Carbon isotope ratio of organic acids in sake and wine by solid-phase extraction combined with LC/IRMS.

We developed an analytical procedure for determining the δ13C values of organic acids in sake and wine using solid-phase extraction combined with liquid chromatography/isotope ratio mass spectrometry (LC/IRMS). First, the solid-phase extraction (SPE) procedure was performed and various tests were conducted to extract organic acids from alcoholic beverages using the simulated sake sample. Under the optimal SPE procedure, high recovery rates (96-118%) and good accuracies (≤ 0.7‰) were thus achieved for the simulated sake and wine samples. Next, we determined the δ13C of organic acid (tartaric acid, malic acid, lactic acid, succinic acid) in 9 sake and 11 wine samples. Finally, the δ13C values of lactic acid in nine sake samples suggested that lactic acid had been added during the brewing process. The high correlation between the δ13C values of tartaric acid and malic acid in 11 wine samples was consistent with their common source, grapes. This analytical method may help to identify when organic acids have been added to sake and wine and to elucidate the process of organic acid production therein. Graphical abstract.

Development of a Dye-Based Device to Assess Poultry Meat Spoilage. Part I: Building and Testing the Sensitive Array.

The rationale behind the material and dye selection and the investigation of the properties of a solid-phase sensor array designed for following chicken meat spoilage is presented, having in mind that the final target must be the naked eye identification of the degradation steps. The device is obtained by fixing five acid-base indicators, m-cresol purple (1), o-cresol red (2), bromothymol blue (3), thymol blue (4), and chlorophenol red (5), and a sensing molecule specific for thiols, 5,5'-dithiobis(2-nitrodibenzoic acid), called Ellman's reagent, (6) on a commercial cellulose-based support. The dimensions of the sensor and the amount of dye sorbed on the solid are carefully studied. The preparation protocol to get reproducible sensing materials is established, based on the kinetic study and the color change investigation. The material stability and the capacity of changing color, according to the acid-base properties of the dyes, are tested. The sources of uncertainty, coming from the technique employed for signal data acquisition and treatment and from the intrinsic variability of the spots based on the commercial support, are established. The highest variability does not come from photo acquisition by a mobile phone, the effect of the illumination equipment, the partial least-squares (PLS) model employed to assess the amount of dye sorbed into the solid but from the variability of different spots and was found equal to 10%. The uncertainty is adequate for final employment since it is referred to as replicates under different conditions that are definitively judged almost always identical by naked eye evaluation, which is our last target for assessing a change of the colors associated with spoilage.

Development of a Dye-Based Device to Assess the Poultry Meat Spoilage. Part II: Array on Act.

This work presents a colorimetric dye-based array for naked-eye detection of chicken meat spoilage. The array is obtained by fixing five acid-base indicators, m-cresol purple (1), o-cresol red (2), bromothymol blue (3), thymol blue (4), and chlorophenol red (5), and a sensing molecule specific for thiols, 5,5'-dithiobis(2-nitrodibenzoic acid), called Ellman's reagent (6), on a cellulose-based support. The dyes, being permanently charged, are fixed on the support via ion-exchange. The entire degradation process of beast poultry meat, at ambient temperature and in a domestic fridge, is followed by the change of the color of the array, placed in the headspace over the meat samples. The device is set after selection of the most suitable starting form, which could be the acidic or the basic color of indicators, being the proper dye concentration and the dimension of the spots already established. Basing on sensors colors, we identified three levels of the degradation process of chicken meat, named SAFE, WARNING, and HAZARD. By instrumental analysis, we demonstrated that sensors response was correlated to volatile organic compounds (VOCs) composition in the headspace and, thus, to meat spoilage progress. We demonstrated that biogenic amines (BAs), commonly considered a critical spoilage marker, are indeed produced into the samples but never present in the headspace, even in traces, during the investigated time-lapse. The VOC evolution nevertheless allows one to assign the sample as WARNING and further HAZARD. Some indicators turned out to be more informative than others, and the best candidates for a future industrial application resulted in a bromothymol blue (3)-, chlorophenol red (5)-, and Ellman's reagent (6)-based array.

Evaluación del Agar Azul Bromotimol Lactosa introducido en BioCen con cepas de referencia / Assessment of Agar Blue Bromotimol Lactose introduced in BioCen using reference strans

Exponer los resultados obtenidos en las evaluaciones realizadas a los medios de cultivo Agar azul bromotimol lactosa producido en BioCen, Cuba, y el comercializado por la Merck, Alemania, destinado para la diferenciación de microorganismos especialmente las enterobacterias, por su capacidad de fermentar la lactosa. Se ensayaron un total de 13 cepas certificadas y una aislada de muestra de agua, pertenecientes al Departamento de Investigaciones de Medios de Cultivo (BioCen). Las cepas evaluadas en ambos productos mostraron similitud en cuanto a su respuesta y a las características morfológicas de las colonias. Los valores del índice relativo de crecimiento (IRC) para 10 cepas superaron el 90 por ciento, resultando el 71,5 por ciento del total, mientras que solo 4 cepas reflejaron valores inferiores, resultando el 28,5 por ciento del total. Todas las cepas sobrepasaron el valor recomendado (> 70 por ciento), además las características culturales desarrolladas respondían a las reportadas. Los resultados alcanzados en la determinación del IRC demuestran la buena calidad del medio producido en BioCen frente a cepas de referencia, tomando como criterio el hecho de que todos los microorganismos ensayados mostraron valores del IRC superiores al valor recomendado(AU)

To show results obtained in evaluations performed in agar blue bromotimol lactose culture media produced in BioCen, Cuba, and that marketed by Merck, Germany, created for microorganism differentiation, specially the Enterobacter ones, due to its ability for lactose fermentation. We assayed a total of 13 certified strains and another isolated from water sample, from Research Department of Culture Media (BeioCen). Values or Growing Relative Index for 10 strains were above 90 percent, with 71,5 percent of total, while that only 4 strains shoed lower values to a 28,5 percent of total. All strains exceeded the recommended value (>70 percent). Strains evaluated in both products showed similarity as regard its response and to morphologic features of colonies(AU)

Evaluación del Agar Azul Bromotimol Lactosa introducido en BioCen con cepas de referencia / Assessment of Agar Blue Bromotimol Lactose introduced in BioCen using reference strans

Exponer los resultados obtenidos en las evaluaciones realizadas a los medios de cultivo Agar azul bromotimol lactosa producido en BioCen, Cuba, y el comercializado por la Merck, Alemania, destinado para la diferenciación de microorganismos especialmente las enterobacterias, por su capacidad de fermentar la lactosa. Se ensayaron un total de 13 cepas certificadas y una aislada de muestra de agua, pertenecientes al Departamento de Investigaciones de Medios de Cultivo (BioCen). Las cepas evaluadas en ambos productos mostraron similitud en cuanto a su respuesta y a las características morfológicas de las colonias. Los valores del índice relativo de crecimiento (IRC) para 10 cepas superaron el 90 por ciento, resultando el 71,5 por ciento del total, mientras que solo 4 cepas reflejaron valores inferiores, resultando el 28,5 por ciento del total. Todas las cepas sobrepasaron el valor recomendado (> 70 por ciento), además las características culturales desarrolladas respondían a las reportadas. Los resultados alcanzados en la determinación del IRC demuestran la buena calidad del medio producido en BioCen frente a cepas de referencia, tomando como criterio el hecho de que todos los microorganismos ensayados mostraron valores del IRC superiores al valor recomendado.

To show results obtained in evaluations performed in agar blue bromotimol lactose culture media produced in BioCen, Cuba, and that marketed by Merck, Germany, created for microorganism differentiation, specially the Enterobacter ones, due to its ability for lactose fermentation. We assayed a total of 13 certified strains and another isolated from water sample, from Research Department of Culture Media (BeioCen). Values or Growing Relative Index for 10 strains were above 90 percent, with 71,5 percent of total, while that only 4 strains shoed lower values to a 28,5 percent of total. All strains exceeded the recommended value (>70 percent). Strains evaluated in both products showed similarity as regard its response and to morphologic features of colonies.

Extractive spectrophotometric methods for determination of zolmitriptan in tablets.

Two simple and sensitive extractive spectrophotometric methods have been developed for determination of zolmitriptan (ZTP) in tablets. These methods are based on the formation of yellow ion-pair complexes between ZTP and tropaeolin OO (TPOO) and bromothymol blue (BTB) in citrate-phosphate buffer of pH 4.0 and 6.0, respectively. The formed complexes were extracted with dichloromethane and measured at 411.5 and 410 nm for TPOO and BTB, respectively. The best conditions of the reactions were studied and optimized. Beer's law was obeyed in the concentration ranges of 2-20 and 1.5-17 microg/mL with molar absorptivities of 1.42 x 10(4) and 1.60 x 10(4) L/mol/cm for the TPOO and BTB methods, respectively. Correlation coefficients were 0.9998 and 0.9999 for TPOO and BTB methods, respectively. Limits of detection of the TPOO and BTB methods were 0.341 and 0.344 microg/mL, respectively, and the limits of quantitation were 1.034 and 1.051 microg/mL, respectively. Sandell's sensitivity and stability constant were also calculated. The proposed methods have been applied successfully for the analysis of the drug in its dosage forms. No interference was observed from excipients present in tablets. Statistical comparison of the results with those obtained by a high-performance liquid chromatography method showed excellent agreement and indicated no significant differences in accuracy and precision.

Spectrophotometric determination of certain antidepressants in pharmaceutical preparations.

Simple and reproducible spectrophotometric methods have been developed for determination of sertraline, fluoxetine, and venlafaxine in pharmaceutical preparations. The methods are based on the reactions between the studied drug substances and ion-pair agents (bromothymol blue, bromocresol green, or bromophenol blue) to produce yellow-colored ion-pair complexes in acidic buffers. After extracting in chloroform, the ion-pair complexes are spectrophotometrically determined at the optimum wavelength. Optimizations of the reaction conditions were carried out. Beer's law was obeyed within the concentration range from 1 to 15 microg/mL. The molar absorptivity, Sandell sensitivity, and detection and quantification limits were also determined. The developed methods were applied successfully for the determination of these drugs in some available commercial preparations. The results were compared statistically with those obtained from reported high-performance liquid chromatography methods.

Integration of polymer waveguides for optical detection in microfabricated chemical analysis systems.

Multimode polymer waveguides and fiber-to-waveguide couplers have been integrated with microfluidic channels by use of a single-mask-step procedure, which ensured self-alignment between the optics and the fluidics and allowed a fabrication and packaging time of only one day. Three fabrication procedures for obtaining hermetically sealed channels were investigated, and the spectrally resolved propagation loss (400-900 nm) of the integrated waveguides was determined for all three procedures. Two chemical absorbance cells with optical path lengths of 100 and 1000 microm were furthermore fabricated and characterized in terms of coupling loss, sensitivity, and limit of detection for measurements of the dye bromothymol blue.

A highly sensitive photometric method for proton release or uptake: difference protometry.

A highly sensitive quantitative method was developed to detect protons released or taken up upon ligand binding. A small change in pH due to proton release or uptake was detected by measuring the difference in the absorbance of a pH indicator upon ligand addition. Owing to the difference detection of protons, the uncertainty of pH due to CO2 dissolution and unknown buffering capacities of sample solutes could be compensated with easy manipulations. Precise calibration of the absolute amount of protons could also be made very easily. The amount of protons measurable by the method is as small as 0.5 nmol that is 10 to 30 times more sensitive than the pH-stat method. We measured the Mg2+ ion-induced proton releases of ADP to confirm the accuracy and reliability of the method and of Escherichia coli ribosomes to show the improvement in sensitivity. The method is useful for protometric studies of biomolecules that are difficult to obtain in large amount.