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.     

Toward dynamic combinatorial libraries of cryptands

The first examples of dynamic combinatorial libraries of cryptands, created using the chemistry of imines is presented. Experiments, in which two trialdehydes compete for one triamine in a small library, show the full reversibility of cryptand formation, since the library composition is the same irrespective of the sequence of introducing the building blocks to the mixture.     

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.     

On isometric stability of complemented subspaces of L p

We show that the Rudin-Plotkin isometry extension theorem inL _pimplies that whenX andY are isometric subspaces ofL _pandp is not an even integer, 1≤p<∞, thenX is complemented inL _pif and only ifY is; moreover, the constants of complementation ofX andY are equal. We provide examples demonstrating that this fact fails whenp is an even integer larger than 2.     

Polyscias filicifolia (Araliaceae) Hairy Roots with Antigenotoxic and Anti-Photogenotoxic Activity

Hairy root cultures are considered as a valuable source of bioactive phytoconstituents with expanding applicability for their production. In the present study, hairy root cultures of Polyscias filicifolia (Araliaceae), a traditional Southeast Asian medicinal plant, were established. The transformation with Agrobacterium rhizogenes ATCC 15834 allowed to obtain 15 root lines. The K-1 line, demonstrating the highest growth capabilities, was subjected to further investigations. To enhance the biosynthetic potential of hairy roots, methyl jasmonate elicitation approach was applied (MeJA; at different doses and exposure time), with subsequent transfer of elicited roots to control medium. This strategy resulted in chlorogenic acid production up to 1.59 mg/g dry weight. HPLC-PDA-ESI-MS analysis demonstrated variation in extracts composition and allowed to identify different caffeic and ferulic acid derivatives. Next, cytotoxic, antigenotoxic, and anti-photogenotoxic properties of hairy roots extracts were determined. None of the tested extracts were cytotoxic. In addition, they demonstrated significant antigenotoxic activity with the highest protective potential; up to 52% and 49% of inhibition of induction ratio (IR) induced by the 2-aminoanthracene was revealed for extracts derived from hairy roots elicited for 3 days with 50 µM MeJA and roots elicited for 7 days with 100 µM MeJA and then transferred for 30 days to control medium, respectively. These same extracts exhibited the highest anti-photogenotoxic potential, up to 36% of inhibition of chloropromazine-induced genotoxicity.