Aplicaciones del uso de la técnica de espectroscopía de reflectancia difusa en química forense para la carcterización de autenticidad de los sellos de correos de España

Dentro del área de las Ciencias Forenses, la Documentoscopia es una de sus secciones más atractivas. Tan atractiva como es la Filatelia, el coleccionismo de efectos postales, en el mundo moderno. La Espectroscopía de Reflectancia Difusa, debido a tener como principal característica el ser una técnica no destructiva y de fácil manejo, puede ser una herramienta de gran valor para el estudio de la autenticidad de piezas filatélicas. En este trabajo, presentamos un análisis cualitativo de varios sellos antiguos españoles procedentes de diferentes emisiones desde el reinado de Isabel II hasta Alfonso XIII, profundizando en la Serie del Gobierno Provisional de 1870 -caracterizada por la profusión…

Estudios químico-analíticos para la determinación de Biguanidas en preparados farmacéuticos

Extractive-spectrophotometric determination of amphetamine in urine samples with sodium 1,2-naphthoquinone 4-sulphonate

Abstract Sodium 1,2-naphthoquinone 4-sulphonate (NQS) was tested as a reagent for amphetamine in order to develop an extractive-spectrophotometric method for the drug in urine samples. The standard additions method showed the absence of proportional bias error whereas the Youden method and the two standard addition plots method showed the presence of a constant bias error [total Youden blank (TYB)]. Acceptable results were obtained by evaluating the TYB error or by using a placebo (urine sample from a normal subject). The dynamic range of concentrations was 1.4–50 mg 1−1 in urine samples and the detection limit was 0.6 mg 1−1 when 10 ml of urine sample were taken.

Spectrophotometric analysis of mixtures of two components with extensively or completely overlapping spectra by the H-point standard additions method

This paper discusses the requirements and scope of application of the H-Point Standard Additions Method (HPSAM) for resolving binary mixtures. Various mixtures of dyes with extensively or completely overlapping spectra were assayed with accurate, precise results. The method thus developed was also applied to the spectrophotometric resolution of binary mixtures of phenol and o-cresol, the absorption bands of which lie in similar positions and feature similar absorptivities.

Interpretation and Chemometric Evaluation of the Bilirubin Interference in the Kinetic Spectrophotometry Determination of Creatinine in Serum by Use of the Jaffe Reaction

Abstract SUMMARY In an alkaline picrate medium we demonstrated the occurrence of isosbestic points over the range 520–550 nm, the position depending on the bilirubin content and less on the albumin content. Bilirubin does not markedly modify the ratt constant of the reaction between creatinine and picrate, however, it does modify the intercept of the Ln ΔA vs t, plots. The absolute value of Ln ΔA varies with the concentration, though not with time, which indicates that bilirubin acts by consuming part of the initially present creatinine irrespective of its owr concentration at the wavelengths typically used in the creatinine determination. The Ln ΔA values at the isosbestic points coincide …

Comparison of several methods used for the determination of cephalosporins. Analysis of cephalexin in pharmaceutical samples

The precision of UV absorbance of intact and acid degraded cephalosporins, ninhydrin, high performance liquid chromatography and iodometric methods used for analysis of cefoxitin, cefotaxime, cephazolin and cephalexin were compared. To obtain the calibration graphs the analytical signal used were: absorbance, first derivative absorbance, second derivative absorbance and H-point Standard Additions Method by using absorbance values at two selected wavelengths as analytical signal. These methods and calibration graphs were also used for the determination of cephalexin in pharmaceutical samples.

Derivatization of amphetamine and methamphetamine with 1,2-naphthoquinone 4-sulfonic acid into solid-phase extraction cartridges. Determination of amphetamine in pharmaceutical and urine samples.

The derivatization of amphetamine and methamphetamine with 1,2-naphthoquinone-4-sulfonate (NQS) into solid-phase extraction cartridges (C 18 ) is described. Optimum conditions were the use of carbonate–hydrogencarbonate buffer of pH 10, a 10 min reaction time at 25 °C and an NQS concentration of 9.6 × 10 - 3 M. The accuracy and the precision of the method were tested. The results obtained with the proposed liquid–solid procedure were compared with those obtained with a traditional liquid–liquid extraction with hexane–ethyl acetate. The procedure was used to measure amphetamine in pharmaceutical and urine samples

Life after death: a physicochemical study of materials used by the ancient Maya in human bone ointments

Ancient Maya believed in life after death. They used to prepare dead bodies during burial ceremonies whose purpose was to celebrate the dead and to help them passing through the way from earthly life to the beyond one. Bodies preparation included coloured scented body ointment application, with a deep symbolic connotation and probably also a conservative purpose. The aim of this research was to characterize pigments and binders used by ancient Maya in the preparation of body oint ments used to paint human bones. Emblematic painted bone samples from Xcambó (Maya archaeological site located in the municipality of Dzemul, in the Mexican state of Yucatán) were investigated through a non-destruc…

Application of the H-point standard additions method by using absorbance increment values as analytical signals

Abstract This paper demonstrates how the absorbance increment (ΔA) between two wavelengths selected according to the fundamental criteria for application of the H-Point standard additions method (HPSAM) are only related to the analyte concentration. A procedure for calculation of the unknown analyte concentration with no bias error by applying HPSAM to ΔA values in much the same way as the method of standard additions (MOSA), is reported. The method was also applied to a calibration with a single standard. The results obtained on 6 samples with maximal separations between 65 and 0 nm are reported. Finally, the proposed method was applied to the resolution of different phenol-o-cresol mixtur…

Prevenció de riscs laborals en el laboratori de química analítica (PRLQA)

Es tracta de la web que recopila les activitats dels membres del gid relacionades amb temes docents pel que s’inclouen vídeos, qüestionaris, comunicacions a congressos i publicacions. Se trata de la web que recopila las actividades de los miembros del grupo de innovación docente relacionadas con temas docentes por lo que se incluyen videos, cuestionarios, comunicaciones a congresos y publicaciones. The web reports the results of gid members related to educational activity. The web includes videos, questionnaires, congress communications and publications.

Desarrollo de material multimedia para la prevención de riesgos en el laboratorio docente de Química Analítica. Primera parte: Normas básicas en el laboratorio de Química Analítica.

El material consta de un video y un cuestionario. El video contiene información básica sobre las normas de trabajo en el laboratorio de Química Analítica. Se abordan los aspectos generales sobre el trabajo seguro en un laboratorio, los elementos de seguridad del laboratorio, los equipos de protección tanto individual como colectivos, las normas de etiquetado y manipulación de productos químicos, y los riesgos asociados a la manipulación de material e instrumentación básica del laboratorio. Finalmente, el cuestionario contiene diversas preguntas relativas a los aspectos de seguridad e higiene industrial mostrados en el vídeo. El material consta d'un vídeo i un qüestionari. El vídeo conté inf…

Desarrollo de material multimedia para la prevención de riesgos en el laboratorio docente de Química Analítica. Segunda parte: Laboratorio de Instrumentación.

El material consta de un video y un cuestionario. El video contiene información básica sobre la prevención y riesgos que conlleva la utilización y manejo de instrumentación en los laboratorios de Química Analítica. Se abordan los aspectos generales sobre el trabajo seguro en un laboratorio de instrumentación analítica, así como los riesgos específicos de las principales técnicas analíticas: espectroscopia molecular, espectroscopia atómica, métodos eléctricos y métodos cromatográficos. Finalmente, el cuestionario contiene diversas preguntas relacionadas con las conductas de trabajo adecuadas para la prevención de riesgos en el laboratorio de instrumentación analítica. El material consta d'un…