Novel and miniaturized technique, a dynamic sonication-assisted solvent extraction before the analysis by high performance liquid chromatography-ultraviolet visible (HPLC-UV-Vis) for isolation, identification and quantification of rutin and quercetin metabolites in alcoholic extracts from Bidens pilosa Linné, was developed. The results showed that the flowers have a greater quantity of both analytes than other parts of the plant (e.g., leaves, stem and roots), the results were corroborated by liquid chromatography-mass spectrometry (LC-MS). In addition, the developed extraction technique against traditional methods for metabolites extraction such as solid-liquid extraction, Soxhlet and rotating-disk sorptive extraction was compared. Under optimal conditions of extraction such as 0.3 mL min-1 of solvent flow, ethanol:water (1:1) as solvent type and 0.5 g of sample amount, it was possible to reach 85% of recovery percentage of target analytes and a limit of detection close to 0.1 µg g-1 with a linear range of 50-400 µg g-1 were also obtained. Finally, the antibacterial evaluation of the flower extract of Bidens pilosa Linné, obtained under above optimal conditions against Gram-positive bacteria, was performed. The higher values of the inhibition diameters when using 1000 mg L-1 and significant differences among Staphylococcus aureus, Bacillus cereus, and Listeria monocytogenes were observed. The tests were performed with different microorganisms inoculated from three different absorbance levels (0.05, 0.5 and 0.1 absorbances), at a lower absorbance of these microorganisms in the growth medium used for evaluating the inhibitory effect of the B. pilosa Linné extract, when using this extract at the concentrations of 500 and 1000 mg L-1, statistically higher inhibition diameters were noticed.

The main goal consisted in the characterization of gradual concepts according to the categories of physical and chemical processes. The first step was to identify preceding notions about this principle of interaction in daily happenings, followed by the implementation of didactic interventions in order to appropriate the concept, and, finally, the determination of better acceptance of mental representations. This proposal has promoted the comprehension of the universe at macroscopic and microscopic levels and fosters constructive attitudes towards the study of science. This study is based on the corpuscular theory of matter and its interaction with light as a form of energy. The approach is based on a qualitative methodology with a comprehensive - descriptive perspective. A group of twenty-two students was analyzed at a generalized level in the mentioned categories and also, an insightful analysis of three learners with the purpose of determining changes in their cognitive representations. Paralleling the initial test with the final one, it was established that 31.8% of the pupils is placed on the physical - process category, 63.6% on the chemical - process category, and only 4.5% of them does not indicate the interaction; this evidences the progressive conceptual change and the gradual distancing of previous ideas.

Aflatoxins are toxic metabolites produced by Aspergillus species in raw materials and foodstuffs from agricultural sources. Due to the fact that aflatoxins are potentially carcinogenetic, it is important to have reliable analytic methods that allow determining their levels in food matrices. The main aim of this investigation was to validate the method for aflatoxins determination by high performance liquid chromatography in corn arepas, which are widely consumed in the Colombian coffee region. The evaluated parameters were robustness, selectivity, linearity, sensitivity, repeatability, intermediate precision and recovery. The methodology was successfully validated with and optimal selectivity, linearity > 0.9998, limits of detection and quantification lower than 0.10 μg kg−1, relative standard deviation < 4.5% and recovery > 76.6%. Also, 144 corn arepas samples were analyzed and aflatoxins were found in 9.72% of them, with levels between 0.95 and 11.56 μg kg−1.

En este estudio se realizó la validación de los métodos establecidos por la UNODC para la cuantificación y extracción de benzometilecgonina (cocaína) presente en las hojas de Erythhroxylum coca, en té de coca y en clorhidrato de cocaína. El primer método de extracción, recomendado por la UNODC, es una extracción solido-líquido (ESL), sin embargo, los resultados obtenidos indican que esta no es lo suficientemente eficiente para lograr una señal de analito distinguible de la relación señal a ruido (S/N) para las muestras de hojas de Erythhroxylum coca y té de coca. El segundo método propuesto es la extracción soxhlet, los resultados indican que esta resulta más eficiente para aislar y cuantificar el analito de interés por cromatografía de gases acoplada a un detector de ionización por llama (CG-FID). Después de someter las muestras al proceso de extracción soxhlet y cuantificación por CG-FID se encontró que la hoja de té posee 7,66×10² mg de cocaína/kg de muestra, las hojas de coca 17,15 mg de cocaína/kg de muestra y el clorhidrato de cocaína 7,15×10(5) mg de cocaína/kg de muestra. El método de análisis escogido se caracteriza por arrojar bajos límites de detección (0,169 mg/L) y por poseer parámetros estadísticos y cromatográficos ideales.

In this study validate the methods established by the UNODC for quantification and extraction benzometilecgonina (cocaine) in the leaves of Erythhroxylum coca, coca tea and cocaine hydrochloride. The first extraction method recommended by the UNODC is a solid-liquid extraction (ESL), however, the results indicate that this is not efficient enough to achieve analyte signal distinguishable from the signal to noise ratio (S/N) for samples Erythhroxylum coca leaves and coca tea. The second proposed method is soxhlet extraction, the results indicate that this is more efficient to isolate and quantify the analyte of interest by gas chromatography coupled to a flame ionization detector (GC-FID). After submitting the samples to the soxhlet extraction process and quantification by GC-FID it found that tea leaf has 7.66×10² mg of cocaine/kg sample, coca leaves 17.15 mg of cocaine/kg sample and cocaine hydrochloride concentration corresponded to 7.15×10(5) mg of cocaine/kg sample. The chosen analysis method is characterized by low detection limits shed (1.69 mg/L) and possessing ideal chromatographic and statistical parameters.

Neste estudo validaram-se os métodos estabelecidos pelo UNODC para a quantificação e extração de benzometilecgonina (cocaína) nas folhas de Erythhroxylum coca; em chá de coca e cloridrato de cocaína. O primeiro método de extração recomendado por UNODC é uma extração sólido-líquido (ESL), no entanto, os resultados indicam que esta não é suficientemente eficaz para atingir um sinal de analito distinguível da relação sinal-ruído (S/N) para amostras de folhas Erythhroxylum coca e chá de coca. O segundo método proposto é uma extração soxhlet, os resultados indicam que este é mais eficiente para isolar e quantificar o analito de interesse por cromatografia gasosa acoplada a um detector de ionização de chama (GC-FID). Depois de enviar as amostras para o processo de extração soxhlet e quantificação por GC-FID descobriu-se que as folhas de chá têm 7,66×10² mg de cocaína/kg de amostra, as folhas de coca 17,15 mg de cocaína/kg de amostra e o cloridrato de cocaína 7,15×10(5) mg de cocaína/kg de amostra. O método de análise escolhido é caracterizado por ter baixos limites de detecção (1,69 mg/L) e possuir parâmetros estatísticos e cromatográficos ideais.

Neste trabalho são descritos os resultados da otimização da técnica de microextração em fase sólida acoplada ao headspace e detecção por cromatografia gasosa com detector de microcaptura de elétrons (HS-SPME/GC-µECD). A melhor condição de extração para os quatro trihalometanos em água potável foi conseguida através de um estudo da metodologia de superfície de resposta, usando um planejamento fatorial composto 2(5). Cinco variáveis influentes tais como o tipo de fibra, temperatura de extração e de dessorção e tempo de extração e de dessorção foram avaliadas. As variávies que exerceram maior influência na técnica HS-SPME foram a temperatura de extração e os tempos de dessorção e extração. O tipo de fibra e a temperatura de dessorção foram menos influentes na eficiência da extração. As melhores condições de extração foram obtidas quando empregou-se a fibra de carboxeno / polidimetilsiloxano (CAR/PDMS) de 75 µm, temperatura de dessorção 250 ºC, de extração 37,5 ºC, tempo de extração 30 min e de dessorção 4 min.

In this work the results of the optimization of headspace solid phase microextraction technique and determination by gas chromatography with micro electron capture detector (HS-SPME/GC-µECD) are described. The best condition of extraction for the four trihalomethanes in drinking water was reached through a response surface methodology's study using a composite 2(5) factorial design. Five experimental conditions of influence such as the type of fiber, extraction and desorption temperatures and extraction and desorption times were evaluated. The most influential factors in the technique of HS-SPME were the extraction temperature and extraction and desorption times. The type of fiber and the desorption temperature had little influence on extraction's efficiency. The best conditions were obtained with a fiber carboxen/polidimetilsiloxane (CAR/PDMS) of 75 µm, desorption temperature 250 ºC, extraction temperature 37.5 ºC, extraction time 30 min and a desorption time 4 min.

Este trabajo muestra los aspectos más relevantes relacionados con la primera caracterización química de la materia orgánica natural del río Pasto. Para este propósito fue necesario el uso de técnicas de análisis instrumental moderno tales como la: Termoquimólisis-CG-MS, Cromatografía de fraccionamiento en flujo mediante campos; plasma acoplado inductivamente acoplado a espectrometría de masas ICP-MS. Los resultados muestran que los principales componentes de esta materia fueron compuestos orgánicos tales como ácidos carboxílicos, compuestos aromáticos con pesos moleculares alrededor de 5 kDa. La presencia de hierro y cromo son signos de una posible contribución de suelos volcánicos del área ricos en pirita y algunos efluentes descargados sin control de la pequeña industria artesanal del cuero respectivamente.

This work shows the more relevant issue related with the first chemical caracterization of natural organic matter of Pasto River. Modern instrumental analysis techniques such as Thermochemolysis-GC-MS; Field flow fractionation chromatography and Inductively coupled plasma mass spectrometry ICP-MS were necessary. The results showed that the main composition of this matter were organic compounds such as carboxylic acids, aromatic compounds with molecular mass around 5 kDa The presence of iron and chromium ions are signs of a possible contribution of pyrite-rich volcanic soils of the area and some effluent discharged without control of the small artesanal leather industry respectively.

La técnica de análisis por combustión y detección por infrarrojo no dispersivo (IRND) fue validada para la determinación de materia orgánica en agua, cuantificada como carbono orgánico total (COT). Previamente se optimizó la eliminación del carbono inorgánico (CI) de la muestra con un tiempo óptimo de 1,5 min y una relación ácido de 5%. Se estableció un rango dinámico lineal (RDL) entre 3 y 20 mg/L de COT, en el cual la recta de regresión cumplió con los parámetros que acreditaron su linealidad según el análisis por el método de los mínimos cuadrados, mostrando un coeficiente de correlación de 0,9994. La sensibilidad expresada por la pendiente de la recta de regresión indicó una variación de aproximadamente 5 unidades en la respuesta del detector por cada mg/L de COT. Los límites de detección y cuantificación obtenidos a partir de la recta de regresión fueron 0,517 y 1,722 mg/L de COT, respectivamente. La precisión de la técnica, teniendo como meta un 5% en coeficiente de variación (CV), fue mejor en el agua potable y en concentraciones cercanas a ésta (aprox. 7 mg/L de COT), mientras que las mayores desviaciones se presentaron en concentraciones cercanas a los límites inferior y superior del RDL. Las recuperaciones de concentraciones conocidas sobre muestras reales adicionadas fueron del 85% con baja adición y del 83% con adición alta, valores que sugieren una reevaluación del desempeño de la técnica con respecto a su exactitud, no obstante se alcanzó la meta de recuperación comprendida entre el 70 y el 130%. La técnica así establecida es por tanto apta para el análisis de aguas crudas, potables y residuales y es viable su utilización en el seguimiento a procesos de oxidación avanzada aplicados en el tratamiento de agua para consumo humano.

The technique of combustion analysis and detection by non-dispersive infrared (NDIR) was validated for the determination of organic matter in water, quantified as total organic carbon (TOC). Previously optimized the elimination of inorganic carbon (IC) of the sample with an optimum time sparge of 1.5 min and an acid ratio of 5%. It established a linear dynamic range (LDR) between 3 and 20 mg/L of TOC, in which the regression line that met the parameters credited its linearity as analyzed by the method of least squares, showing a correlation coefficient of 0,9994. The sensitivity expressed by the slope of the regression line indicated a variation of about 5 units in the detector response for each mg/L of TOC. The detection and quantification limits obtained from the regression line were 0.517 and 1.722 mg/L of TOC, respectively. The precision of the technique, aiming at 5% coefficient of variation (CV) was better in the drinking water at concentrations close to it (about 7 mg/L of TOC), whereas larger deviations were presented at concentrations near the lower and upper limits of LDR. The recoveries of known concentrations of actual samples of 85% additions were low addition and 83% with high added values that suggest a reevaluation of the performance of the technique with respect to its accuracy, however the goal was reached between recovery 70 to 130%. The technique is well established thereby capable of analyzing raw water, drinking and waste and feasible to use in monitoring advanced oxidation processes applied in the treatment of drinking water.