martes, 4 de octubre de 2016

Antimony speciation in soils, sediments and volcanic ashes by microwave extraction and HPLC-HG-AFS detection

On the 5th of May 2008, the first recorded eruption of the Chaitén Volcano in southern Chile occurred. Because one of the main natural sources of Sb is volcanic activity, it was necessary to study the distribution of Sb and its species in the nearby ecosystem. The present study aims to develop a methodology for total Sb determination by ICP-MS and a method for Sb(V) and Sb(III) determination by HPLC-HG-AFS in soils, sediments and volcanic ash.
Chaiten eruption, Xinhua Photo
Microwave digestion in a 6 mL HNO3 and 0.5 mL HBF4 acid digestion mixture can achieve total solubilization of Sb in solid samples. Thirty minutes at 200 °C with 100 mmol L− 1 of oxalic acid were suitable conditions for fast and efficient microwave extraction to obtain a good extraction yield. However, Sb(III) stabilization was strongly inhibited; thus, the mixture of 100 mmol L− 1 + 20 mmol L− 1 of ascorbic acid was the best for Sb solubilization and Sb(III) stabilization. A total of 1.8 ± 0.1 μg g− 1 of Sb was quantified in the volcanic ash from the first eruption. The Sb concentrations in the sediments were 3 times higher than the Sb concentrations in the sediments from the reference zone. In the extracts of the volcanic ash and sediment, Sb(III) was the most abundant species, accounting for 70 to 97% of the total Sb found in the extracts. The results suggest that most of the Sb thrown from the Chaitén Volcano accumulated in the sediments at the mouths of the Yelcho and Chaitén Rivers, mainly in the form of Sb(III). Read more

martes, 5 de julio de 2016

A semiautomatic system for soluble lead and copper monitoring in atmospheric deposition by coupling of passive elemental fractionation sampling and voltammetric measurement on screen printed gold electrodes

We propose here the concept of semiautomatic measurement of soluble copper and lead in atmospheric deposition by the coupling of filtrating-bulk passive sampling by an atmospheric elemental fractionation sampler (AEFS) designed for fractionation of soluble and insoluble elemental species, and square wave anodic stripping voltammetric detection on screen printed electrodes. The voltammetric parameters were optimized to provide a reliable method for Pb(II) and Cu(II)monitoring with detection limits in the low ng mL−1 range. The method was validated
by analyzing ambient water certified referencematerials with good agreement between measured and certified values. The monitoring system was tested during a 1 month experimental campaign in a suburban area and proved useful to monitor copper changes in the atmospheric deposition. Leadwas alsomeasurable after fortification since its levels were under the detection limit of the voltammetric method. The results obtained were contrasted by a lab based standard ICP-MS method with good correlation.Our results are promising about the possibility of routine field use of unattended
voltammetric measurements of trace element monitoring in atmospheric deposition. Published in Microchemical Journal, 2016. Read more

martes, 21 de junio de 2016

Temporal and spatial variation of trace elements in atmospheric deposition around the industrial area of Puchuncaví-Ventanas (Chile) and its influence on exceedances of lead and cadmium critical loads in soils

Fractionation of elemental contents in atmospheric samples is useful to evaluate pollution levels for risk assessment and pollution sources assignment. We present here the main results of long-term characterization of atmospheric deposition by using a recently developed atmospheric elemental fractionation sampler (AEFS) for major and trace elements monitoring around an important industrial complex located in Puchuncaví region (Chile). Atmospheric deposition samples were collected during two sampling campaigns (2010 and 2011) at four sampling locations: La Greda (LG), Los Maitenes (LM), Puchuncaví (PU) and Valle Alegre (VA). Sample digestion and ICP-MS gave elements deposition values (Al, As, Ba, Cd, Co, Cu, Fe, K, Mn, Pb, Sb, Ti, V and Zn) in the insoluble fraction of the total atmospheric deposition. Results showed that LG location, the closest location to the industrial complex, was the more polluted sampling site having the highest values for the analyzed elements. PU and LM were the next more polluted and, finally, the lowest elements concentrations were registered at VA. The application of Principal Component Analysis and Cluster Analysis identified industrial, traffic and mineral-crustal factors. We found critical loads exceedances for Pb at all sampling locations in the area affected by the industrial emissions, more significant in LG close to the industrial complex, with a trend to decrease in 2011, whereas no exceedances due to atmospheric deposition were detected for Cd. Paper published in Chemosphere. Read more

martes, 31 de mayo de 2016

Long-term assessment of ecological risk from deposition of elemental pollutants in the vicinity of the industrial area of Puchuncaví-Ventanas, central Chile

The present work investigates soil pollution by elemental contaminants and compares ecological risk indexes related to industrial activities for the case study of Puchuncaví-Ventanas: a relevant industrial zone located in central Chile. Selected elements (As, Pb, Cd, Ni, Hg, V, Mn, Zn, Sr, Sb, Cr, Co, Cu, K, and Ba) were analyzed during a long-term period (yearly sampling campaigns during 2007–2011), at 5 sampling stations representing different degrees of impact. PCA and cluster analysis allowed identifying a copper smelter and a coal-fired power plant complex asmajor pollution sources. Geoaccumulation index (Igeo), enrichment factor (EF), contamination factor (Cf), contamination degree (Cdeg), and integrated pollution index (IPI) are critically discussed for quantitative ecological risk assessment. Igeo, EFandCf indexes are producing comparable environmental information, showing moderate to high pollution risks in the area that demands furthermonitoring and adoption of prevention and remediation measures. Published in Science of the Total Environment. Read more

martes, 17 de mayo de 2016

Ambient air levels and health risk assessment of benzo(a)pyrene in atmospheric particulate matter samples from low polluted areas: application of an optimized microwave extraction and HPLC-FL methodology

A new methodology involving a simple and fast pretreatment of the samples by microwave-assisted extraction and concentration by N2 stream, followed by HPLC with fluorescence detection, was used for determining the concentration of benzo(a)pyrene (BaP) in atmospheric particulate matter (PM10 fraction). Obtained LOD, 1.0 × 10−3 ng/m3, was adequate for the analysis of benzo(a)pyrene in the samples, and BaP recovery from PAH in Fine Dust (PM10-like) certified reference material was nearly quantitative (86 %). The validated procedure was applied for analyzing 115 PM10 samples collected at different sampling locations in the low-polluted area of Extremadura (Southwest Spain) during a monitoring campaign carried out in 2011–2012. BaP spatial variations and seasonal variability were investigated as well as the influence of meteorological conditions and different air pollutants concentrations. A normalized protocol for health risk assessment was applied to estimate lifetime cancer risk due to BaP inhalation in the sampling areas, finding that around eight inhabitants per million people may develop lung cancer due to the exposition to BaP in atmospheric particulates emitted by the investigated sources. Published in Environmental Science and Pollution Research. Read more

jueves, 28 de abril de 2016

Mercury pollution assessment in soils affected by industrial emissions using miniaturized ultrasonic probe extraction and ICP-MS

A combination of probe ultrasonic extraction, optimized by surface response methodology, and Inductively coupled plasma mass spectrometry (ICP-MS) detection is described in this work as an effective methodology  for mercury monitoring in soils affected by industrial emissions. Minute amounts of samples (typically
20 mg) can be extracted in 3 min by 1 mL of HCl-based extracting solution, without risk of mercury losses, and sub sequentially assayed by ICP-MS. The method was successfully tested on soil standard reference materials and then applied to mercury monitoring in a large set of real soil samples collected during a long-term monitoring survey (2007–2011) around the industrial area of Puchuncaví, Chile. The method proved to be useful for investigation of spatial and temporal mercury variability in the area, showing an intermediate to high mercury contamination with potential impact on the surrounding ecosystem. Published in the International Journal of Environmental Science and Technology.  Read more

miércoles, 23 de marzo de 2016

Wearable electrochemical sensors: innovative tools for the emerging mobile health ecosystem

Wearable electrochemical sensors: innovative tools for the emerging mobile health ecosystemJournal of Applied Bioanalysis 1(3) (2015) 68-71. With an estimated present global market of US$ 86.3 billion and expected annual increase around 7.9 % from now to 2020, sensors are nowadays one of the most active areas of research and technological developments [1] and a basic pillar of the emerging mobile health strategy that is expected to be revolutionizing healthcare in the near future. The biosensor and chemical sensor category is one of the most growing segment of this market, mainly due to increased use for medical purposes. Wearable electrochemical sensors conform a particularly flourishing category that benefits from the improvements in micro and nano fabrication of electrodes and instrumental components based on a range of new electrode materials (e.g. graphene). They are also expanding thanks to the widespread availability of advanced signal processing and management technologies on smartphones, tablets and similar portable devices. The aim of this contribution is to highlight the most outstanding recent progresses in the field of wearable electrochemical sensors for decentralized bioanalysis and show some examples of research trends that will shape the sector and expand applicability fields in the near future.