Deep eutectic solvent-based headspace single-drop microextraction for the quantification of terpenes in spices.

Deep eutectic solvents (DESs) were investigated as extracting solvent for headspace single-drop microextraction (HS-SDME). The extraction efficiency of 10 DESs mainly composed of tetrabutylammonium bromide (N4444Br) and long-chain alcohols was evaluated for the extraction of terpenes from six spices (cinnamon, cumin, fennel, clove, thyme, and nutmeg). The DES composed of N4444Br and dodecanol at a molar ratio of 1:2 showed the highest extraction efficiency and was selected to conduct the extractions of terpenes in the rest of the study. HS-SDME was optimized by design of experiments. Only two parameters from the four studied showed a significant influence on the efficiency of the method: the extraction time and the extraction temperature. The optimal extraction conditions were determined by response surface methodology. All extracts were analyzed by gas chromatography coupled to mass spectrometry (GC-MS). More than 40 terpenes were extracted and identified in nutmeg, the richest extract in terpenes in this study. Quantitative analysis based on 29 standards was conducted for each extract. Good linearity was obtained for all standards (R2 > 0.99) in the interval of 1 to 500 µg/g. Limits of quantification ranged from 0.47 µg/g (borneol) to 86.40 µg/g (α-farnesene) with more than half of the values under 2 µg/g. HS-SDME is simple, rapid, and cheap compared with conventional extraction methods. The use of DESs makes this extraction method "greener" and it was shown that DESs can be suitable solvents for the extraction of bioactive compounds from plants.

Dramatic Changes in the Solubilities of Ions Induced by Ligand Addition in Biphasic System D2O/DNO3//[C1C4im][Tf2N]: A Phenomenological Study.

The solubilities of C1C4im(+) and Tf2N(-) in nitric aqueous phases have been measured for several ligand types and concentrations (0.04 M tributylphosphine oxide, 0.05 M N,N'-dimethyl-N,N'-dibutylmalonamide, 0.10 M 1-methyl-3-[4-(dibutylphosphinoyl)butyl]-3H-imidazol-1-ium bis(trifluoromethylsulphonyl)imidate, and 1.1 M N,N-dihexyloctanamide). The data evidence a significant difference between the solubilities of the cations and anions of the ionic liquid as a consequence of several ion-exchange and/or ion-pairing mechanisms involving all ions present in the system as well as the protonation/nitric-extraction ability of the ligand.

Nickel(II) Complexation with Nitrate in Dry [C4mim][Tf2N] Ionic Liquid: A Spectroscopic, Microcalorimetric, and Molecular Dynamics Study.

The complex formation of nitrate ions with nickel(II) in dry [C4mim][Tf2N] ionic liquid (IL) was investigated by means of UV-visible spectrophotometry, isothermal titration calorimetry (ITC), extended X-ray absorption fine structure spectroscopy (EXAFS), and molecular dynamics (MD) simulations. EXAFS spectroscopy and MD simulations show that the solvated Ni(II) cation is initially coordinated by the oxygens of the [Tf2N](-) anion of IL, which can behave either as mono- or bidentate. Spectroscopic and thermodynamic data show that Ni(II) is able to form up to three stable mononuclear complexes with nitrate in this solvent. The stability constants for Ni(NO3)j complexes (j = 1-3) calculated from spectrophotometry and ITC experiments decrease in the order log K1 > log K2 > log K3. The formation of the first two species is enthalpy-driven, while the third species is entropy-stabilized. The UV-vis spectra of solutions containing different nitrate/Ni(II) ratios show that the metal ion retains the six-coordinate geometry. Furthermore, the EXAFS evidences that nitrate is always bidentate. Molecular dynamics simulations show that the [Tf2N](-) anions bind Ni(II) through the sulfonyl oxygen atoms and can coordinate either as monodentate or chelate. The analysis of the MD data shows that introduction of nitrates in the first coordination sphere of the metal ion results in remarkable structural rearrangement of the ionic liquid.

Thallium Transfer from Hydrochloric Acid Media into Pure Ionic Liquids.

Pure hydrophobic ionic liquids are known to extract metallic species from aqueous solutions. In this work we have systematically investigated thallium (Tl) extraction from aqueous hydrochloric acid (HCl) solutions into six pure fluorinated ionic liquids, namely imidazolium- and pyrrolidinium-based ionic liquids with bis(trifluoromethanesulfonyl)imide and bis(fluorosulfonyl)-imide anions. The dependence of the Tl extraction efficiency on the structure and composition of the ionic liquid ions, metal oxidation state, and initial metal and aqueous acid concentrations have been studied. Tl concentrations were on the order of picomolar (analyzed using radioactive tracers) and millimolar (analyzed using inductively coupled plasma mass spectrometry). The extraction of the cationic thallium species Tl(+) is higher for ionic liquids with more hydrophilic cations, while for the TlX(z)(3-z) anionic species (where X = Cl(-) and/or Br(-)), the extraction efficiency is greater for ionic liquids with more hydrophobic cations. The highest distribution value of Tl(III) was approximately 2000. An improved mathematical model based on ion exchange and ion pair formation mechanisms has been developed to describe the coextraction of two different anionic species, and the relative contributions of each mechanism have been determined.

Insights into the mechanism of extraction of uranium (VI) from nitric acid solution into an ionic liquid by using tri-n-butyl phosphate.

We present new results on the liquid-liquid extraction of uranium (VI) from a nitric acid aqueous phase into a tri-n-butyl phosphate/1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (TBP/[C4 mim][Tf2 N]) phase. The individual solubilities of the ionic-liquid ions in the upper part of the biphasic system are measured over the whole acidic range and as a function of the TBP concentration. New insights into the extraction mechanism are obtained through the in situ characterization of the extracted uranyl complexes by coupling UV/Vis and extended X-ray absorption fine structure (EXAFS) spectroscopy. We propose a chemical model to explain uranium (VI) extraction that describes the data through a fit of the uranyl distribution ratio DU . In this model, at low acid concentrations uranium (VI) is extracted as the cationic complex [UO2 (TBP)2 ](2+) , by an exchange with one proton and one C4 mim(+) . At high acid concentrations, the extraction proceeds through a cationic exchange between [UO2 (NO3 )(HNO3 )(TBP)2 ](+) and one C4 mim(+) . As a consequence of this mechanism, the variation of DU as a function of TBP concentration depends on the C4 mim(+) concentration in the aqueous phase. This explains why noninteger values are often derived by analysis of DU versus [TBP] plots to determine the number of TBP molecules involved in the extraction of uranyl in an ionic-liquid phase.

Electric-field alignment of chitin nanorod-siloxane oligomer reactive suspensions.

Uniaxially anisotropic chitin-silica nanocomposite solids have been obtained thanks to the electric field-induced macroscopic alignment of liquid-crystalline reactive cosuspensions. We demonstrate how chitin nanorods (260 nm long, 23 nm thick) can be aligned upon the application of an alternating current (ac) electric field, and within water-ethanol suspensions containing reactive siloxane oligomers (D(h) ∼ 3 nm). The alignment at the millimeter length scale is monitored by in situ small-angle X-ray scattering (SAXS) and polarized light optical microscopy. The composition and state (isotropic, chiral nematic) of the cosuspensions are proven to be determining factors. For nematic phases, the alignment is preserved when the electric field is switched off. Further solvent evaporation induces sol-gel transition, and uniaxially anisotropic chitin-silica nanocomposites are formed after complete drying of the aligned nematic suspensions. Here, the collective response of colloidal mesophases to external electric fields and the subsequent formation of ordered nanocomposite solids would represent a new opportunity for materials design.

Efficient mesoporous silica-titania catalysts from colloidal self-assembly.

Mesoporous silica-titania materials of tunable composition and texture, which present a high catalytic activity in the mild oxidation of sulfur compounds, have been obtained by combining the spray-drying process with the colloidal self-assembly of α-chitin nanorods (biopolymer acting as a template) and organometallic oligomers.