Carmen Cámara

Nanoparticles: a global vision. Characterization, separation, and quantification methods. Potential environmental and health impact

Nanotechnology is a multidisciplinary science that includes scientific and technological activities at molecular and atomic scales (1–100 nm). Scientific principles and new properties can be understood and controlled when working at this scale. Nanotechnology is advancing rapidly due to the great progress achieved in various fields including electronics, mechanics, medicine, cosmetics, food, etc. This increased use of nano-sized materials leads to the release of a substantial amount of nanoparticles into the environment. To date there is a lack of standardized procedures to assess their safety and impact on the environment. Specific toxicological studies as well as characterization and quantification of nanoparticles are required to establish regulations to control field application of nanoscale materials. A classification of nanoparticles and the techniques employed in their characterization, separation, and quantification are summarized and described in this review. A global perspective on nanoparticle exposure and environmental effect is also discussed.

Analytical techniques applied to the speciation of selenium in environmental matrices

Abstract The toxicity and essential nature of Se in the environment depend on its concentration and the chemical forms in which it is present. Se and its derivatives may be widely dispersed throughout the environment as a result of anthropogenic inputs such as fossil fuel combustion and industrial, agricultural and natural processes. In order to evaluate the effects of the different Se species on living organisms, sensitive analytical methods are required for their determination in complex environmental matrices. An overview is given of the importance of Se speciation and the distribution, accumulation and transformation of the species in the environment. The state of the art of various techniques is discussed. The main sources of errors in each step involved in the analytical methods are reported and the importance of quality control and the need to use reference materials are also stressed.

Mycobacteria release active membrane vesicles that modulate immune responses in a TLR2-dependent manner in mice

Bacteria naturally release membrane vesicles (MVs) under a variety of growth environments. Their production is associated with virulence due to their capacity to concentrate toxins and immunomodulatory molecules. In this report, we show that the 2 medically important species of mycobacteria, Mycobacterium tuberculosis and Mycobacterium bovis bacille Calmette-Guérin, release MVs when growing in both liquid culture and within murine phagocytic cells in vitro and in vivo. We documented MV production in a variety of virulent and nonvirulent mycobacterial species, indicating that release of MVs is a property conserved among mycobacterial species. Extensive proteomic analysis revealed that only MVs from the virulent strains contained TLR2 lipoprotein agonists. The interaction of MVs with macrophages isolated from mice stimulated the release of cytokines and chemokines in a TLR2-dependent fashion, and infusion of MVs into mouse lungs elicited a florid inflammatory response in WT but not TLR2-deficient mice. When MVs were administered to mice before M. tuberculosis pulmonary infection, an accelerated local inflammatory response with increased bacterial replication was seen in the lungs and spleens. Our results provide strong evidence that actively released mycobacterial vesicles are a delivery mechanism for immunologically active molecules that contribute to mycobacterial virulence. These findings may open up new horizons for understanding the pathogenesis of tuberculosis and developing vaccines.

Solid-phase microextraction method for the determination of atrazine and four organophosphorus pesticides in soil samples by gas chromatography

A simple and rapid solid-phase microextraction (SPME) based method is presented for the simultaneous determination of atrazine and four organophosphorus (i.e. parathion-methyl, chlorpyriphos, methidathion and carbophenothion) in soils. After optimisation of the different experimental variables affecting the SPME of the target compounds from aqueous solutions by using an experimental design, a consensus strategy was adopted which allowed the use of the SPME method developed for the simultaneous screening of all the analytes selected. The complete analytical procedure finally proposed consisted of a 15-min ultrasonic extraction of the target compounds from a 0.5-g soil sample with 5 ml of methanol and the dilution of this extract to up 10% methanol followed by the addition of NaCl to a final concentration of 10% (w/v). The analytes in this aqueous extract were preconcentrated for 30 min in the SPME fiber and subsequently desorbed by heating of the fiber at 260 degrees C for 5 min in the gas chromatograph injection port. Final determination was carried out with an electron-capture detector. The recoveries of the pesticides studied in soils ranged from 72 to 123%, except for atrazine, and the SDs were below 16%. The feasibility of the procedure finally proposed for the screening of the endogenous pesticides irrespective of the properties of the soil selected has been shown.

Biological substrates for metal preconcentration and speciation

Abstract This article summarizes the state of the art of metal preconcentration and speciation using biological organisms such as algae, plant-derived materials, bacteria, yeast, fungi and erythrocytes. Although biosorption has been the subject of increasing research for a variety of reasons, including its potential application in the recovery of metals from manufacturing processes, the treatment of contaminated water and the recovery of precious metals in mining operations, only recently has it been exploited for analytical measurement. Basic techniques and principles are discussed and recent developments reviewed. Special attention is given to immobilization procedures and some biosorption mechanisms are considered.

Evaluation of selective uptake of selenium (Se(IV) and Se(VI)) and antimony (Sb(III) and Sb(V)) species by baker's yeast cells (Saccharomyces cerevisiae)

Abstract Common bakers yeast cells characterized as Saccharomyces cerevisiae were evaluated as a means of sequestering Se and Sb in different oxidation states (Se(IV), Se(VI), Sb(III) and Sb(V)) from aqueous solution. Several parameters affecting the degree of bioaccumulation of these elements were studied — solution pH, temperature, incubation time, and amount of biomass and analyte. The results obtained show that the biosorption process and its mechanism depend not only on the element but also on its oxidation state. In presence of yeast, aqueous Se(VI) remained unaltered and in solution under all the experimental conditions tested while Se(IV) is accumulated into the cell. The degree of accumulation depends on the amount of yeast, incubation time and temperature. Se(IV) is quantitatively bound to the yeast under the optimum conditions, i.e. 700 mg bakers yeast, 30 min incubation time at pH 7.0 and 37 °C. The accumulation step may occur along with transformation processes of Se(IV), probably a reduction to Se(-II) species. Sb(III) was completely bound to the yeast cells at an incubation temperature of 60°C at pH 7, whereas Sb(V) showed less affinity and was unaffected under these conditions. The proposed method allows the specific sampling of Se and Sb species, which is especially important in environmental analysis since Sb(III) and Se(IV) are more toxic than Sb(V) and Se(VI), respectively.

On line speciation of Se(VI), Se(IV), and trimethylselenium by HPLC-microwave oven-hydride generation-atomic absorption spectrometry

An on-line system is proposed consisting of an anion-exchange chromatographic column, microwave-induced thermooxidation of trimethylselenium in the presence of persulphate, and microwave-induced thermoreduction of Se(VI) to Se(IV) in HCl medium, followed by hydride generation and atomic absorption for the determination of trimethylselenium (TMeSe), Se(IV) and Se(VI). Trimethylselenium is eluted in the dead volume of an anion-exchange column (Hamilton PRP-X-100), before elution of Se(IV) and Se(VI). Optimum chromatographic conditions have been obtained using 100 mmol L−1 phosphate buffer (pH=6.8) H2PO4−/HPO42−as the mobile phase. Recoveries were around 100%, absolute detection limits were 1.1, 1.4 and 2.2 ng for TMeSe, Se(IV) and Se(VI), respectively. Precision was lower than 10% in all cases. The method has been applied to tap water.

Separation and determination of antimony(III) and antimony(V) species by high-performance liquid chromatography with hydride generation atomic absorption spectrometric and inductively coupled plasma mass spectrometric detection

Methods are described for the effective separation and determination of inorganic antimony species by high-performance liquid chromatography (HPLC)–hydride generation (HG) atomic absorption spectrometry (AAS), HPLC–inductively coupled plasma (ICP) mass spectrometry (MS) and HPLC–HG–ICP-MS. SbIII and SbV were separated on a strong anion-exchange column using phthalic acid as the mobile phase. The optimum conditions for the separation of the antimony species by HPLC and the hydride generation conditions for the determination by AAS were established. Then, the HPLC system was connected to an ICP-MS system using either nebulization or hydride generation sample introduction to improve the detection limits. The detection limits were 5 and 0.6 ng per 100 µl sample for SbIII and SbV, respectively (HPLC–HGAAS). For the HPLC–ICP-MS determination these limits were 0.75 and 0.09 ng and 0.04 and 0.008 ng for the HPLC–HG-ICP-MS coupling. The proposed methods for the simultaneous separation of inorganic antimony species were applied to the determination of SbIII and SbV in spiked and natural water samples. Agreement within the statistical uncertainty was obtained in all instances.

Quantification and speciation of mercury and selenium in fish samples of high consumption in Spain and Portugal.

Mercury (Hg) and selenium (Se) determinations were carried out to evaluate human exposure to those elements through fish consumption in Spain and Portugal. Atomic fluorescence spectroscopy (AFS) was applied in a cold vapor mode for total mercury quantification and was also hyphenated to gas chromatography (GC) to achieve the speciation of organomercurial species in fish samples. The results obtained show the highest concentration of Hg in swordfish and tuna (0.47±0.02 and 0.31±0.01 μg g−1, respectively), and a much lower concentration in sardine, mackerel shad, and octopus (0.048±0.002, 0.033±0.001, and 0.024±0.001 μg g−1, respectively), The determination of alkyl mercury compounds revealed that 93–98% of mercury in the fish samples was in the organic form. Methylmercury (MeHg) was the only species found in the three fish species with higher mercury content.Total selenium concentraton was high in sardine, swordfish, and tuna (0.43±0.02, 0.47±0.02, and 0.92±0.01 μg g−1, respectively), but low in mackeral shad and octopus (0.26±0.01 and 0.13±0.01 μg g−1, respectively). Speciation of selenium compounds was done by high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry (LC-ICP-MS). Selenomethionine (SeMet) was the only selenium compound identified in the fish samples with higher selenium content.Among the fish species studied, sardine had the most favourable Se:Hg and SeMet:MeHg molar ratios; therefore, its consumption seems to be preferable.

Migration and characterisation of nanosilver from food containers by AF4-ICP-MS

In this work, silver migration from commercial food containers was evaluated according to European Regulation 10/2011. Several experimental parameters affected silver release: food simulant, temperature, exposition time and sampled bag area. Results demonstrated a significant silver nanoparticle (AgNP) migration into aqueous and acidic simulants. The amount of silver migrated increased with storage time and temperature although, in general, silver showed a low tendency to migrate into food simulants (17 ng/g). However, the food simulant did not seem to be a really outstanding variable for long term storage. AF(4)-ICP MS was used to confirm the presence of AgNPs in the simulants. The low limit of detection achieved (0.4 μg L(-1)) allowed the identification of AgNPs and their size characterisation (40-60 nm). Finally, scanning electron microscopy/energy-dispersive X-ray analysis suggested a possible transformation of the AgNPs detected in the extracts, due to association with other ligands, such as chlorine and sulphur, present in the original containers.