Scielo RSS <![CDATA[Journal of the Brazilian Chemical Society]]> vol. 28 num. 12 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Rare Earth-Indomethacinate Complexes with Heterocyclic Ligands: Synthesis and Photoluminescence Properties]]> In this work, synthesis, characterization and photophysical properties of trivalent rare earth complexes with a nonsteroidal anti-inflammatory drug [the indomethacinate (indo), presenting formulas RE(indo)3(H2O)x (x = 3, for Eu3+ and Gd+3, and x = 4 for Tb+3), RE(indo)3(bipy) and RE(indo)3(phen) (bipy: 2,2'-bipyridine, and phen: 1,10-phenanthroline)] were investigated. Based on photoluminescent results, the intramolecular energy transfer process from T1 triplet states of indo, phen and bipy ligands to the 5D0 emitting level of the Eu3+ ion in the coordination compounds is discussed. Accordingly, it is proposed two possible intramolecular energy transfer mechanisms between indomethacinate ligand and rare earth ions, which involve the participation of excited electronic states of the heterocyclic ligands as intermediate ones. <![CDATA[Application of Response Surface Modeling and Chemometrics Methods for the Determination of Ofloxacin in Human Urine Using Dispersive Liquid-Liquid Microextraction Combined with Spectrofluorimetry]]> Dispersive liquid-liquid microextraction (DLLME) and spectrofluorimetry, coupled with chemometrics methods, are proposed in this work for the pre-concentration and determination of ofloxacin concentration in spiked human urine. Chloroform and acetonitrile were selected as the extraction and dispersive solvents by the one-variable-at-a-time process. The Box-Behnken design was used to optimize the other variables, including the volume of extraction and dispersion solvents, solution pH, and ionic strength. A linear calibration curve was obtained in the 5.0-120.0 ng mL-1 range under optimal conditions with a detection limit of 1.61 ng mL-1 and correlation coefficient of 0.9948. A relative standard deviation (RSD) of 1.13% was obtained for seven consecutive replicates. Parallel factor analysis (PARAFAC) and partial least square (PLS) modeling were applied for the multivariate calibration of the spectrofluorimetric data. To pre-process the data matrices and predict the model results, the orthogonal signal correction (OSC) was used, and the analysis results were statistically compared. The methods accuracy values for ofloxacin determination, evaluated by the root mean square errors of prediction (RMSEP) and relative standard error of prediction (RSEP), were 0.82 and 1.12 using OSC-PLS, and 0.31 and 0.42 using OSC-PARAFAC models, respectively. Ofloxacin can be reliably determined in human urine samples through the proposed procedure, according to the results. <![CDATA[Synthesis, Characterization and Enhanced Photocatalytic Activity of Iron Oxide/Carbon Nanotube/Ag-doped TiO<sub>2</sub> Nanocomposites]]> A novel magnetically recoverable catalyst (Fe/MWCNT/TiO2-Ag) was prepared in this study by a process that involves few steps. Titanium dioxide doped with silver and iron oxide was deposited on support of multi-walled carbon nanotubes (MWCNT). The synthesized catalysts were characterized by inductively coupled plasma mass spectrometry (ICP-MS), N2 adsorption/desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), infrared spectroscopy (IR) and UV-Vis diffuse reflectance spectra (DRS). Phenol in aqueous solution (50 mg L-1) was used as a model compound for evaluation of UV-Vis (filter cut off for l &gt; 300 nm) photocatalytic activity. The composite catalyst has a high photocatalytic activity, destroying ca. 100% of phenol and removing 85% of total organic carbon in an aqueous solution after 180 min. The Fe/MWCNT/TiO2-Ag catalyst remained stable, presenting an 8% decrease in phenol degradation efficiency after ten consecutive photocatalytic cycles. <![CDATA[Natural Organic Acid as Green Catalyst for Xanthenones Synthesis: Methodology, Mechanism and Calcium Channel Blocking Activity]]> Xanthenones were synthesized via one-pot tricomponent reaction, under solvent-free conditions, using aldehydes, phenolic and cyclic 1,3-dicarbonyl compounds. Natural organic acids (NOAs), compounds present in many living metabolisms, were used as potential green catalysts. NOA are considered to be more eco-friendly and user-friendly alternative to traditional methodologies. Optimization studies showed that oxalic acid was the best NOA catalyst for such reaction furnishing the xanthenones with up to 93% of yield. Theoretical calculations were performed to evaluate this reaction mechanism and regioselectivity. The results showed that the regiospecificity of this three-component reaction is kinetically and thermodynamically controlled by the addition of β-naphthol C2, instead of C10, to the aldehyde. Our results also disclosed two xanthenones as novel calcium channels blockers. Eco-friendly reaction conditions, easy workup procedure, short reaction times and good yields are some of the advantages of our methodology. <![CDATA[Application of Factorial Design for Optimization of the Synthesis of Lactulose Obtained from Whey Permeate]]> There is a great interest in developing suitable alternatives for the utilization of whey, a by-product from cheese production that contains high concentration of lactose. These alternatives allow the transformation of whey into several products, reducing its environmental impact and providing gains to the dairy industry through the development of new products. The goal of this study was to optimize the synthesis of lactulose from the permeate of bovine whey. The response surface methodology (RSM) was used to investigate the effect of two parameters, time of reaction (90, 135 and 180 min) and isomerization type (sodium sulfite, boric acid and b-galactosidase enzyme), aiming to obtain the highest reaction yield. According to the response surface and desirability function, the best experimental conditions for lactulose synthesis (where it was obtained 50.06 g of lactulose per 100 g of whey powder) consisted of a reaction time of 180 min with the use of enzymatic isomerization. <![CDATA[New 9-Aminoacridine Derivative: Synthesis, Study and Potential Application as pH Indicator in Organic Solvents]]> In this work, we describe the synthesis of a novel 9-aminoacridine derivative that presents surprisingly different colors when exposed to neutral, acidic or basic mediums with potential application as pH indicator in organic solvents. Furthermore, pKa and molar absorptivity values were determined and theoretical studies supported by density functional theory (DFT) calculations were performed to elucidate the different structures of this compound. <![CDATA[Exploiting Cork as Biosorbent Extraction Phase for Solid-Phase Microextraction to Determine 3-(4-Methylbenzylidene)camphor and 2-Ethylhexyl 4-(Dimethylamino)benzoate in River Water by Gas Chromatography-Mass Spectrometry]]> In this study, a method for the determination of 3-(4-methylbenzylidene)camphor (4-MBC) and 2-ethylhexyl 4-(dimethylamino)benzoate (OD-PABA) in river water samples employing cork as the SPME (solid-phase microextraction) fiber was developed. The extraction parameters optimized were pH, ionic strength and extraction time and temperature. For the extraction step, the sample pH was studied in univariate experiments while the extraction time, temperature and ionic strength were evaluated using a central composite design. The optimal extraction conditions were sample pH 4.0, extraction time 70 min, sample temperature 80 °C and sodium chloride concentration 6% (m v-1). The limits of quantification for 4-MBC and OD-PABA were 0.1 and 0.01 µg L-1, respectively. The linear correlation coefficients were greater than 0.97 for both analytes and the developed method showed recovery values between 67 and 107%. In an evaluation of the fiber-to-fiber reproducibility (fibers produced by different analysts), the relative standard deviation (RSD) was lower than 11% (n = 6). <![CDATA[Separation and Identification of Functional Groups of Molecules Responsible for Fluorescence of Biodiesel Using FTIR Spectroscopy and Principal Component Analysis]]> In order to separate and identify functional groups of molecules responsible for fluorescence compounds present in biodiesel, a column chromatography coupled with infrared spectroscopy and multivariate analysis was performed. A biodiesel sample was packed in a chromatographic column and the fractions obtained were used to perform the analyses. Before undergoing the separation process, the biodiesel sample was analyzed by light emitting diode (LED)-induced fluorescence and compared its spectrum with β-carotene and soybean oil patterns. The low cost and speed of analysis suggest that this technique can be used in the separation of biodiesel substances. The fluorescence emission spectra allowed identifying molecules such as β-carotene, in which the spectrum of its pattern exhibited fluorescence within a region ranging from 500 to 700 nm and chlorophyll molecules. When soybean oil is excited at around 405 nm, it features a fluorescent emission band within the region of 670 nm, which reveals the presence of chlorophyll. Infrared spectroscopy coupled with principal component analysis allowed to discriminate the fractions and to identify the functional groups of compounds present in the sample. <![CDATA[Determination of Selenium in Bovine Semen by ICP-MS Using Formic Acid for Sample Preparation]]> Determination of Se by inductively coupled plasma mass spectrometry (ICP-MS) can be difficult due to spectral interferences; however, these interferences can be eliminated by using collision-reaction interface (CRI) technology. A simple and fast procedure for determination of total Se concentration in bovine semen by ICP-MS after sample solubilization with diluted formic acid is here proposed. Formic acid caused an increase of up to 50% in selenium net signals and the maximum gain was obtained at 10% v v-1 formic acid solution. The optimized nebulizer gas flow rates were 1.05 and 0.95 L min-1, and radio frequency applied power were 1.3 and 1.4 kW without and with CRI, respectively. Microwave-assisted acid digestion was also implemented in the preparation of semen sample for comparison of results. No statistical differences between these sample preparation strategies at 95% confidence level (t-test) were observed for 76Se+, 77Se+, 78Se+ and 82Se+ without using CRI and 82Se+ with CRI. <![CDATA[Combination of Propylene Glycol Alginate and Lauric Acid on Water Retention and Mechanical Properties of Soy Protein Isolate-Based Films]]> The water sorption, water barrier properties and mechanical behavior of soy protein isolate (SPI) based films combined with propylene glycol alginate (PGA) and lauric acid (La) via a direct- or co-dried blending process were investigated. Higher water retention ability and a single glass transition temperature (Tg) were found when the PGA was added to form different ternary co-dried blending films by a co-drying process, indicating their compatibility. Tg was reduced in the case of higher relative humidity and incorporation of La. The response surface methodology (RSM) indicated that the effect of La content was highly significant (p &lt; 0.05) for the water retention ability and mechanical properties, and the proposed models calculated for the tensile strength and elongation at break showed a good fit. The results revealed the importance of the interactions among lipids, protein and polysaccharide in composite films which also provided evidence for modeling film behavior. <![CDATA[Effect of Endophytic Fungal Associations on the Chemical Profile of <em>in vitroVochysia divergens</em> Seedlings]]> Vochysia divergens (Vochysiaceae) is considered an invasive species in the wetlands of the Brazilian Pantanal, which hinders the cultivation of agricultural species. In this study, we evaluated the chemical profile by HPLC-DAD (high-performance liquid chromatography-diode array detector) of leaves extracts from V. divergens seedlings inoculated with endophytic fungi isolated from V. divergens roots. These fungi were collected on dry (D) and wet (W) seasons in the Pantanal. The presence of tannin hexahydroxydiphenoyl (HHDP)-galloyl-glucose and flavone 3',5'-dimethoxy-luteolin were predominant in the seedlings inoculated with endophytic fungi W experiments at 100 and 80%, respectively. Likewise, flavone 3',5-dimethoxy-luteolin-7-O-β-glucoside showed a similar representation in the two evaluated periods, compared with 5-methoxy-luteolin, which was detected only in seedlings inoculated with W endophytic fungi. This approach is new to V. divergens, which has no scientific data on its in vitro elicitation, in the search for a better understanding of the ecological relationships of this species. <![CDATA[Spatial and Temporal Variations in Secondary Metabolites Content of the Brazilian Arnica Leaves (<em>Lychnophora ericoides</em> Mart., Asteraceae)]]> The genus Lychnophora (Asteraceae) is a medicinal plant traditionally used as anti-inflammatory or analgesic agent. Its biological properties have been widely investigated and correlated with its chemical composition, which could be different between the species and even accordingly to the place and season of collection. In this work, it was investigated the spatial and temporal variations in the secondary metabolites from five populations of Lychnophora ericoides. Among them, a more diversified secondary metabolism was observed for the plants collected at Ibiraci-MG (Brazil), a city placed between two biomes, Cerrado and Atlantic Forest. The highest concentrations of chlorogenic acids were found in the Cerrado dry season (winter), while the flavonoids were higher during the rainy season (summer). Significant reduction was observed in the contents of all the secondary metabolites in old leaves, and also in flowery branches. These variations detected in L. ericoides leaves could highly influence the intensity of the biological activities of this plant. <![CDATA[New Alternative to Produce Colored Polymer Nanocomposites: Organophilic Ni/Al and Co/Al Layered Double Hydroxide as Fillers into Low-Density Polyethylene]]> Green (Ni2+/Al+3) and pink (Co2+/Al+3) layered double hydroxides (LDH) (molar ratio of 3:1) were intercalated with several organic anions and used as functional colored fillers into low density polyethylene (LDPE) by melt mixing in amounts of 0.2 to 7 wt.%. Scanning electron microscopic (SEM) results of LDPE nanocomposites indicated that with low percentage of filler, all the LDH samples showed efficient delamination/exfoliation in the polymer matrix. Fillers added to LDPE with concentrations of 0.2, 0.5, 2 and 5% presented, in general, maintenance of Young's modulus and tensile strength, tending to the reduction with a loading of 7%. Most of the nanocomposites presented similar elongations, although NiUS stood out, with an elongation increase of 300%. Differential scanning calorimetry (DSC) indicated the effect of the Co/Al-LDH in inducing the formation of LDPE crystalline domains, especially at higher temperature than neat LDPE. <![CDATA[Influence of the Transport of Sea Spray on the Salinization of the Semiarid Region Waters (Bahia, Brazil)]]> The sea spray can be transported to long distances, reaching the semiarid regions. In this work, the rainwater and the atmospheric particulate matter were characterized by investigating the presence of sea spray in the atmosphere of the semiarid region of Bahia, Brazil, aiming to study the influence of its transport on the salinization of the waters of the region. Stable isotopes of deuterium and oxygen-18 were also determined in the rain as environmental tracers, evaluating the isotopic ratios 18O/16O and D/H. The atmosphere of the region suffers marine influence, as well as resuspended soil particles and anthropogenic sources. The results demonstrate that the amount of sea spray which reaches the region is insufficient to interfere at the groundwater composition and the cause of its salinization should be attributed to the local geology and the evaporation and salt concentration process due to the high temperatures found in the region. <![CDATA[ITO Obtained by Spray Pyrolysis and Coating on Glass Substrate]]> Conductive thin films have various applications in different technological fields. Indium tin oxide (ITO) is a mixed oxide. In the film form, ITO has been widely employed as electrode in many optoelectronic devices. Methods like thermal evaporation, sputtering, chemical vapor deposition (CVD), electron beam, spray coating, and sol-gel synthesis give ITO thin films. In this work, we prepared ITO thin films by dip coating of a glass substrate into ITO obtained by spray pyrolysis. ITO consisted of spherical particles with different diameters. The ITO thin films were treated with laser. X-ray diffraction (XRD) analysis confirmed that spray pyrolysis produced spherical ITO particles. Transmittance analyses revealed the production of transparent films with thickness ranging from 0.800 to 1.200 µm. The four-wire test showed that the porosity of the films led to low conductivity. Film resistance was a function of the number of layers of ITO thin film. <![CDATA[Development of Manual Shaking and Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction for Analysis of Organophosphorus Pesticides in Aqueous Samples]]> A novel, rapid and efficient manual shaking and ultrasound-assisted surfactant-enhanced emulsification microextraction (M-UASEME) combined with gas chromatography-flame photometric detection (GC-FPD) was developed for the extraction and determination of eight organophosphorus pesticides (OPPs) in tap water and honey samples. The main parameters that affected the extraction efficiency were investigated and optimized. Under the optimum conditions, the relative standard deviation (RSD, n = 6) ranged from 2.4 to 9.3%. Limits of detection (LOD) were varied between 0.005 and 0.05 µg L-1. Good linearity was obtained in a range of 0.5-50.0 µg L-1 for all analytes with the correlation coefficients (r) &gt; 0.9964. Finally, the developed method was successfully applied to determine the eight pesticide residues in real samples. The recoveries of the target analytes in samples were between 82.4 and 96.7%. <![CDATA[Evaluating the Potential of Biodiesel Production through Microalgae Farming in Photobioreactor and High Rate Ponds from Wastewater Treatment]]> In the last decade, the research works on microbial as a potential source of lipid for biodiesel production have been growing. In this work, the potential of a sludge from high-rate lagoons in urban sewage treatment, composed mainly by Chlorella sp., as oil source for biodiesel production, was studied. The potential of Chlorella sp. growth in photobioreactor under controlled conditions was also investigated. Low lipid content (up to 3%) was observed in both cases. The composition of both oils showed high amount of fatty acids and fatty acid based compounds, however there are also other non-fatty acid based lipids. Density and viscosity of biodiesel from biosolid oil were determined and the results showed that these physico-chemical properties do not match the specification required for biodiesel. The results showed that sewage sludge from Samambaia treatment station (DF, Brazil) and Chlorella sp. cultivated under the conditions described in this work are not potential sources of fatty material for biodiesel production. <![CDATA[Simultaneous Determination of Nonylphenol and Nonylphenol Ethoxylates in Wastewater Samples from Biodegradation Process by High Performance Liquid Chromatography Method]]> The degradation products of nonylphenol ethoxylates (NPnEO), nonylphenol (NP) and short-chain NPnEO are representative of environmental endocrine disruptors. They possess strong lipophilicity, toxicity, cumulative property and estrogenic effect. They can pollute the environment, cause body precocious, and induce the body's estrogen-sensitive cancer cell proliferation. A fast method using high performance liquid chromatography (HPLC) was developed to simultaneously quantify NP and 11 kinds of NPnEO in wastewater samples. The influence of mobile phase composition, mobile phase ratio, mobile phase flow rate, column temperature and sample injection volume on the separation effect was studied. Under the optimized conditions, NP and 11 kinds of NPnEO were separated successfully within 35 min. The method showed good linearity for NP and 11 kinds of NPnEO (n = 1-11). The linear correlation coefficients for the standard curves were 0.9720- 0.9999. The precision degree of the method was reliable and all the relative standard deviation (RSD) values (n = 0-11) obtained were less than 5.0%. <![CDATA[Biodiesel Glycerides from the Soybean Ethylic Route Incomplete Conversion on the Diesel Engines Combustion Process]]> An evaluation was made to determine the effect of the glycerides presence resulting from the incomplete conversion of soybean biodiesel produced via alkaline catalysis and ethylic route on engine performance, and emissions in formulations containing 10 and 20% (m/m) of biodiesel used as additives in base diesel with low sulfur content and cetane ratings of 45 and 50. By way of comparison, similar formulations were used with soybean biodiesel methyl route with low concentration of glycerides. Tests on a diesel cycle engine with a mechanical fuel injection system indicated that the presence of glycerides decreases the volatility of biodiesel and increase the cetane number of fuels. The higher the cetane number, the higher the particulate matter emissions and the lower the unburned hydrocarbon emissions. Formulations with cetane number 50 showed higher emissions of particulate matter. The presence of glycerides in biodiesel reduces the fuel's vapor pressure, thereby increasing the cetane number and emissions of particulate matter and lower emissions of unburned hydrocarbons. The specific consumption of fuels formulated with biodiesel increases due to its lower enthalpy of combustion and to the presence of glycerides in fuels formulated with soybean biodiesel produced via the ethanol route. <![CDATA[Evaluation of Distribution and Bioaccumulation of Arsenic by ICP-MS in Tilapia (<em>Oreochromis niloticus</em>) Cultivated in Different Environments]]> The concentration of arsenic in tissues of tilapia was evaluated and an estimation of the risks associated with the consumption of this fish was done, taking into account the guidelines established by FAO/WHO. The inductively coupled plasma mass spectrometry (ICP-MS) technique in kinetic energy discrimination (KED) mode was employed and certified reference materials were analyzed with recoveries of 101, 110, and 80% from NIST 1640a (trace elements in water), NIST 1566b (oyster tissue), and DORM-3 (fish protein). In the consumable portion (the muscle fish tissue), the average concentration found was 0.030 ± 0.008 µg g-1, which is below the arsenic maximum level established by international regulatory agencies. The average concentration found in the viscera (stomach, gills, and liver) was 0.485 ± 0.225 µg g-1, concluding that the viscera had greater capacity for the bioaccumulation of arsenic. From this study was possible to monitor the arsenic element in different tilapia specimens evidencing its accumulation throughout the body of the fish. <![CDATA[Development and Validation of a Stability-Indicating Method for Perillyl Alcohol Incorporated in Poly(lactide-<em>co</em>-glycolide) Nanoparticles and Stress Degradation Studies]]> Perillyl alcohol has been studied in the treatment of cancer disease. However, its high toxicity is a drawback, which can be overcome by its incorporation in nanostructured systems. The aim of this work was to develop and validate a chromatographic method for determination of perillyl alcohol encapsulation efficiency in a polymeric nanoparticles formulation and evaluation of the presence of related degradation products. Perillyl alcohol was subjected to forced conditions of hydrolysis (acidic, alkaline and neutral), oxidation, photolysis and thermal stress, as suggested in the International Conference of Harmonization (ICH) guidelines. The drug showed significant degradation under acidic conditions. The degradation products could be adequately separated on an XBridge C18 column (100 × 2.1 mm, 3.5 µm) using isocratic elution (350 µL min−1) of water/acetonitrile (65 : 35, v/v) at 210 nm. Data from validation studies demonstrated that the method is selective, linear (coefficient of determination (R2) &gt; 0.999) over the range of 20.0-80.0 µg mL−1, precise (relative standard deviation (RSD) &lt; 2.0%), accurate (98.07 to 101.99%) and robust for minor changes. The method was successfully applied to determine the encapsulation efficiency of perillyl alcohol in polymeric nanoparticles, both for product development and for quality control purposes. After nanoparticles production, the presence of degradation products was not observed indicating that the single-emulsion solvent-evaporation technique used does not favor chemical degradation of the drug. <![CDATA[Anti-Trypanosoma Activity and Synergistic Effects of Natural and Semi-Synthetic Triterpenes and Predominant Cell Death through Autophagy in Amastigote Forms]]> Chagas' disease is a parasitic disease with unsatisfactory treatment, mainly in chronic stage. This study aimed to evaluate the trypanocidal activity and action mechanisms of α/β-amyrin and its semi-synthetic derivatives, together with four isolated natural triterpenes, tested against trypomastigote and amastigote forms. The structure-activity relationship was suggested and cytotoxicity was measured. In general, greater polar compounds may have improved the selectivity to the protozoan. Action mechanisms were only performed for the amastigotes of Trypanosoma cruzi by evaluating the ultrastructural alterations, membrane permeability, mitochondrial membrane potential and cell volume, since the majority of compounds displayed promising antiamastigote activities. Triterpenes promoted changes on mitochondrial membrane potential and ultrastructural features that suggest autophagy processes. Both combinations between α/β-amyrin and 3-O-acetyl-11-oxo-α/β-amyrin and 3-O-acetyl-α/β-amyrin with benznidazole displayed synergistic effects against amastigotes and antagonistic effects on LLCMK2 cells. The antiamastigote activities, chemical derivatization, drug combinations and action mechanisms revealed to be crucial approaches toward this chronic disease. <![CDATA[The Structure and Composition of Corrosion Product Film and its Relation to Corrosion Rate for Carbon Steels in CO<sub>2</sub> Saturated Solutions at Different Temperatures]]> For carbon steels immersed in CO2 saturated solutions at different temperatures, the structure and the composition of corrosion product film formed on the steel surface were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The corrosion rate of the steel was evaluated by potentiodynamic polarization, and the relation between the corrosion rate and the film property was discussed. The corrosion rate of the steel was very closely associated with the structure and the composition of corrosion product film, which were affected significantly by the solution temperature. From 30 to 60 ºC, the corrosion product film composed of FeCO3 was porous and poorly adherent, and the corrosion rate increased with the rise of temperature. At 70 and 80 ºC, the corrosion product film was also composed of FeCO3 and presented a compact and dense cubic crystal structure, resulting in the decrease on the corrosion rate. The corrosion rate increased once again when the temperature was up to 90 ºC, which was attributed to the negative effect of high temperature water vapor corrosion on the grain coarsening and the part exfoliation for the FeCO3 film. <![CDATA[Colorimetric Determination of Ascorbic Acid Based on Its Interfering Effect in the Enzymatic Analysis of Glucose: An Approach Using Smartphone Image Analysis]]> The use of digital image analysis as an analytical tool is a reality nowadays, and the use of smartphones stands out due to its high accessibility and practicality. Ascorbic acid (AA) is a natural and essential vitamin available as a supplement as a result of its use in preventing and treating several pathologies. This paper reports a simple, fast and low cost method using smartphone image analysis for quantification of AA based on its interfering effect in the enzymatic colorimetric detection of glucose. Commercial vitamin C tablets were used as prediction set for AA quantification, showing very satisfactory results (relative errors &lt; 4%), where no statistical difference at a 95% confidence level was observed between the AA content estimated by the imaging method and the labeled reference values. As advantages, this method does not use expensive reagents neither laborious procedures to carry out the analysis. <![CDATA[A Low-Cost Video-Based Reflectometer for Selective Detection of Cu<sup>2+</sup> Using Paper-Based Colorimetric Sensors]]> This paper presents a low-cost reflectometer for selective detection of Cu2+. The reflectometer is based on an emission light source using five light-emitting diodes at different wavelengths and a detector using a webcam. The samples were prepared using a filter paper-based colorimetric sensor with ascorbic acid-based quinoxaline derivative. Video analysis using gray color intensity was used to perform both copper ion screening (Cu2+, Pb2+, Cr+3, Ni2+, Fe2+, Sn2+, Mg2+, Cd2+, Ag+ and Co2+) and quantification of Cu2+ in spiked samples. In addition, a multivariate validation was performed. The system proved to be selective to Cu2+ among the screened ions, and its quantification was performed using partial least square regressions. Good linearity (R2 = 0.979, coefficient of determination), low root-mean-square error of prediction (RMSEP = 5.20 × 10-3 mol L-1) and high recovery (93.39-128.64%) were achieved. This method has potential to be employed for rapid and selective determination of Cu2+ in water using low-cost instrumentation.