Improving the detectability of microplastics in river waters by single particle inductively coupled plasma mass spectrometry

Detection of microplastics in environmental samples requires fast, sensitive and selective analytical techniques, both in terms of the size of the microparticles and their concentration. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) allows the detection of plastic particles down to ca. 1 µm and down to concentrations of 100 particles per mL. In SP-ICP-MS, detection of carbon-containing particles is hampered by the presence of other forms of carbon (carbonates, organic matter, microorganisms…). An acidic pre-treatment of river water samples with 10% (v/v) nitric acid for 24 h allowed the reduction of the presence of dissolved carbon to ultrapure water levels and the digestion of potential microorganisms in the samples, recovering polystyrene microparticles up to 80%. Carbon-containing particles were detected in most of the samples analysed from Spanish and French Pyrenean rivers. The presence of microplastics in these samples was confirmed by Raman microscopy and their morphology was defined by electron microscopy combined with energy-dispersive X-ray spectroscopy. The developed SP-ICP-MS method is suitable for the rapid screening of river waters for the presence of microplastics, which can then be analysed by inherently slower but more selective techniques (e.g., Raman microscopy)

ICTs, ESPs and ZPD through microlessons in teacher education

This paper presents the initial results of the use of dialogic interaction enhanced by the use of technology in teaching English in different settings and subjects of teacher education. Technology is used in three different ways: as a support (video) for analysis through teacher-instructor interaction, as a means of social interaction and use of language for education between teacher and students (use of the computer for instruction), and as the creation of own designed materials for language training (through the use of technology). Data is obtained from video-recordings related to teaching and learning English as a foreign language by three different teachers in three subjects from Primary and Infant Education at Universidad de Alcalá. Results indicate that microteaching is not only valid as a training method but also to introduce new content and concepts that have not been previously introduced in the classes. The interaction in the Zone of Proximal Development (ZPD) between the teacher-instructor and the teacher-students also proves to have a powerful effect in motivation, teaching improvement and language for education skills development through self-reflection

Catching particles by atomic spectrometry: Benefits and limitations of single particle - inductively coupled plasma mass spectrometry

Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) has led ICP-MS into a new dimension, turning an ensemble technique for elemental and isotope ratio analysis into a particle counting technique and well beyond. SP-ICP-MS allows the detection of particles, their size characterization and the quantification of their number and mass concentrations, as well as the dissolved forms of the target element(s). Although the technique is mostly applied to metal- and metalloid-based nanoparticles, its application to microparticles and carbon-based particles are emerging. After twenty years since the first publications and more than ten years of ongoing development, SP-ICP-MS has reached a high degree of maturity, with an increasing number of applications in a wide range of fields. Despite this trend, there are aspects related to the fundamentals of the technique that still require further studies. This review is organized around the fundamentals of the technique along with the different steps and processes involved, from the sample introduction to the signal processing, offering an updated view of these topics, focusing on the benefits and current limitations of the technique, as well as its future perspectives

An ICP-MS-based platform for release studies on silver-based nanomaterials

Engineered nanoparticles are being incorporated into different products and nanocomposites. The release of these nanoparticles, as well as other derived species, can subsequently lead to consumer and environmental exposure, being a relevant factor for risk assessment. The need for analytical methods for the detection, characterization and quantitation of these released species under relevant conditions becomes evident. In this work, a platform of methods based on the use of inductively coupled plasma mass spectrometry (ICP-MS) is proposed to obtain information about the release of silver from silver based nanocoatings and nanocomposites. The sensitivity and element specific response of conventional ICP-MS is complemented by the use of the technique in single particle mode and in combination with ultrafiltration and asymmetrical flow field flow fractionation. By using these three methods, information about the release of both dissolved and particulate forms of silver, as well as the size of the nanoparticles, can be obtained under a variety of scenarios at concentrations down to 0.1 µg L-1 and a nanoparticle diameter of 5 nm. The feasibility of the platform was checked through a number of paradigmatic cases

About detectability and limits of detection in single particle inductively coupled plasma mass spectrometry

Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) offers unique features for the detection of particles, as well as for their quantification and size characterization. The detection capabilities of SP-ICP-MS are therefore not only limited to the concentration domains (of particles and dissolved related species), but also to the mass of element per particle and particle size domains. Discrimination and detection of particle events, based on the use of robust limits of decision (also known as critical values), and the estimation of the limits of detection in the different domains, require standardized metrological approaches that have not been clearly established yet. As a consequence, harmonized approaches and expressions to allow reliable comparisons between methods and instruments, as well as to process SP-ICP-MS data, are required. This paper is an attempt to summarize and review the different approaches applied up to now in relation to the detectability in SP-ICP-MS, and highlight the peculiarities of this topic in SP-ICP-MS. A holistic approach with criteria and expressions for the estimation of the different critical values and limits of detection in terms of the different instrumental and experimental parameters involved is proposed. Additionally, a calculation tool for estimating and predicting critical values and limits of detection under different experimental conditions is also included

Anatomy of corpus callosum in prenatally malnourished rats

Indexación: Web of Science; ScieloThe effect of prenatal malnutrition on the anatomy of the corpus callosum was assessed in adult rats (45-52 days old). In the prenatally malnourished animals we observed a significant reduction of the corpus callosum total area, partial areas, and perimeter, as compared with normal animals. In addition, the splenium of corpus callosum (posterior fifth) showed a significant decrease of fiber diameters in the myelinated fibers without changing density. There was also a significant decrease in diameter and a significant increase in density of unmyelinated fibers. Measurements of perimeter's fractal dimensions from sagittal sections of the brain and corpus callosum did not show significant differences between malnourished and control animals. These findings indicate that cortico-cortical connections are vulnerable to the prenatal malnutrition, and suggest this may affect interhemispheric conduction velocity, particulary in visual connections (splenium).http://ref.scielo.org/nph4s

Detection, quantification, and characterization of polystyrene microplastics and adsorbed bisphenol A contaminant using electroanalytical techniques

The potential applications of electroanalytical techniques for the quantification and size characterization of nonelectroactive polystyrene microplastics is reported, in addition to characterizing the kinetics of adsorption of bisphenol A on these polystyrene microparticles. The individual adsorption events of very diluted polystyrene microparticles dispersions on glassy-carbon microelectrodes produce the blocking of the charge transfer of a mediator (ferrocene-methanol) thus decreasing the current of the recorded chronoamperogram in a stepwise manner. The magnitude of the current steps are in the order of pA values and can be related to the diameter of the plastic microparticles in the size range 0.1 to 10 µm. The frequency of the current steps in the domain time used (120 s) allows to quantify the number concentration of these microparticles in the range 0.005 to 0.500 pM. Electrochemical impedance spectroscopy confirms the adsorption of the polystyrene microplastics on carbon microelectrodes (and to a lesser extent on platinum microelectrodes) under the same experimental conditions as above. On the other hand, the adsorbed microplastics become concentrators of other pollutants found in the environment. The sensitive differential-pulse voltammetry determination of bisphenol A (linear range 0.80–15.00 µM; detection limit 0.24 µM) was used together with a simple separation procedure for studying the adsorption of bisphenol A on polystyrene microparticles. The adsorption capacity (mg of bisphenol A retained per g of the polystyrene microplastics) decreased from approximately 5.7 to 0.8 mg g−1 with increasing dosages of polystyrene microparticles from 0.2 to 1.6 g l−1. The adsorption isotherms were modeled resulting in a monolayer of bisphenol A adsorbed on the microplastics (i.e., best fitted to a Langmuir model)

Contribution to optimization and standardization of antibacterial assays with silver nanoparticles: the culture medium and their aggregation

The antimicrobial activity of silver nanoparticles is determined by their size and specific properties, as well as by the chemical composition of the exposure medium in which the nanoparticles are suspended. When the antibacterial tests are carried out in a culture medium, aggregation of the nanoparticles is produced, decreasing their effectiveness. This study proposes the addition of surfactants to the culture medium to prevent the aggregation of silver nanoparticles and optimizes the concentrations of these surfactants. The aggregation of silver nanoparticles was studied by dynamic light scattering (DLS) after dispersion in three liquid culture media (Mueller-Hinton (MH), Luria-Bertani (LB) and Brain Heart Infusion) in which four different surfactants (SDS, Triton X100, Tween 80 and CTAB) were added at concentrations of 0, 0.1, 0.5, 1, 1.5 and 2%. Results showed that, the optimal culture media to prevent aggregation of silver nanoparticles were MH and LB with higher concentrations of Tween 80 and Triton X100 surfactants; being MH + 2% of Tween 80 and MH + 1% Triton X100 the best combinations obtained because the results obtained were closest to the sizes of nanoparticles in ultrapure water. In addition, it has been verified that the optimal medium + surfactant combinations chosen did not affect the viability of Escherichia coli bacteria. Nanoparticle aggregation was not observed by single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) when nanoparticles were incubated for long incubations periods (24 h) in the optimal medium chosen

Analysis of Circadian Stimulus and Visual Comfort Provided by Window Design in Architecture

Light is the major synchronizer of circadian rhythms to the 24-hour solar day. Compared to the visual system, the circadian system requires more light to be activated and is more sensitive to short-wavelength light. Daylighting is an ideal light source for circadian entrainment. Architectural and design features, such as window size and room reflectances impact the amount of circadian stimulus that the patient will receive. DaySim 3.2 simulations were used to determine the percentage of days that occupants would receive a minimum circadian stimulation of 0.50 for at least an hour during the morning. According to a phototransduction model of the human circadian system, a circadian stimulation of 0.50 is equivalent to suppressing the hormone melatonin by about 50%. This circadian stimulus criterion is examined for different window to wall ratios, for two average room reflectances, and for four latitudes. The present paper provides an example of a tool that could be used to assist designers in fenestration and interior design

Elogio conque la nacion española felicita a su monarca ... Carlos IV, en su glorisisima exaltacion al trono

Fecha : "1789" tomada del Palau, T. III nº 43398.Pie de imp. tomado de colofón.Sign. : [] 2, *