Quantification Of Metals Research Articles

Total polyphenol content and metals determination in Spanish virgin olive oils by means of a dispersive liquid-liquid aerosol phase extraction method and ICP-MS

This report presents a study on the determination of total polyphenols together with metals in several samples of olive oil produced in Spain. The results provided by applying a conventional extraction method were compared against those encountered by means of the so-called Dispersive Liquid-Liquid Aerosol Phase Extraction method. The novel method is based on the dispersion of the extracting solution in the sample. To accomplish this, an aerosol is pneumatically generated and directed against the surface of the oil sample. The aerosol was generated in order to increase as much as possible the surface area of the interface between the two involved non-miscible phases. As a result, the partition equilibrium was quickly achieved. The critical variables dictating the characteristics of the obtained aerosols as well as those influencing the partition equilibrium state were studied. With the aerosol phase extraction method, the values corresponding to the total polyphenols and metals in real samples were not statistically different as compared to those obtained by the conventional liquid – liquid extraction method. The new method provided shorter extraction times and lower mass of consumed reagents than the conventional one, thus giving rise to a more environmentally friendly method. For polyphenols, calculated limits of detection and quantification were 0.48 and 1.5 mg of gallic acid kg−1, respectively. The absorbance linearity, in turn, was kept from 0 to 50 mg kg−1 (R2 = 0.998). In the case of metal and metalloid quantification, the limits of detection found with a sample digestion method ranged from 1.3 (Cu) to 291 (Na) ng mL−1. Meanwhile, because of the lower dilution factor, this parameter was one order of magnitude lower when these elements were extracted according to the new method. The new extraction method was applied to the analysis of 42 extra virgin olive oils both bottled and directly collected from the oil press, containing single cultivars or blends and produced from different areas. Fresh oils were analyzed and a preliminary study on the oil thermal degradation was also done. Dispersing the extracting solution as an aerosol into the sample can be considered a versatile method able to provide extensive oil chemical information in a rapid way what is especially important in the case of polyphenols.

A review: Analytical methods for heavy metals determination in environment and human samples

Heavy metals are vital and necessary in our daily lives. Moreover, if the amounts of heavy metals are more than the acceptable amounts (mentioned by WHO) in soil, water, and air, indeed, they cause a lot of diseases in human bodies. Therefore, monitoring and measuring the amounts of heavy metals that are arduous and difficult are so important. In this review paper, a lot of studies that have been carried out on the determination and quantification of heavy metals in human bodies, soil, and water are considered. Moreover, the effect of toxicity of each heavy metal on human health is assessed. According to WHO, EPA, NIOSH, ACGIH, and clinical chemistry, the determination of heavy metals such as Cd, Pb, Zn, Hg, Cu, Mn is very important in the human body and Environmental matrixes.

Fuzzy synthetic evaluation and health risk assessment quantification of heavy metals in Zhangye agricultural soil from the perspective of sources

Heavy metals in agricultural soil receive much attention because they are easily absorbed by crop into the ecosystem. Managing the discharge of heavy metals from the source is an effective way to prevent and control heavy metals pollution. Grouped principal component analysis (GPCA) and Positive Matrix Factorization (PMF) receptor models were utilized in this study to conduct source apportionment, and the former was optimal because of the accuracy of predicting. Based on the source contribution by GPCA/APCS, heavy metals were evaluated by fuzzy synthetic evaluation model and health risk assessment model. The results of source apportionment showed that heavy metals in Zhangye agricultural soil were mainly affected by steel industry, traffic, agrochemicals, manures, mining activities, leather industry and metal processing industry source. Fuzzy synthetic evaluation showed that the pollution levels of Chromium (Cr) derived by leather industry and metal processing industry and Nickel (Ni) derived by steel industry and traffic source were higher. Health risk assessment revealed that the non-carcinogenic and carcinogenic risks of Cr derived by leather industry and metal processing industry and Lead (Pb) derived by steel industry and traffic source were higher.

Development and Validation of a Sector-Field Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) Method for Analyzing the Diagenesis-Designating Metals in Marine Sediments

The inductively coupled plasma – mass spectrometry (ICP-MS) technique was applied for the quantification of specific metals in marine sediments following a four-step microwave-assisted digestion protocol. The effects of microwave heating and digesting medium on metal recovery were investigated using lake and river sediment reference materials to minimize the deviations from certified values. Increasing the temperature and time variables improves the accuracy of the ICP-MS measurements so that an optimized acid-digestion protocol enables the determination of heavy metals in sediments with relative errors better than 10%. The developed method was applied to measure longitudinal metal distribution in sediments collected from the continental shelf of the East Siberian Sea in the range from 50 to 600 km. Minima in the content of redox sensitive elements such as Mn, Mo, V, U, and Sb at distances from 200 to 300 m to the coast are most likely related to diagenetic processes such as sulfide reduction in the upper part of the sediment. In addition, the quality of sediments under consideration was assessed in terms of the average and maximum concentrations of heavy metals that may contaminate the bottom seawater. The developed method can be recommended as a standard tool for accurate and precise sediment analysis with important geochemical and environmental implications.

Potential metal-binding ability of proteins in the extracellular slime of Laccaria bicolor exposed to excessive Cu and Cd.

Ectomycorrhizal fungi can enhance the tolerance of plants to heavy metal stress by reducing the accumulation of heavy metals in the aerial parts of the plants. Extracellular chelation is a major mechanism of heavy metal tolerance in ectomycorrhizal fungi in which extracellular slime plays a fundamental role. The objectives of this study were to investigate the potential metal-binding ability and the protein composition of extracellular slime. The extracellular slime of Laccaria bicolor (L. bicolor) cultivated under Cd2+ and Cu2+ stress was separated using various ultrasonic pre-treatments. The protein content, composition, and metal content of the extracellular slime were measured. The results showed that the protein content in the extracellular slime significantly increased under both Cd2+ and Cu2+ stress. The SDS-PAGE profile showed that Cd2+ and Cu2+ stress induced the expression of several new proteins. Heavy metal quantification revealed that the Cd content fixed in the extracellular slime accounted for 22-28% of the metal fixed by the fungal mycelia. Meanwhile, no Cu was detected in the fungal extracellular slime, implying that the extracellular slime may not be effective for the fixation of essential metallic elements such as Cu. Taken together, these results provided evidence that L. bicolor was able to ameliorate the intracellular Cd content by stimulating extracellular slime exudation and altering the composition of the proteins therein. Nevertheless, this blocking strategy may be effective only for the non-essential element Cd and was ineffective for the physiological element Cu.

Application of gold nanoparticles embedded in the amyloids fibrils as enhancers in the laser induced breakdown spectroscopy for the metal quantification in microdroplets

In this work Nanoparticle Enhanced Laser Induced Breakdown Spectroscopy (NELIBS) has been employed for quantitative metal detection using amyloid fibrils coated with gold nanoparticles as enhancers. Amyloid fibrils represent, from one hand, an extremely interesting system for novel technologies, ranging from water purification to medical applications, and on the other hand, an ideal system for investigating the performance of laser-matter interaction in biological systems. The results obtained in this work show the potentiality of NELIBS for the quantification at sub-ppm (mg/kg) level of metallic elements (Cr, Pb, Tl and Cd) even in the protein and/or biological environment, employing amyloid fibrils with gold nanoparticles. Moreover, the single-shot measurements reveal the promising use of this technique in applications where high sensitivity and/or limitation in the sample amount are demanded.

Quantification of the diagenesis-designating metals in sediments by ICP-MS: Comparison of different sample preparation methods

Concentrations of specific metals in sediments are of immense importance in geochemical studies related to diagenetic processes, and quantification can be most reliably performed by ICP-MS after bringing the sample into solution. It is the latter analytical operation that generates a discord as no common sample preparation approach has been yet accepted. To resolve this challenge, we compared different modes of acidic sample digestion (in open and closed systems, applying in the latter case conventional or microwave heating) using a lake sediment reference sample. It was shown that the sample treatment in an autoclave with resistance heating provides the best fit (relative deviation < 7%) to certified values for metals generally used as diagenetic proxies (U, Sm, Nd, Th, La, Sc, Sr, etc.). Furthermore, the thermally convective pressure digestion appears to be more cost-efficient than microwave-assisted digestion (because of lower reagent consumption and cheaper removable PFE liners), an important asset for systematic geochemical mapping. In order to prove the applicability of the developed digestion procedure for different sediments, a marine sample from the East Siberian Sea was analyzed independently in two laboratories and across all representative metals the results acquired were found in good agreement.

Intracellular Zinc Quantification by Fluorescence Imaging with a FRET System.

Fluorescence imaging of cellular metals is widely reported. However, the quantification of intracellular metals with fluorescence imaging is so far not feasible and highly challenging. In this work, a ratiometric probe with two fluorescently labeled complementary DNA strains is designed for intracellular zinc quantification via fluorescence imaging, based on fluorescence resonance energy transfer (FRET) from carbon dots (CDs) to fluorescein (FAM). The donor CDs are modified with a Zn2+ aptamer, whereas the receptor FAM is conjugated with the complementary DNA sequence to ensure selectivity. MCF-7 cells are cultured sequentially with Zn2+ (20, 40, 55, 70, 85, and 100 μmol L-1) and CDs-FAM (100 μg mL-1), which is used for fluorescence imaging (at λex = 405 nm and λem = 440-490 nm for CDs, λem = 500-550 nm for FAM) to provide a relative fluorescence ratio (( F - F0)/ F0, F = ICDs/ IFAM), followed by quantifying intracellular zinc with ICPMS. A linear correlation is achieved between the relative fluorescence ratio in fluorescence images and the intracellular zinc content derived by ICPMS, which facilitates intracellular zinc quantification via fluorescence imaging. It is especially useful for real-time tracing of intracellular zinc during the cell culturing process or in vivo. The cellular uptake of Zn2+ by MCF-7 cells is further evaluated with this approach by culturing with 100 μmol L-1 of Zn2+ for different times, and a maximum uptake of 60.5 fg per cell is observed at an incubation time of 60 min. This value is further demonstrated well by ICPMS detection.

Source Apportionment and Heath Risk Quantification of Heavy Metals in PM2.5 in Yangzhou, China

Recently, a new method combining positive matrix factorization (PMF) and heavy metal health risk (HMHR) assessment was proposed to apportion sources of heavy metals in ambient particulate matter and the associated heavy metal cancer health risk (HMCR), which has been applied to data collected in Yangzhou, China. The annual average concentrations of six measured heavy metals were Pb (64.4 ng·m-3), followed by Cr (25.24 ng·m-3), As (6.36 ng·m-3), Ni (5.36 ng·m-3), Cd (3.34 ng·m-3), and Co (1.21 ng·m-3). The results showed that the major sources of PM2.5 were secondary sources (37.7%), followed by coal combustion (19.4%), resuspended dust (17.5%), vehicle emissions (16.9%), construction dust (5.2%), and industrial emissions (3.4%). As was primarily emitted from coal combustion, vehicle emissions, and resuspended dust. Co originated from industry emissions. Pb was mainly emitted from coal combustion. Ni and Cd were from industrial emissions. The major sources that contributed to HMCR were resuspended dust, coal combustion, vehicle emissions, industry emissions, and construction dust. The high contributions of resuspended dust and coal to HMCR were likely due to the high heavy metals concentrations in coal and the resuspended dust profile as well as high emissions of these sources.

Assembly of a heterodinuclear Mn/Fe cofactor is coupled to tyrosine\u2013valine ether cross-link formation in the R2-like ligand-binding oxidase

R2-like ligand-binding oxidases (R2lox) assemble a heterodinuclear Mn/Fe cofactor which performs reductive dioxygen (O2) activation, catalyzes formation of a tyrosine–valine ether cross-link in the protein scaffold, and binds a fatty acid in a putative substrate channel. We have previously shown that the N-terminal metal binding site 1 is unspecific for manganese or iron in the absence of O2, but prefers manganese in the presence of O2, whereas the C-terminal site 2 is specific for iron. Here, we analyze the effects of amino acid exchanges in the cofactor environment on cofactor assembly and metalation specificity using X-ray crystallography, X-ray absorption spectroscopy, and metal quantification. We find that exchange of either the cross-linking tyrosine or the valine, regardless of whether the mutation still allows cross-link formation or not, results in unspecific manganese or iron binding at site 1 both in the absence or presence of O2, while site 2 still prefers iron as in the wild-type. In contrast, a mutation that blocks binding of the fatty acid does not affect the metal specificity of either site under anoxic or aerobic conditions, and cross-link formation is still observed. All variants assemble a dinuclear trivalent metal cofactor in the aerobic resting state, independently of cross-link formation. These findings imply that the cross-link residues are required to achieve the preference for manganese in site 1 in the presence of O2. The metalation specificity, therefore, appears to be established during the redox reactions leading to cross-link formation.

CONCENTRATION OF ALUMINUM, IRON AND MANGANESE IN URBAN RIVERS LOCATED IN A COVERAGE AREA OF THE GUARANI AQUIFER IN LAGES - SC

The objective of the current study was to evaluate the concentration of aluminum (Al), iron (Fe) and manganese (Mn) on water and on the sediment of urban rivers (Carahá, Caveiras and Ponte Grande) in Lages, located on the mountain region of Santa Catarina, placed in a coverage area of the Guarani Aquifer. The water and sediment samples were collected between May and October of 2016 in three urban rivers, following an environmental disturbance gradient. For the extraction of the metals present on the sample, it was used the methods 3030 - Standard Methods of Water and Wastewater (2005) for the water samples and ISO 11,466 (1995) for the sediment samples. The quantification of metals was performed through a high- resolution spectrometer with atomic absorption, with a flame automation (acetylene-air or nitrous oxide-air). To evaluate the quantification, it was used a certified material (SRM 2709a - San Joaquin Soil - NIST). On the water samples were found concentrations of Mn above of class III, defined by the Resolution 357/05 of the Environment National Board-Brazil. The Pearson correlation matrix showed a positive correlation between the variables Al/Fe, Fe/Mn e Al/Mn on sediment and Fe/Mn on water. For the sediment, it was found high concentrations of Al, Fe, and Mn in some of the samples. By the results found, it is evinced an increase in the concentration of Al and Fe on the Carahá river sediment, and concentrations of Al, Fe, and Mn on the Ponte Grande river sediment, on the spots located at Lages - SC.

Trace Metals in Groundwater of the South Eastern Piedmont Region of Mount Cameroon: Quantification and Health Risk Assessment

The South Eastern Piedmont Region of Mount Cameroon is getting in-creasingly populated. Groundwater is the main resource for drinking in this area; hence, the quantification of trace metals, suitability and quality of the groundwater resources for drinking, domestic and agro-industrial uses is of public and scientific concern. In this study, 10 samples were collected from 10 sites in September 2017. Field measurement of physicochemical parameters and investigation of the levels of trace metal content in groundwater was determined using Inductively Coupled Plasma Mass Spectroscopy ICP-MS. R-mode statistical analysis has been done and traces metals elements correlated with the physicochemical parameters and cluster analysis PCA carried out. The paper also highlights and determines the average daily dose ADD, the carcinogenic risks CR and the non-carcinogenic risk hazard quotient HQ which yields the hazard indices HI. The general trend of mean trace metal concentration in the sampled groundwater was in the order of: Zn > Fe > Al > V > Mn > Cu > Cr > Ni > Pb > As > Co > Cd > Sb. All the groundwater risk indices; ADD, CR, HQ and HI were less than 1 in categories of insignificant health risk. The severity of metal toxicity is governed by several factors, such as dose, nutrition, age, and even life style. Therefore, this low trend might not guarantee the complete absence of human health risk. Generally, from risk assessment on trace metals using risk indices, the analyzed water samples might not be at an alarming health risk. However, due to an increasing level of environmental pollution that might be imposed by increasing human activity in this region, water sources might become a potential sink of contaminants; this is significant reason that makes constant monitoring, implementation and treatment of groundwater for drinking purposes obligatory.

Quantification of toxic metals during different winemaking stages

Heavy metals in beverages can constitute serious problems to human health. Consumption of wine may contribute to the daily dietary intake of pollutants, especially of toxic (heavy) metals. These compounds are also known as priority pollutants due to their potential toxic effects, if concentrations are not kept under allowable limits. Many characteristics such as: quality, origin, aroma and health safety of wine are influenced by environmental and anthropogenic factors. Hence, the contamination of wine by priority pollutants may occur at different stages of vine-growing, due to the application of agricultural chemicals, or at different stage of winemaking and ageing, because of the extended contact of wine with winemaking equipment materials (aluminium, brass, glass, stainless steel and wood, etc.), or chemicals used for cleaning and sanitation. The aim of this study is to identify and quantify the heavy metal ions from red wines. A particular focus was attributed to Zn and Cd from destemming-pressing-filtration-bottling stages in Fetească neagră grape variety from Cotnari vine growing region of Romania. Results indicated that heavy metals were linked to diverse Zn and Cd sources and complexes during the winemaking processes. Concentration of Zn and Cd were generally higher in must than in wine, although heavy metals concentrations were lower than the limits recommended by the International Organization of Vine and Wine for human health safety.

Isoflavone Stability, Quality Control Assessment and Clinical Safety of Q-CAN® Plus, a Novel Fermented Beverage

There is substantial data that fermented products have a diverse range of health benefits ranging from immunomodulation, improving lipid profiles and more recently positive effects on the microbiome. Despite these desirable clinical attributes there are practical barriers to the use of fermented products. Two such barriers are that many studies were performed using experimental products, and lacked careful characterization of content, stability, toxicology and safety. To overcome these issues, we identified a widely available fermented product (BESO Q-CAN® Plus) and i) conducted independent analysis of total isoflavone content, aerobic bacteria, yeast and mold plate counts, quantification of heavy metals, solvents, and ii) performed a safety clinical trial in 10 lean and 10 obese healthy subjects who consumed Q-CAN® Plus for 4 weeks, with a further 8 week follow-up. Q-CAN® Plus had 120.9 mg/100 ml of total isoflavones. Bacteria, mold, yeast were all below the normal limits. A profile of 300 herbicides, pesticides, fungicides and solvents was negative. Lead, mercury, arsenic and cadmium were below the detectable limit. A 24-month stability study demonstrated no decrease in the concentration of isoflavones and no microbiological contamination. The clinical trial demonstrated that Q-CAN® Plus was well tolerated. This independent analysis of Q-CAN® Plus demonstrated a stable isoflavone content, absence of a wide range of potential toxins and stability over 24 months. Q-CAN® Plus was also well tolerated. These data provide the information required for the safe use of an easily available fermented soy product.

Elemental characterisation of the pyramidal neuron layer within the rat and mouse hippocampus.

A unique combination of sensitivity, resolution, and penetration make X-ray fluorescence imaging (XFI) ideally suited to investigate trace elemental distributions in the biological context. XFI has gained widespread use as an analytical technique in the biological sciences, and in particular enables exciting new avenues of research in the field of neuroscience. In this study, elemental mapping by XFI was applied to characterise the elemental content within neuronal cell layers of hippocampal sub-regions of mice and rats. Although classical histochemical methods for metal detection exist, such approaches are typically limited to qualitative analysis. Specifically, histochemical methods are not uniformly sensitive to all chemical forms of a metal, often displaying variable sensitivity to specific "pools" or chemical forms of a metal. In addition, histochemical methods require fixation and extensive chemical treatment of samples, creating the strong likelihood for metal redistribution, leaching, or contamination. Direct quantitative elemental mapping of total elemental pools, in situ within ex vivo tissue sections, without the need for chemical fixation or addition of staining reagents is not possible with traditional histochemical methods; however, such a capability, which is provided by XFI, can offer an enormous analytical advantage. The results we report herein demonstrate the analytical advantage of XFI elemental mapping for direct, label-free metal quantification, in situ within ex vivo brain tissue sections. Specifically, we definitively characterise for the first time, the abundance of Fe within the pyramidal cell layers of the hippocampus. Localisation of Fe to this cell layer is not reproducibly achieved with classical Perls histochemical Fe stains. The ability of XFI to directly quantify neuronal elemental (P, S, Cl, K, Ca, Fe, Cu, Zn) distributions, revealed unique profiles of Fe and Zn within anatomical sub-regions of the hippocampus i.e., cornu ammonis 1, 2 or 3 (CA1, CA2 or CA3) sub-regions. Interestingly, our study reveals a unique Fe gradient across neuron populations within the non-degenerating and pathology free rat hippocampus, which curiously mirrors the pattern of region-specific vulnerability of the hippocampus that has previously been established to occur in various neurodegenerative diseases.

GROUNDWATER CHARACTERIZATION IN SOUTHWESTERN ROMANIA USING FUZZY HIERARCHICAL CROSS CLUSTERING

A simultaneous hierarchical classification of groundwater in the Banat Plain-southwestern Romania and associated characteristics such as As(III), As(V), total As, trace metals (Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn), pH and redox potential using Fuzzy Hierarchical Cross Clustering Algorithm was carried out. In samples containing more than 10 g/L total As (13.9 77.3 g/L), the As(V) species represented 57 20% and 73 18% in the others. Arsenic speciation pattern was in agreement with basic pH (8.31 8.49) and oxidizing conditions (369.0 409.1 mV) in aquifer. The contents of metals were below the threshold values excepting Mn. The Fuzzy Hierarchical Cross Clustering Algorithm emphasized pH and redox potential as main parameters responsible for water samples grouping. Part of water samples containing > 10 g/L As have as associated parameters the content of Pb, Cr, Zn and Fe, and pH plays a key role in natural occurrence of these elements by desorption from Fe minerals/oxyhydroxides. The other water samples with > 10 g/L As were grouped based on redox potential, As (III), As (V), total As, Cd, Ni, Cu, Al and Mn concentrations. The source of these elements was attributed to desorption processes from Al minerals/oxyhydroxides and Mn oxyhydroxides governed by the redox potential. The Fuzzy Hierarchical Cross Clustering emphasized the importance of trace metals quantification for classification of groundwater with naturally enriched As content.

XRF techniques to quantify heavy metals in vegetables at low detection limits

Sample preparation techniques, measurement routines and custom calibrations were developed and optimized for the quantification of Pb and additional heavy metals in dried and wet consumable vegetable tissues via WD-XRF and/or portable ED-XRF spectroscopy. After mitigating matrix influences fundamental to XRF quantification of heavy metals in a carbon matrix, the custom measurement and calibration routines were capable of detecting and quantifying Pb in dried prepared vegetable samples at concentrations relevant to the World Health Organization. The viability of each calibration was evaluated with measurements of vegetables grown in metals-rich garden soil collected from residential properties. Although robust calibrations for dried vegetables were obtained with WD-XRF, the slight compromise in the precision and accuracy of measurements with portable ED-XRF is offset by the portability of this technology. Heavy metal concentrations in wet coarsely-homogenized raw consumable vegetable tissues were quantified; however, further work is needed to test the viability of ED-XRF calibrations.

Determination of heavy metals in sunflower seeds by atomic absorption spectroscopy based on fractional mineralization

The actual problem of food chemistry is the contamination of food raw materials and food products with heavy metals. Modern physico-chemical methods for the quantification of heavy metals are highly accurate and allow even trace amounts of elements to be determined, but the complexity of the sample preparation procedure is one of the most time-consuming steps, requiring high costs of reagents and time, especially for analysis of fat-containing samples. In this regard, development of new ways of determination of content of heavy metals in olive raw materials is relevant. Sunflower seeds in which they established the maintenance of toxic elements with use of different ways of sample preparation have acted as an object of a research: dry combustion and a wet mineralization and the developed new way of a fractional mineralization which distinctive features are: preliminary decomposition of test on fatty (oil) and fat-free (oilcake) of fraction with their independent mineralization. Oilcake is exposed to combustion at the maximum temperature 400 ?С for two full cycles, with convertion of the mineralizat in background solution and definition of metals by AAS-ETA method, oil – is dissolved in bipolar solvent in the ratio 1:6:2 from the mass of oil, with the subsequent direct input of mix in an analytical cell of the graphite tubular furnace of an electrothermal atomizer where there is a mineralization and simultaneous atomization of test. The use of fractional mineralization makes it possible to improve the metrological characteristics of the atomic absorption method of sunflower seeds: to increase the average openability of the investigated elements to 90.8%, to reduce the error of convergence (by 4.5%) and the reproducibility (by 4.9%) of the results of the study of cadmium and lead, and also to reduce the total time of sample preparation for 4–6 hours as compared with the test methods.

EFECTOS DEL ARSÉNICO SOBRE LA MICROBIOTA BACTERIANA ACUÁTICA DEL RÍO GUAYLLABAMBA EN LA COMUNIDAD CORAZÓN DEL CHONTALINTAG

The objective of this research was to evaluate the transformation suffered by the aquatic microbial communities of the Guayllabamba River due to Arsenic (As) as a product of mining production waste, as well as to identify bacterial species and analyze their ecological status through diversity indexes. Three sampling points were established in the Guayllabamba River. The first one can be found at the mine water contamination point (M1), the second one is 1.5 km downstream from the pollution site (M2) and the third one, 1.5 km upstream from the contamination point (M3). For the quantification of heavy metals, atomic absorption reading techniques are used. Molecular identification was also carried out through the DGGE analysis of the 16s rDNA. The results showed that the bacterial communities were reduced and specialized in the cause of the different types of animals in the previous points. Thus, concentrations of As (0.009 mg/l) were found in sample M1, concentrations of As (0.005 mg/l in sample M2 and finally, the sample M3 showed concentrations of As (0.004 mg/l). In the multidimensional scaling of the banding pattern, it was observed that M1 and M2 have a 60% of similarity to each other and 5% similarity to M3 The most representative genera in the DGGE analysis were: Firmicutes (29.41%), Proteobacteria (23.52%), Bacteroidetes (17, 64%), Actinobacteria (11.76%), Cyanobacteria (17.67%).

Novel extraction induced by microemulsion breaking for Cu, Ni, Pb and V determination in ethanol-containing gasoline by graphite furnace atomic absorption spectrometry

This paper describes a detailed study on the determination of Cu, Ni, Pb, and V in ethanol-containing Brazilian commercial gasoline by graphite furnace atomic absorption spectrometry (GF AAS) after application of the novel extraction induced by microemulsion breaking (EIMB) for the extraction of analytes from the sample. EIMB is based on the formation and breaking of microemulsions with the sample and an extractant acid solution (typically HNO3 solution) in the presence of a dispersant agent (typically a short-chain alcohol). After microemulsion breaking, the following two phases are formed: (i) a top phase containing the remaining gasoline and (ii) a bottom phase containing the extracted metals in a medium composed of water, the dispersant agent, and ethanol, which was already present in the Brazilian gasoline. The bottom phase is collected and used for metal quantification by GF AAS. Several parameters that could affect the performance of the method were evaluated. Under optimized conditions, the microemulsion was prepared by mixing 4.6 mL of the sample with 0.35 mL of 1-propanol and 0.05 mL of a 3.5 mol L−1HNO3 solution. The microemulsion was shaken for 5 min at 110 rpm to enhance the extraction and was then disrupted by the addition of 0.40 mL of a 3.5 mol L−1 HNO3 solution. The bottom phase formed under these conditions was taken for metal determination by GF AAS. The limits of detection of the method for Cu, Ni, Pb and were 0.7, 0.1, 0.8 and 1.6 μg L−1, respectively. The method was applied in the analysis of five Brazilian gasoline samples, which presented concentrations of Cu, Ni, Pb, and V in the range of 7.1–63 μg L−1, 1.6–2.8 μg L−1, 5.3–9.7 μg L−1, and 24–44 μg L−1, respectively. Recovery tests were performed to assess the accuracy of the proposed method, with observed satisfactory recovery percentages of 87–116%.