216 research outputs found
A sustainable and simple energy dispersive X-ray fluorescence method for sulfur determination at trace levels in biodiesel samples via formation of biodiesel spots on a suitable solid support
The aim of the present work is the development of a simple, sensitive and sustainable EDXRF method for the determination of trace amounts of sulfur in biodiesel samples. In this method, the deposition of several microliters of sample onto an organic thin layer and the analysis of the resulting adsorbed biodiesel spot by benchtop EDXRF is proposed. A careful study was performed to select the volume and the best solid support to deposit biodiesel samples, including filters made of different materials (glass fiber, Nylon, cellulose, paper) and a commercial disposable absorbent pad (UltraCarry, Rigaku). A critical issue that limits the use of most of these solid supports was the relative high blank signals that hamper the determination of sulfur at trace levels. Finally, it was found that best strategy was the deposition of 50 ÂľL of biodiesel on the UltraCarry sample retainer. Operating conditions for EDXRF measurements were also evaluated to obtain the best instrumental sensitivity for sulfur determination (Excitation: 20 kV, no primary filter, measurement time: 300 s). Using the best analytical conditions the quantification limit of the method was 7 mg kg -1 of sulfur. This value is even better than the one reported in the ASTM D4294 method (LOQ: 16.0 mg kg -1 ) but using a sample amount 100 times smaller. The linearity was confirmed in the range of 10â100 mg kg -1 by analyzing a set of commercial biodiesel standards. Accuracy and precision of the results, evaluated by the analysis of samples prepared with the same matrix as the standards, with levels of 20, 40 and 75 mg kg -1 of sulfur, and processed as unknowns, proved acceptable (Recoveries: 94.3â110.6%, RSD: 10.8â13.6%, n = 3) for the intended purpose. Overall, the performance of the method developed is promising and it could be used to determine trace amounts of sulfur in biodiesel samples in a simple, sustainable and cost-effective way. Furthermore, since the original sample is adsorbed onto a solid support, repeat confirmatory analyses on the same specimen, if needed, can be carried out
Disseny de sistemes dâalimentaciĂł òptica per a sistemes sensors autònoms
Els sensors autònoms requereixen sistemes dâalimentaciĂł de manteniment mĂnim. En el present projecte per aconseguir-ho sâutilitza lâenergia lumĂnica. Per tal de captar la llum (energia) que provĂŠ del sol (llum natural) i de les lĂ mpades o fluorescents (llum artificial) sâutilitzen celâ˘les solars dissenyades per interiors, les quals tenen la propietat de captar lâenergia òptica i transformar-la en electricitat. Per altra banda sâha realitzat un estudi de com afecten les diferents fonts de llum a les celâ˘les. Dâaquesta manera sâha pogut observar que la celâ˘la tĂŠ millor rendiment com mĂŠs aprop tĂŠ la font lluminosa. TambĂŠ sâhan realitzat mesures dâirradiĂ ncia amb lâespectroradiòmetre i dâilâ˘luminĂ ria amb el luxòmetre tant en interiors com en exteriors. Per aconseguir tenir un sistema autònom, ĂŠs necessari emmagatzemar aquesta energia. Això sâaconsegueix mitjançant lâĂşs de les bateries recarregables i aquesta energia sâutilitza durant els perĂodes en els quals la celâ˘la no rep llum. Sâha comprovat que una celâ˘la ĂŠs capaç de carregar una bateria
Disseny de sistemes dâalimentaciĂł òptica per a sistemes sensors autònoms
Els sensors autònoms requereixen sistemes dâalimentaciĂł de manteniment mĂnim. En el present projecte per aconseguir-ho sâutilitza lâenergia lumĂnica. Per tal de captar la llum (energia) que provĂŠ del sol (llum natural) i de les lĂ mpades o fluorescents (llum artificial) sâutilitzen celâ˘les solars dissenyades per interiors, les quals tenen la propietat de captar lâenergia òptica i transformar-la en electricitat. Per altra banda sâha realitzat un estudi de com afecten les diferents fonts de llum a les celâ˘les. Dâaquesta manera sâha pogut observar que la celâ˘la tĂŠ millor rendiment com mĂŠs aprop tĂŠ la font lluminosa. TambĂŠ sâhan realitzat mesures dâirradiĂ ncia amb lâespectroradiòmetre i dâilâ˘luminĂ ria amb el luxòmetre tant en interiors com en exteriors. Per aconseguir tenir un sistema autònom, ĂŠs necessari emmagatzemar aquesta energia. Això sâaconsegueix mitjançant lâĂşs de les bateries recarregables i aquesta energia sâutilitza durant els perĂodes en els quals la celâ˘la no rep llum. Sâha comprovat que una celâ˘la ĂŠs capaç de carregar una bateria
Ceria nanoparticles deposited on graphene nanosheets for adsorption of copper(II) and lead(II) ions and of anionic species of arsenic and selenium
A nanocomposite prepared from graphene nanosheets and cerium nanoparticles (G/CeO2) was applied to the extraction of
Se(IV), As(V), As(III), Cu(II) and Pb(II). The structure of G/CeO2 was investigated by scanning electron microscopy, X-ray
diffraction and Raman spectroscopy. The optimal pH values for extraction are 4.0 for As(V), 3.0 for Se(IV), and 6.0 for both
Cu(II) and Pb(II). The maximum adsorption capacity of G/CeO2 (expressed as mg¡gâ1) were calculated by the Langmuir model
and are found to be 8.4 for As(V), 14.1 for Se(IV), 50.0 for Cu(II) and 75.6 for Pb(II). The sorbent was applied to dispersive solid
phase microextraction prior to direct quantitation by energy-dispersive X-ray fluorescence spectrometry without the need for
prior elution. The limits of detection (in ng¡mLâ1 units) are 0.10 for As(V), 0.11 for Se(IV), 0.19 for Cu(II) and 0.21 for Pb(II).
The precisions (RSDs) are <4.5%. The accuracy of the method (1 - 4%) was verified by analysis of the certified reference material
(CRM 1640a - natural water). The method was successfully applied in ultratrace element determination and to the speciation of
selenium in environmental waters
La figura del general EstartĂşs
No ens ha de fer estrany que la figura de l'EstartĂşs s'esvaĂs aviat de l'escena polĂtica. Cal tenir present que era un home d'una enteresa total, i que per damunt de carlins i liberals, no s'avinguĂŠ mai a fer el joc als qui mancats d'escrĂşpol i desbordats de concupiscència es desentengueren dels principis que deien defensa ri, sense possibilitat de triomf, guerrejaren en va o per fer el fatxenda
Application of benchtop total-reflection X-ray fluorescence spectrometry and chemometrics in classification of origin and type of Croatian wines
The contents of selected metals (K, Ca, Fe, Cu, Zn, Mn, Sr, Rb, Ba, Pb, Ni, Cr and V) in 70 wine samples from Continental and Adriatic part of Croatia and different types of wine (red and white) were determined by TXRF. The aim of this study was to compare the elemental composition of wines from two different regions and to determine the discriminant ability of each variable and to indicate which variables discriminate between the four categories considered. Principal component analysis and cluster analysis showed that K, Mn, Ba and Ni can be considered as the most important characteristics to distinguish between Continental red and white wines, Rb, Ni and Ba for Continental red and Adriatic red wines while Sr is the only metal that completely distinguishes the samples of each category. Finally, linear discriminant analysis showed good recognition (100%) and prediction abilities (96.43%) using these selected elements
Estudi del comportament de les nanopartĂcules de plata en sòls agrĂcoles
En aquest treball, sâhan dut a terme estudis dâadsorciĂł en discontinu i tests de lixiviaciĂł per a entendre els processos dâadsorciĂł/desorciĂł de les nanopartĂcules de plata (AgNP) en els sòls. Sâha observat que les AgNP presenten una retenciĂł rĂ pida i una mobilitat baixa en els sòls i tenen un paper important la capacitat dâintercanvi catiònic i la conductivitat elèctrica del sòl, aixĂ com la cĂ rrega superficial i la mida de les AgNP. Tres setmanes desprĂŠs dâestar en contacte amb el sòl, la majoria de les AgNP mantenen la seva nanoforma. LâaplicaciĂł de lâextracciĂł en punt de nĂşvol (cloud-point extraction) permet caracteritzar acuradament les AgNP en mostres que contenen plata iònica
Evaluation of different analytical approaches using total reflection X-ray fluorescence systems for multielemental analysis of human tissues with different adipose content
Publisher Copyright:
Š 2022 The AuthorsElemental content plays an important role in biological processes, and so, the multielemental analysis of human tissue samples is required in biomedical research. Still, the small amount of available biological samples and the adipose content of the samples can be major setbacks for the accurate determination of elemental content. In this study, we explored the potential of several analytical approaches combined with total reflection X-ray fluorescence spectrometry (TXRF) for multielemental analysis of human tissues with different adipose content (colon, heart, liver, lung, muscle, intestine, skin, stomach, uterus, bladder and aorta). The capabilities and limitations of different sample treatment procedures (suspension and acidic digestion) and two TXRF systems with different anode configurations (Mo and W X-ray tubes) have been evaluated for such purpose. Results showed that for tissues with a higher fat content (e.g., skin, and intestine) the best strategy was the acidic digestion of the sample before TXRF analysis. However, for other tissues, acceptable results were obtained by suspending 20 mg of powdered material in 1 mL of 2 M nitric acid. A further enhancement of the limits of detection and accuracy of the results was achieved if using Mo-TXRF systems, especially for the determination of low Z elements (e.g., K, and Ca) and of elements present at low concentrations (e.g., Cu) in the human tissues. Finally, results by TXRF analysis were compared with those obtained with Ο-EDXRF and ICP-OES, and a good agreement was obtained.publishersversionpublishe
Plantes medicinals: medicaments vs. complements alimentosos
Els autors son els estudiants participants de l'assignatura de Plantes Medicinals, EtnobotĂ nica i BioprospecciĂł del grau de FarmĂ cia. Els professors responsables (Joan Simon i Carles BenedĂ) han tutoritzat els treballs i han fet d'editors del treball conjunt. Curs 2020-2021.Sovint es considera al farmacèutic com el professional expert en el medicament, però cada cop mĂŠs a les farmĂ cies trobem complements alimentosos a base de plantes medicinals, comercialitzats en formes farmacèutiques. Fins i tot hi ha laboratoris farmacèutics de renom que tenen lĂnies importants de complements alimentosos. El farmacèutic ha de saber donar consell farmacèutic sobre medicaments, però els complements alimentosos cada cop prenen mĂŠs espai a les farmĂ cies i, sovint, el consell demanat ĂŠs sobre aquests segons.
Amb el nom genèric âPlantes medicinals: medicaments vs. complements alimentososâ, es reuneixen els treballs de curs dels estudiants de lâassignatura de Plantes Medicinals, EtnobotĂ nica i BioprospecciĂł del grau de FarmĂ cia UB, on sâanalitza el doble vessant de les plantes medicinals sota les comercialitzacions de medicaments i/o complements alimentosos. En primer lloc, es determinen de forma comparada els conceptes bĂ sics de medicament, medicament a base de plantes i complement alimentĂłs. DesprĂŠs, en cada cas, fan la descripciĂł botĂ nica corresponent amb indicaciĂł de la part utilitzada, la distribuciĂł geogrĂ fica i els principis actius. A continuaciĂł expliquen les indicacions establertes per lâAgència Europea del Medicament i les diverses formes de comercialitzaciĂł
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