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 de los variados colores encontrados a lo largo de los 13 valores que componen la serie completa-, e incluso estudiando efectos auténticos frente a otros ejemplares falsos indubitadosIn the area of forensic sciences, the questioned document examination is one of its most attractive sections. As attractive as philately, the collecting of postal effects, in the modern world. Diffuse reflectance spectroscopy, due to have as main characteristic being a technique of non-destructive and easy to use, can be a tool of great value to the study of the philatelic pieces authenticity. In this work, using Diffuse Reflectance Spectroscopy, we present qualitative analysis of several early Spanish stamps issued from different emissions since the reign of Queen Isabel II to King Alfonso XIII, deepening over the series of the Provisional Government issued in 1870 - characterized by the profusion of variations of the colors found among the 13 values that compose the complete series-, and even studying authentic effects against other counterfeit recognized as fake copies

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-destructive and micro-destructive analytical techniques. Results pointed out the presence of two mainly red pigments, i.e. red ochre and cinnabar, as already observed in other Maya painted bones. The new insight of the research is the identifcation of the organic compounds used as binding media in the ointments: a mixture of vegetable drying oil (probably Chia seed oil) mixed with an aromatic compound (bitumen). This knowledge, together with that obtained in the last decades, is important to reconstruct the cultural habitat and social customs of this pre-Hispanic civilization and transfer them to today's contex

A new tool for evaluating and/or selecting analytical methods: Summarizing the information in a hexagon

[EN] A quantitative evaluation tool is proposed, which aims to assess optimal selection or/and testing of analytical methods. Objective criteria related to analytical performance, sustainability, environmental impact and economic cost are evaluated through the definition of penalty points divided into five different blocks, namely, figures of merit, toxicity and safety, residues, carbon footprint and economic cost. For each block, the overall qualification is scaled from 0 to 4 and it is depicted on a regular hexagonal pictogram that allows a user friendly comparison of analytical procedures. The present evaluation tool aims to be a guideline for evaluating and/or selecting analytical procedures that are in line with Green Chemistry philosophy, but also balancing the figures of merit needed for solving a given problem, safety and cost-effectiveness. Real examples have been tested

NQS-Doped PDMS Solid Sensor: From Water Matrix to Urine Enzymatic Application

[EN] The development of in situ analytical devices has gained outstanding scientific interest. A solid sensing membrane composed of 1,2-naphthoquinone-4-sulfonate (NQS) derivatizing reagent embedded into a polymeric polydimethylsiloxane (PDMS) composite was proposed for in situ ammonium (NH4+) and urea (NH2CONH2) analysis in water and urine samples, respectively. Satisfactory strategies were also applied for urease-catalyzed hydrolysis of urea, either in solution or glass-supported urease immobilization. Using diffuse reflectance measurements combined with digital image processing of color intensity (RGB coordinates), qualitative and quantitative analyte detection was assessed after the colorimetric reaction took place inside the sensing membrane. A suitable linear relationship was found between the sensor response and analyte concentration, and the results were validated by a thymol-PDMS-based sensor based on the Berthelot reaction. The suggested sensing device offers advantages such as rapidity, versatility, portability, and employment of non-toxic reagents that facilitate in situ analysis in an energy-efficient manner

Rapid evaluation of ammonium in different rain events minimizing needed volume by a cost-effective and sustainable PDMS supported solid sensor

[EN] The presence of ammonium ion in rainwater is due to atmospheric processes which involve its scavenging from gas phase and particulate matter. The fractionated samplings of rainwater can provide information about these processes and their potential sources. However, only a low sample volume may be available, which constrained the analysis in general and more particularly in situ mode. For minimizing this limitation, this work proposes a polydimethylsiloxane (PDMS)-salicylate sensor that produces a color change. The embedding of solid reagents into PDMS was optimized. Good analytical characteristics (analysis time of 10 min, sample volume of 500 mL, limit of detection 0.03 mg/mL1) were obtained. Furthermore, other features of the method such as carbon footprint, equipment cost, residues, toxicity and safety have to be taken into account to be assessed according to the Green Analytical Chemistry approach. In this sense, the hexagon tool was employed for comparing the proposed sensor with methods based on the same reaction as well as with general methods for the ammonium analysis in water (using luminol, ion selective electrode, Nessler and modified Roth method). The proposed method based on PDMS-salicylate sensor stands out from all the others by its sustainability, particularly, in terms of low carbon footprint, residues and cost. The method was applied to fractionated samplings in a suburban site (Galicia, Northwestern Spain) and a higher contribution of the rainout process was observed. When long-duration rain events were analyzed, a relationship between the sampling time and ammonium concentration could indicate a loss of ammonium ion over time. The research focuses on developing an innovative PDMS-sensor, for monitoring ammonium determination in rainwater under wide conditions (scavenging process)

Color study of historic silks

The chemical characterization of silk textiles of historic value may be necessary to achieve a better understanding of the production processes applied, to evaluate their preservation, to detect manipulations or forgeries, and to value the combination of tradition and innovation in contemporary manufacturing techniques. The main objective of this work was to study four historical silks from the Garín collection, all of them from the 20th century, although with 19th century designs. To this end, non-invasive spectroscopic and microscopy techniques were applied in order to obtain information on the dyes used during their production and their link with those used in the silk industry in previous centuries, and to ascertain their state of conservation. Moreover, the images in LM, SEM and CM are contributing to the development of a 3D virtual loom that will favor more accessible and inclusive museography in museums specialized in the silk sector. Both the study of dyes and silk fibers and their virtual reproduction through artificial intelligence programs applied to the study of cultural heritage, by specialists from the Robotics Institute of the Universitat de València, has been developed in the framework of the SILKNOW project (https://silknow.eu/)

Peptide Metal-Organic Frameworks for Enantioselective Separation of Chiral Drugs

We report the ability of a chiral Cu(II) 3D MOF based on the tripeptide Gly-L-His-Gly (GHG) for the enantioselective separation of metamphetamine and ephedrine. Monte Carlo simulations suggest that chiral recognition is linked to preferential binding of one of the enantiomers as result of either stronger or additional H-bonds with the framework that lead to energetically more stable diastereomeric adducts. Solid phase extraction (SPE) of a racemic mixture by using Cu(GHG) as extractive phase permits isolating more than 50% of the (+)-ephedrine enantiomer as target compound in only four minutes. To the best of our knowledge, this represents the first example of a MOF capable of separating chiral polar drugs

Reduction of Nitrates in waste water through the valorization of rice straw: LIFE LIBERNITRATE Project

An improved and more sustainable waste management system is required for successful development of technologies based on renewable sources. Rice straw is submitted to controlled combustion reactions and the produced ashes are chemically treated to produce silica. After a chemical activation step, the activated silica shows potential as an adsorbent agent and will be used to remove the excess of nitrates in groundwater and wells in the area of Alginet (Valencia, Spain), selected as a vulnerable zone within the Nitrates Directive. The demonstration activity aims to have a local impact on municipalities of 200 inhabitants or fewer, decreasing from current nitrate concentrations close to 50 mg/L, to a target of 25 mg/L. In a successive step, the methodology will be transferred to other municipalities with similar nitrate problems (Piemonte, Italy) and replicated to remove different pollutants such as manure (the Netherlands) and waste waters from the textile industry (Italy)

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 vídeo i un qüestionari. El vídeo conté informació bàsica sobre la prevenció i riscs que comporta la utilització i manipulació d'instrumentació als laboratoris de Química Analítica. S'aborden els aspectes generals sobre el treball segur en un laboratori d'instrumentació analítica, així com els riscs específics de les principals tècniques analítiques: espectroscòpia molecular, espectroscòpia atòmica, mètodes elèctrics i mètodes cromatogràfics. Finalment, el qüestionari conté diverses preguntes relacionades amb les conductes de treball adequades per a la prevenció de riscs al laboratori d'instrumentació analítica.This material consisted in one video and questionnaire. The video contains basic information over the prevention and risks in the use of instrumentation in the Analytical Chemistry laboratories. The main topics related with the safe work in the instrumentation laboratory, and the specific risks of the principal analytic techniques (spectroscopic, electrochemical and chromatographic techniques) are showed. Finally, the questionnaire includes several questions related with the good practices in the laboratory of Analytical Chemistry