C60-fullerene derivatives were of 0.1-2.7 ng Kg-1and 1.5-8.5 pg L-1, respectively. C60 and C70 were the only pristine fullerenes detected in the analyzed samples (0.1-7.2 ng Kg-1 in sediments and 9-330 pg L-1 in water pond samples)

Analysis of C60-fullerene fullerene derivatives and pristine fullerenes in environmental samples by ultrahigh performance liquid chromatography-atmospheric pressure photoionization-mass spectrometry

In this work, a method is proposed for the simultaneous analysis of several pristine fullerenes (C60, C70, C76, C78, and C84) and three C60-fullerene derivatives (N-methyl fulleropyrrolidine, [6,6]-Phenyl C61 butyric acid methyl ester and [6,6]-Phenyl C61 butyric acid buthyl ester) in environmental samples. The method involves the use of ultrahigh performance liquid chromatography coupled to atmospheric pressure photoionization mass spectrometry (UHPLC-APPI-MS) and allowed the chromatographic separation in less than 4.5 minutes. The product ions from tandem mass spectrometry studies of fullerene derivatives, were characterized and the most abundant one (m/z 720), corresponding to [C60]-¿, was selected for quantitation. Selected reaction monitoring (SRM at 0.7 m/z FWHM) by acquiring two transitions using both isotopic cluster ions [M]-¿ and [M+1]-¿ as precursor ions was proposed for quantitation and confirmation purposes. For pristine fullerenes, highly-selective selected ion monitoring (H-SIM) acquisition mode by monitoring the isotopic cluster ions [M]-¿ and [M+1]-¿ was used. Pressurized solvent extraction conditions were optimized in order to improve recoveries of the studied fullerene compounds from sediment samples. Values up to 87-92% for C60-fullerene derivatives and lower but still acceptable, 70-80%, for pristine fullerenes were obtained. Method limits of quantitation (MLOQs) ranging from 1.5 pg L-1to 5.5 ng L-1 in water samples and from 0.1 ng Kg-1 to 523 ng Kg-1 in sediments were obtained with good precision (relative standard deviations always lower than 13%). The applicability of the developed method was evaluated by analyzing several environmental samples such as sediments and pond water and the detected levels for C60-fullerene derivatives were of 0.1-2.7 ng Kg-1and 1.5-8.5 pg L-1, respectively. C60 and C70 were the only pristine fullerenes detected in the analyzed samples (0.1-7.2 ng Kg-1 in sediments and 9-330 pg L-1 in water pond samples)

Characterisation and determination of fullerenes: a critical review

A prominent sector of nanotechnology is occupied by a class of carbon-based nanoparticles known as fullerenes. Fullerene particle size and shape impact in how easily these particles are transported into and throughout the environment and living tissues. Currently, there is a lack of adequate methodology for their size and shape characterisation, identification and quantitative detection in environmental and biological samples. The most commonly used methods for their size measurements (aggregation, size distribution, shape, etc.), the effect of sampling and sample treatment on these characteristics and the analytical methods proposed for their determination in complex matrices are discussed in this review. For the characterisation and analysis of fullerenes in real samples, different analytical techniques including microscopy, spectroscopy, flow field-flow fractionation, electrophoresis, light scattering, liquid chromatography and mass spectrometry have been reported. The existing limitations and knowledge gaps in the use of these techniques are discussed and the necessity to hyphenate complementary ones for the accurate characterisation, identification and quantitation of these nanoparticles is highlighted

Field-flow fractionation for molecular-interaction studies of labile and complex systems: A critical review

Asymmetrical flow field-flow fractionation (AF4) has attracted considerable attention as a size-based separation technique, due to its mild separation conditions, broad working range (from approximately 103 to 109 Da molecular mass or from 1 nm to 1 μm particle diameter), and versatility. AF4 is primarily being used to measure particle size, polydispersity, and physical stability of various systems, such as (bio)-macromolecules and nanoparticles. In comparison with size-exclusion chromatography (packed column), AF4 (open channel) allows separation while preserving labile structures. Monitoring of interactions between different compounds and in very complex matrices is possible. Preservation of the structure and correlation of structural characteristics with activity and functionality can bolster the development of new therapeutic strategies for diseases and new materials with improved properties. In this review, a detailed overview is presented of developments in AF4 for interaction studies between various systems, such as protein-protein, polymer-polymer, nanoparticle-drug, and nanoparticle-protein. The prospects and obstacles for AF4, and other less-commonly used types of FFF, for studying interactions within complex and fragile systems are covered. Coupling AF4 to a variety of detection systems can greatly contribute to the understanding of the interaction/association processes and provide information on the interaction kinetics. This review is intended to provide comprehensive documentation on the types of information (structural, morphological, chemical) on molecular interactions that can be retrieved by AF4