Mango peel, a by-product obtained from the industrialization of this fruit, is a promising and inexpensive source of phenolic compounds. In the present study, both the drying of the mango peel and the extraction of phenolic compounds were optimized using the response surface methodology. In this sense, temperature and charge/area ratio were selected as depend variables to drying process. Instead, for the ultrasonic assisted extraction (UAE) the temperature, ethanol-water concentration and time were optimized. For both processes, the total phenolic content (TPC) and mangiferin concentrations were the response variables. The TPC and the xanthone concentration were determined by the Folin-Ciocalteu method and HPLC-ESI-IT-MSn, respectively. The optimal conditions for the dehydration process were 54 °C and 2.3 kg m-2, reaching a TPC of 21.7 ± 1.6 mg GAE g-1 dw and a concentration of mangiferin of 1.94 ± 0.22 mg g-1 dw. Regarding to UAE, the optimum conditions were 51 °C, 50% ethanol and 71 min. Under these conditions, the TPC was 19.5 ± 0.8 mg GAE g-1 dw and the mangiferin concentration corresponded to 1.50 ± 0.13 mg g-1 dw. Additionally, 38 compounds were identified in the extract obtained under optimal conditions.

Resumen En el mundo, el café es el segundo producto más comercializado después del petróleo. Sin embargo, debido a su elevado precio, suele ser adulterado con materiales de menor costo. El objetivo de la presente investigación fue desarrollar un método basado en la combinación de las técnicas de microextracción de fase sólida (SPME) con la cromatografía de gases acoplado a espectrometría de masas (GC-MS) y el análisis de componentes principales (PCA), para detectar la presencia de haba y/o cebada en café tostado. Además, se optimizó la SPME de compuestos volátiles del café, mediante la metodología de superficie de respuesta. Respecto al método de extracción, se encontró que las condiciones óptimas fueron 16 y 35 min, para el tiempo de equilibrio y extracción, respectivamente. Por otra parte, se identificaron 44, 36 y 24 compuestos, en café, cebada y haba, respectivamente. De acuerdo con nuestro conocimiento, es el primer estudio respecto a la identificación de compuestos volátiles en haba tostada. Finalmente, el método desarrollado permitió detectar la probable presencia de haba en cuatro muestras comerciales de café. Además, se descartó la presencia de cebada en estas muestras.

Abstract Globally, coffee is the second most commercialized product after crude oil. Nevertheless, due to its high price, this product is usually adulterated with lower-cost products. The objective of the present study was to develop a method based on the combination of solid phase microextraction (SPME) with gas chromatography coupled to mass spectrometry (GC-MS) and principal component analysis (PCA), to detect the presence of faba beans and/or barley in roasted coffee. In addition, the SPME of volatile coffee compounds was optimized using the response surface methodology. The optimized SPME conditions were 16 min as conditioning time and 35 min as extraction time. Besides, 44, 36 and 24 compounds were identified, in coffee, barley and bean, respectively. Finally, the developed method allowed detecting the probable presence of faba bean in four commercial coffee samples. To our knowledge, this is the first time that volatile compounds have been described in roasted faba bean. In addition, the presence of barley in these samples was ruled out.

Abstract: In Ecuador the use of pesticides has been a problem due to the concentrations used are higher than the maximum allowable limits. The agencies that control this type of compounds do not have sophisticated technologies like tandem mass spectrometry or time of flight, and use the same equipment for different analysis. For these reason sometimes two columns are installed simultaneously, which consequently can be a problem with the maximum temperature that can use. The aim of this work was to develop a methodology to quantify 32 organochlorine pesticides by gas chromatography using electron capture detector and mass spectrometry with a low oven temperature. Different conditions of temperature ramp, stationary phase, injector temperature, carrier gas flow, purge flow and injection mode were evaluated. Only injector temperature and carrier gas flow had no effect on the peak area. Using a DB5-ms column and the same temperature ramp, 24 pesticides were separated. Although different oven temperature programs were tested, three pairs of pesticides shared the same elution time, but the identification was achieved using selected ion monitoring mode. The correlation coefficient of the calibration curves was greater than 0,99. The detection limits found were lower than the maximum residue levels allowed.

Resumen: El uso de pesticidas en Ecuador es muy amplio y las concentraciones utilizadas son superiores a los límites máximos permitidos. Las agencias que controlan este tipo de compuestos no cuentan con tecnología sofisticada como tiempo de vuelo, utilizando el mismo equipo para distintos análisis. Por esta razón, en algunos casos dos columnas son instaladas simultáneamente, lo que podría llegar a ser un problema con la temperatura máxima que se puede utilizar. El objetivo de este trabajo fue desarrollar una metodología que permita cuantificar 32 pesticidas organoclorados mediante cromatografía de gases utilizando los detectores de captura de electrones y espectrometría de masas con temperatura reducida. Se evaluaron diferentes condiciones de rampa de temperatura, fase estacionaria, temperatura del inyector, flujo del gas de arrastre, flujo de purga y tipo de inyección. Únicamente la temperatura del inyector y el flujo del gas de arrastre no tuvieron efecto sobre el área de los picos. Empleando la columna DB5-ms y una misma rampa de temperatura, se pudieron separar 24 pesticidas. Pese a que se emplearon distintos gradientes de temperatura, tres pares de pesticidas compartieron el mismo tiempo de retención, pero aplicando el monitoreo de iones seleccionados se logró identificarlos. El coeficiente de determinación de las curvas de calibración fue mayor a 0,99. Los límites de detección encontrados fueron menores a los límites máximos permitidos.

Four vegetal species of the southern of Ecuador were used as sensitizers for making dye-sensitized solar cells (DSSCs). The effect of type and amount of material, type and time of maceration were tested in order to determine the best conditions of extraction. The extraction of the natural dye was made with acidified ethanol. The sensitizing agents were adsorbed on TiO2 nanoparticles in small solar cells. The DSSCs made with natural dyes from extracts of blackberry (Rubus glaucus B), mortiño (Solanum americanum Mill), escancel (Iresine herbstii Hook) and beet (Beta vulgaris L) developed an open-circuit tension (Voc) 0.65, 0.5, 0.45 and 0.19 V, respectively. The short-circuit currents (Isc) varies from 2.05 to 19.68 mA cm-2 and the fill factor ranging from 0.61 to 0.69. The DSSCs sensitized with the extract of Rubus glaucus B offered the highest maximum power of 8.83 mW. Thus, the natural dyes used showed great potential as sensitizers in DSSCs, besides being environmentally friendly and their low cost.

The aim of this study was to compare the usefulness of three extraction methods: solid-phase microextraction (SPME) with four different coating (PDMS, PDMS/DVB, DVB/CAR/PDMS and PA), supercritical fluid extraction with carbon dioxide (SCF) and simultaneous distillation and extraction (SDE) for isolation of flavor compounds from roasted ground coffee (Coffea arabica L. var. Typica) of Vilcabamba (Ecuador). Identification and characterization of volatile compounds were achieved using gas chromatography / mass spectrometry (GC-MS). Analysis of variance and principal components analysis was done. For the SPME method the coating material affect the amount and concentration of compounds extracted, the DVB/CAR/PDMS coating provided the most representative aroma extract (44 compounds were identified). The SCF method allowed extracting a higher amount of compounds and also their identification by GC-MS (72) that SDE (64) and SPME (57), in addition provide higher extractions. The acetic acid, caffeine, furfuryl alcohol, furfural, 5-methylfurfural, butylated hydroxytoluene and maltol were the compounds with higher concentrations found with SPME and SDE, with SCF were found higher concentration to compounds with high molecular weights (> 194 g mol-1). Preferably SPME-DVB/CAR/PDMS method should be used for a characterization of coffee aroma compounds.