Fast and simple method for determination of fatty acid methyl esters (FAME) in biodiesel blends using X-ray spectrometry

The determination of fatty acid methyl esters (FAME) in diesel fuel blends is an important aspect of production and blending process as well as quality control of distribution operations. In this study, energy-dispersive X-ray fluorescence spectrometer (EDXRF) is used for the first time for determination of FAME in biodiesel blends. The principle of the method is based on intensity difference of X-ray radiation scattered from hydrocarbons and from FAME. The experiment shows that coherent and incoherent radiation, commonly applied for evaluation of the average atomic number of the sample with light matrix, cannot be applied for FAME determination. However, the application of scattered continuous radiation gives excellent correlation between FAME concentration and intensity of scattered radiation. The best results are obtained if continuum is collected in the range of energy between 10.5 and 15.0 keV for rhodium X-ray tube, operated at 35 kV. Linear relationship between the FAME concentration and the inverse of scattered continuous radiation is obtained with the correlation coefficients of 0.999. Standard deviation of measurement is ca. 0.46% (v/v) of FAME and detection limit is 1.2% (v/v) for 600 s counting time and 50% dead-time loss using Si-PIN detector. The investigation shows that crucial issue in determination of FAME in biodiesel blends using EDXRF spectrometer is the precision of measurements resulting from the counting statistics. Therefore, much better results (0.20% (v/v) standard deviation and 0.52% (v/v) detection limit) can be expected if higher intensity of primary radiation is applied and X-ray spectrum is collected by silicon drift detector of high input count rate. For concentration of FAME from 10 to 100% (v/v), the differences between reference method (Fourier transform infrared spectrometry) and the proposed method usually do not exceed 1% (v/v) of FAME. The proposed method is fast, simple and enables FAME determination in wide range of concentration up to 100% of FAME without any sample treatment.     

Structural diversification of the coordination mode of divalent metals with 1,3-propanediaminetetraacetate (1,3-pdta): The missing crystal structure of the s-block metal complex [Sr2(1,3-pdta)(H2O)6]·H2O

This paper reports the synthesis and X-ray characteristics of the missing homonuclear s-block metal complex {[Sr₂(1,3-pdta)(H₂O)₆]·H₂O}_n. In the title compound, the hexadentate 1,3-propanediaminetetraacetate (1,3-pdta) ligand joins to two Sr(II) centers via the diamine chain. Moreover, each Sr(II) is bridged through two carboxylate O atoms and a water molecule to two neighboring Sr(II) ions. The coordination sphere around each Sr(II) ion consists of one diamine nitrogen, four carboxylate oxygens and four water molecules. Comparison with the previously reported M(II)-1,3-pdta complexes reveals that increasing of the ion size results in the incorporation of water molecules into its first coordination sphere and consequent increase of the coordination number (C.N.) from six to seven or eight, while keeping the hexadentate coordination mode of the ligand. Further increase of the metal ion size leads to the loss of the chelating properties of the diamine and formation of a bis-tridentate complex. Associated with it is the change in the binding mode of the carboxylate groups. This forms the basis for classification of divalent metal 1,3-pdta complexes into five distinct structural classes. Additionally, in the present study X-ray powder diffraction and IR spectroscopy were used to distinguish the different structural types of M(II)-1,3-pdta complexes, including Ba[Ba(1,3-pdta)]·2H₂O which has been used for their preparation.     

Synthesis and thermal properties of asymmetrical azo-peresters

Abstract  

New asymmetrical azo-perester derivatives of tert-butyl and tert-amyl hydroperoxides were obtained by reacting azo acids with hydroperoxides in the presence of N,N′-carbonyldiimidazole. The obtained azo-peresters possess two labile functional groups: the azo group and the perester group. Data from dynamic differential scanning calorimetry (DSC) experiments indicate that the azo groups decompose at somewhat lower temperatures than the perester groups.     

A new protocol for synthesis of bifunctional alkynyl[vinyl or (E)-alkenyl]substituted organosilicon compounds

A new efficient route for selective synthesis of various, novel alkynyl(vinyl)substituted silicon (6) and alkynyl[(E)-alkenyl]substituted silicon compounds (9) via silylative coupling of alkynes and their products catalyzed by ruthenium(+2) complexes is described. The tandem procedure facilitates the formation of 9 synthesized in a high yield and stereoselectivity by a sequential silylative coupling of terminal alkynes with divinylsubstituted silicon compounds followed by silylative coupling reaction of 6 with styrenes in the presence of ruthenium hydride complexes ([RuHCl(CO)(PR₃)_3−n]; R = Cy (n = 1), i-Pr (n = 1), Ph (n = 0)).     

Energy transfer and surface plasmon resonance in luminescent materials based on Tb(III) and Ag or Au nanoparticles in silica xerogel

Two-component material consisting of terbium(III) ions doping silica xerogel prepared by sol–gel procedure shows enhanced Tb(III) photoluminescence. We postulate that in this material the enhancement is owing to energy transfer from one of the defect states in silica to emitting states ³D₃ and ⁵D₄ of Tb(III).Surface plasmon resonance effect causes two contrary phenomena. Thus, if in the vicinity of the Tb(III) emission centers are present nanoparticles of Ag, observed is additional improvement of the Tb(III) emission. While, presence of Au nanostructures in the silica doped with Tb(III) causes quenching of the luminescence. In general, both the three-component materials exhibit enhancement of the component silica emission band in the resultant 380 nm band and relatively high thermal stability, especially above 600 °C.     

Overview of Allelopathic Potential of Lemna minor L. Obtained from a Shallow Eutrophic Lake

Allelopathy is an interaction that releases allelochemicals (chemicals that act allelopathically) from plants into the environment that can limit or stimulate the development, reproduction, and survival of target organisms and alter the environment. Lemna minor L. contains chemicals that are allelopathic, such as phenolic acids. Chemical compounds contained in L. minor may have a significant impact on the development and the rate of multiplication and lead to stronger competition, which may enhance the allelopathic potential. Allelopathic potential may exist between L. minor and C. glomerata (L) Kütz. because they occupy a similar space in the aquatic ecosystem, have a similar preference for the amount of light, and compete for similar habitat resources. L. minor and C. glomerata can form dense populations on the water surface. Allelopathy can be seen as a wish to dominate one of the plants in the aquatic ecosystem. By creating a place for the development of extensive mats, an interspecific interaction is created and one of the species achieves competitive success. It is most effective as a result of the release of chemicals by macrophytes into the aquatic environment. Therefore, allelopathy plays a significant role in the formation, stabilization, and dynamics of the structure of plant communities.     

Tree-Code Based Improvement of Computational Performance of the X-ray-Matter-Interaction Simulation Tool XMDYN

In this work, we report on incorporating for the first time tree-algorithm based solvers into the molecular dynamics code, XMDYN. XMDYN was developed to describe the interaction of ultrafast X-ray pulses with atomic assemblies. It is also a part of the simulation platform, SIMEX, developed for computational single-particle imaging studies at the SPB/SFX instrument of the European XFEL facility. In order to improve the XMDYN performance, we incorporated the existing tree-algorithm based Coulomb solver, PEPC, into the code, and developed a dedicated tree-algorithm based secondary ionization solver, now also included in the XMDYN code. These extensions enable computationally efficient simulations of X-ray irradiated large atomic assemblies, e.g., large protein systems or viruses that are of strong interest for ultrafast X-ray science. The XMDYN-based preparatory simulations can now guide future single-particle-imaging experiments at the free-electron-laser facility, EuXFEL.     

Effect of Black Cumin Cake Addition on the Chemical Composition,Glycemic Index,Antioxidant Activity,and Cooking Quality of Durum Wheat Pasta

Pasta is a good carrier for plant enrichment substances due to its popularity among consumers. The purpose of the study was to investigate the functional potential and optimize the recipe of pasta made from durum semolina with the addition of black cumin cake at the level of 5, 10, 15, 20, and 25%. The use of black cumin cake resulted in a statistically significant (p ≤ 0.05) increase in the content of protein, fat, ash, and fiber, including both the insoluble and soluble fractions. A reduction in the digestible carbohydrate content, in vitro starch hydrolysis index (HI), was observed. Pasta with a reduced glycemic index (GI) compared to the semolina control was obtained. The content of polyphenols, including flavonoids, in the cake-enriched pasta increased significantly (p ≤ 0.05), which resulted in higher antioxidant activity against DPPH. The increase in the iron content was over 2.5 times higher in the sample with the 25% addition of black cumin cake than in the control sample. The functional addition significantly (p ≤ 0.05) increased the loss of dry matter and influenced the cooking time of pasta.     

Evaluation of Polycyclic Aromatic Hydrocarbons in Smoked Cheeses Made in Poland by HPLC Method

Smoked cheeses are particularly popular among consumers for their flavor and aroma. Of interest, therefore, is the health aspect related to the likelihood of polycyclic aromatic hydrocarbons (PAHs), which are known carcinogens found in smoked products. Thus, the purpose of this study was to evaluate the occurrence of 15 polycyclic aromatic hydrocarbons (PAHs) in smoked and non-smoked cheeses purchased in Poland to monitor their safety. The level of selected PAHs in cheese samples was determined using the HPLC-DAD-FLD method. Most of the cheeses tested met the maximum level of benzo[a]pyrene (2 μg/kg) and the sum of benz[a]anthracene, chrysene, benzo[b]fluoranthene and benzo[a]pyrene (12 μg/kg) established for these products. However, all the cheeses studied in this work had relatively low amounts of the sum of these compounds compared to the information available in the cheese literature, ranging from <LOD to 24.5 μg/kg. This amount does not pose a health risk to consumers. The predominant PAHs found were naphthalene, phenanthrene, fluorene and acenaphthene. Benzo[a]pyrene, the marker compound representing carcinogenic PAHs, was found in 100% and 0% of Polish smoked and non-smoked cheeses, respectively. Although there are currently no regulations for smoked cheeses and maximum concentrations of PAHs in this type of food product, control of PAHs content in cheeses is important due to the mutagenic and carcinogenic potential of these chemicals.