Alejandra Carreon-Alvarez

Determination of Cu in Tequila by Anodic Stripping Voltammetry

Abstract Concentrations of metals such as copper in alcoholic beverages must be strictly regulated due to negative effects ranging from beverage spoilage and hazing, to sensorial and health consequences. In this paper, a voltammetric alternative is presented for the analysis of copper in tequila, a Mexican spirituous alcoholic beverage. Anodic Stripping Voltammetry is applied and the standard addition method is used to quantify copper in this beverage at concentrations commonly present in tequila (<10 ppm) without sample pretreatment. Copper can be reduced and then oxidized quantitatively and reproducibly. A comparison of Anodic Stripping Voltammetry with Atomic Absorption Spectrometry is presented.

Synthesis, Characterization, and Sensor Applications of Spinel ZnCo2O4 Nanoparticles

Spinel ZnCo2O4 nanoparticles were synthesized by means of the microwave-assisted colloidal method. A solution containing ethanol, Co-nitrate, Zn-nitrate, and dodecylamine was stirred for 24 h and evaporated by a microwave oven. The resulting solid material was dried at 200 °C and subsequently calcined at 500 °C for 5 h. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy, confirming the formation of spinel ZnCo2O4 nanoparticles with average sizes between 49 and 75 nm. It was found that the average particle size decreased when the dodecylamine concentration increased. Pellets containing ZnCo2O4 nanoparticles were fabricated and tested as sensors in carbon monoxide (CO) and propane (C3H8) gases at different concentrations and temperatures. Sensor performance tests revealed an extremely high response to 300 ppm of CO at an operating temperature of 200 °C.

Performance of three pilot-scale hybrid constructed wetlands for total coliforms and Escherichia coli removal from primary effluent – a 2-year study in a subtropical climate

Three pilot-scale two-stage hybrid constructed wetlands were evaluated in order to compare their efficiency for total coliforms (TCol) and Escherichia coli removal and to analyze their performances in two 1-year periods of experimentation. System I consisted of a horizontal flow (HF) constructed wetland (CW) followed by a stabilization pond. System II was also configured with a HF CW as a first stage which was then followed by a vertical flow (VF) CW as a second stage. System III was configured with a VF CW followed by a HF CW. In the first year of evaluation, the HF-VF system was the most effective for TCol removal (p < 0.05) and achieved a reduction of 2.2 log units. With regard to E. coli removal, the HF-VF and VF-HF systems were the most effective (p < 0.05) with average reductions of 3.2 and 3.8 log units, respectively. In the second year, the most effective were those with a VF component for both TCol and E. coli which underwent average reductions of 2.34-2.44 and 3.44-3.74 log units, respectively. The reduction achieved in E. coli densities, in both years, satisfy the World Health Organization guidelines that require a 3-4 log unit pathogen reduction in wastewater treatment systems.

Assessment of Physicochemical Properties of Tequila Brands: Authentication and Quality

Several physicochemical properties were measured in commercial tequila brands: conductivity, density, pH, sound velocity, viscosity, and refractive index. Physicochemical data were analyzed by Principal Component Analysis (PCA), cluster analysis, and the one-way analysis of variance to identify the quality and authenticity of tequila brands. According to the Principal Component Analysis, the existence of 3 main components was identified, explaining the 87.76% of the total variability of physicochemical measurements. In general, all tequila brands appeared together in the plane of the first two principal components. In the cluster analysis, four groups showing similar characteristics were identified. In particular, one of the clusters contains some tequila brands that are not identified by the Regulatory Council of Tequila and do not meet the quality requirements established in the Mexican Official Standard 006. These tequila brands are characterized by having higher conductivity and density and lower viscosity and refractive index, determined by one-way analysis of variance. Therefore, these economical measurements, PCA, and cluster analysis can be used to determinate the authenticity of a tequila brand.

Treatment of tequila vinasse and elimination of phenol by coagulation–flocculation process coupled with heterogeneous photocatalysis using titanium dioxide nanoparticles

ABSTRACT In this research, we are reporting the treatment of tequila vinasse by a coagulation–flocculation process coupled with heterogeneous photocatalysis using two types of titanium dioxide nanoparticles, i.e. (1) commercial nanoparticles, and (2) nanoparticles synthesized by sol–gel. The efficiency in the elimination of phenol, which is one of the most harmful contaminants in tequila vinasse, was also included in the evaluation of the treatment process. The synthesized titanium dioxide nanoparticles were annealed in air at 400°C for 1 h and were characterized by X-ray diffraction, transmission electron microscopy, ultraviolet-visible and Raman spectroscopy. Anatase phase was observed in both samples, with a crystallite size of 22.5 and 9.8 nm for commercial and synthesized nanoparticles respectively. Tequila vinasse was characterized before and after the treatments by measuring physicochemical parameters such as pH, chemical oxygen demand (COD), colour, total suspended solids (TSS), as well as using ultraviolet-visible spectroscopy and Raman spectroscopy to identify the presence of organic compounds, and gas chromatography (GC) for phenol quantification. Raw vinasse was treated initially by coagulation–flocculation producing clarified vinasse, which in turn was treated by photocatalysis for 3 h using hydrogen peroxide as oxidizing agent. The use of synthesized titanium dioxide nanoparticles allowed the highest efficiencies, reaching reductions of 99.4%, 86.0%, and 70.0% for TSS, colour, and COD respectively. GC results showed the reduction of phenol concentrations in 89.7% with our synthesized nanoparticles in contrast to 82.7% reduction, with commercial titanium dioxide nanoparticles. GRAPHICAL ABSTRACT