Room temperature imidazolium ionic liquid: a solvent for extraction of carbamates prior to liquid chromatographic analysis

A simple and rapid method for preconcentration of carbamate insecticides, including methomyl, propoxur, carbofuran, carbaryl, isoprocarb, methiocarb and promecarb, has been developed. It was based on a liquid-liquid microextraction using a [C₄MIM][PF₆] room temperature ionic liquid as an extraction solvent prior to analysis by high performance liquid chromatography with UV detection. Experimental parameters affecting the extraction performance, such as the volumes of sample, extractant and dissolving solvent, and extraction time, were studied. Under the selected conditions, the enrichment factors in the range between 10 and 25 could be achieved with the limit of detection in the range of 2-40 μg L⁻¹, and with the relative standard deviations of lower than 0.6 and 10.2% for retention time and peak area, respectively. The proposed method offers advantages in reduction of the exposure danger to toxic solvents used in the conventional liquid-liquid extraction, simplicity of the extraction processes, rapidity, and sensitivity enhancement. The method was demonstrated to apply to the analysis of fruit and natural surface water samples.     

Characterization of fatty acid and triacylglycerol composition in animal fats using silver-ion and non-aqueous reversed-phase high-performance liquid chromatography/mass spectrometry and gas chromatography/flame ionization detection

Fatty acid (FA) and triacylglycerol (TG) composition of natural oils and fats intake in the diet has a strong influence on the human health and chronic diseases. In this work, non-aqueous reversed-phase (NARP) and silver-ion high-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry detection and gas chromatography with flame-ionization detection (GC/FID) and mass spectrometry detection are used for the characterization of FA and TG composition in complex samples of animal fats from fallow deer, red deer, sheep, moufflon, wild boar, cock, duck and rabbit. The FA composition of samples is determined based on the GC/FID analysis of FA methyl esters. In total, 81 FAs of different acyl chain length, double bond (DB) number, branched/linear, cis-/trans- and DB positional isomers are identified. TGs in animal fats contain mainly monounsaturated and saturated FAs. High amounts of branched and trans-FAs are observed in the samples of ruminants. In NARP mode, individual TG species are separated including the separation of trans- and branched TGs. Silver-ion mode provides the separation of TG regioisomers, which enables the determination of their ratios. Great differences in the preference of unsaturated and saturated FAs in the sn-2 position on the glycerol skeleton are observed among individual animal fats. Unsaturated FAs are preferentially occupied in the sn-2 position in all animal samples except for wild boar with the strong preference of saturated FAs in the sn-2 position.     

When is a metallopolymer not a metallopolymer? When it is a metallomacrocycle

We report reactions of cobalt(II) acetate with a series of ditopic bis(tpy) ligands (tpy = 2,2':6',2'-terpyridine) containing flexible polyethyleneoxy spacers (tpy-4'-O{(CH(2))(2)O}(n)-4'-tpy, n = 2, 3, 4 or 6 ligands 1-4, respectively) which result in the formation of complicated mixtures of species, presumed to be both open chain and cyclic species. Well resolved paramagnetically shifted (1)H NMR spectra are a powerful tool for the analysis of these solution systems. Upon equilibration, [n + n] metallomacrocycles are isolated as the dominant (thermodynamic) species in some cases, and the single crystal X-ray structures of [Co(2)(3)(2)][PF(6)](4)·6MeCN and [Co(2)(4)(2)][PF(6)](5)·2MeCN (a mixed cobalt(ii)/cobalt(iii) species) are presented. Oxidation of the equilibrated cobalt(II) mixtures to kinetically inert cobalt(III) species provides additional evidence for the formation of metallomacrocycles as the thermodynamic products. Single crystal structural data for [Co(3)(2)(3)][PF(6)](9)·2MeCN·3.5H(2)O, [Co(2)(3)(2)][PF(6)](6)·10MeCN and [Co(2)(4)(2)][PF(6)](6)·6MeCN confirm the assembly of [2 + 2] and [3 + 3] metallomacrocycles. PGSE NMR spectroscopy has been used to determine the hydrodynamic radii of the solution species.     

Environmental control of solution speciation in cobalt(II) 2,2':6',2'-terpyridine complexes: anion and solvent dependence

In methanol or chloroform/methanol solutions, reactions of Cltpy or MeOtpy (Rtpy = 4'-R-2,2':6',2'-terpyridine) with CoX(2)·xH(2)O (X(-) = Cl(-), [OAc](-), [NO(3)](-) or [BF(4)](-)) result in the formation of equilibrium mixtures of [Co(Rtpy)(2)](2+) and [Co(Rtpy)X(2)]. A study of the solution speciation has been carried out using (1)H NMR spectroscopy, aided by the dispersion of signals in the paramagnetically shifted spectra; on going from a low- to high-spin cobalt(II) complex, proton H(6) of the tpy ligand undergoes a significant shift to higher frequency. For R = Cl and X(-) = [OAc](-), increasing the amount of CD(3)OD in the CD(3)OD/CDCl(3) solvent mixture affects both the relative proportions of [Co(Cltpy)(2)](2+) and [Co(Cltpy)(OAc)(2)] and the chemical shifts of the (1)H NMR resonances arising from [Co(Cltpy)(OAc)(2)]. When the solvent is essentially CDCl(3), the favoured species is [Co(Cltpy)(OAc)(2)]. For the 4'-methoxy-2,2':6',2'-terpyridine, the speciation of mono- and bis(terpyridine)cobalt(II) complexes depends upon the anion, solvent and ligand:Co(2+) ion ratio. The (1)H NMR spectrum of [Co(MeOtpy)(2)](2+) is virtually independent of anion and solvent. In contrast, the signals arising from [Co(MeOtpy)X(2)] depend on the anion and solvent. In the case of X(-) = [BF(4)](-), we propose that the mono(tpy) complex formed in solution is [Co(MeOtpy)L(n)](2+) (L = H(2)O or solvent, n = 1-3). The formation of mono(tpy) species has been confirmed by the solid state structures of [Co(Cltpy)(OAc-O)(OAc-O,O')], [Co(MeOtpy)(OAc-O)(OAc-O,O')], [Co(MeOtpy)(NO(3)-O)(2)(OH(2))] and [Co(MeOtpy)Cl(2)]. The single crystal structure of the cobalt(III) complex [Co(Cltpy)Cl(3)]·CHCl(3) is also reported.     

Ce(IV) complexes with donor-functionalized alkoxide ligands: improved precursors for chemical vapor deposition of CeO2

Thin films of ceria (CeO(2)) have many applications, and their synthesis by liquid-injection MOCVD (metal-organic chemical vapor deposition) or ALD (atomic layer deposition) requires volatile precursor compounds. Here we report the synthesis of a series of homoleptic and heteroleptic Ce(IV) complexes with donor-functionalized alkoxide ligands mmp (1-methoxy-2-methylpropan-2-olate), dmap (1-(dimethylamino)propan-2-olate), and dmop (2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)propan-2-olate) and their potential as precursors for MOCVD and ALD of CeO(2). New complexes were synthesized by alcohol exchange reactions with [Ce(OBu(t))(4)]. [Ce(mmp)(4)] and [Ce(dmap)(4)] were both found to be excellent precursors for liquid-injection MOCVD of CeO(2), depositing high purity thin films with very low carbon contamination, and both have a large temperature window for diffusion controlled growth (350-600 °C for [Ce(mmp)(4)]; 300-600 °C for [Ce(dmap)(4)]). [Ce(mmp)(4)] is also an excellent precursor for liquid-injection ALD of CeO(2) using H(2)O as oxygen source and demonstrates self-limiting growth from 150 to 350 °C. [Ce(dmap)(4)] has lower thermal stability than [Ce(mmp)(4)] and does not show self-limiting growth in ALD. Heteroleptic complexes show a tendency to undergo ligand redistribution reactions to form mixtures in solution and are unsuitable as precursors for liquid-injection CVD.     

Feasibility of Raman microspectroscopic identification of biomarkers through gypsum crystals

Pioglitazone is a medicine of thiazolidinedione (TZD) class with hypoglycemic (antihyperglycemic, antidiabetic) action. Pioglitazone binding to human serum albumin (HSA) was investigated at different temperatures (290, 300 and 310 K) by fluorescence spectroscopic method. Molecular docking study was also carried out besides the experiments. Experimental results revealed that pioglitazone have an ability to quench the intrinsic fluorescence of HSA tryptophan through a static quenching procedure. The binding constant was determined using Stern-Volmer modified equation and energy transfer mechanisms of quenching were discussed. Thermodynamic parameters were also calculated according to enthalpy changes dependence on different temperatures. According to the theoretical and experimental results, hydrogen bonding was found to play a major role in the interaction of pioglitazone with HSA.     

pH-dependent spectral properties of para-aminobenzoic acid and its derivatives

The local environment dictates the structural and functional properties of many important chemical and biological systems. The impact of pH on the photophysical properties of a series of para-aminobenzoic acids is examined using a combination of experimental spectroscopy and quantum chemical calculations. Following photoexcitation, PABA derivatives may undergo an intramolecular charge transfer (ICT) resulting in the formation of a zwitterionic species. The thermodynamics of the excited state reaction and temperature-dependence of the radiative emission processes are evaluated through variable temperature fluorescence spectroscopy carried out in a range of aqueous buffers. Quantum chemical calculations are used to analyze structural changes with modifications at the amine position and different protonation states. The ICT is only observed in the tertiary amine, which calculations show has more sp(2) character than the primary or secondary amines. Thermodynamic analysis indicates the ICT reaction is driven by entropy.     

Assessing Similarity of Random sets via Skeletons

Methodology and Computing in Applied Probability - The paper concerns a method for assessing similarity of realisations of random sets based on a construction of their morphological skeletons and a...     

A low-cost light-scattering detector for the flow-injection nephelometric determination of sulfate.

A simple low-cost flow-through light-scattering detector was developed for determining the particle mass concentration in colloidal suspensions. Employing a laser pointer as a light source and a photodiode IC as a light sensor, the detector was shown to have good sensitivity, yet was small and battery operated. The detector was demonstrated to be effective for the flow-injection nephelometric determination of sulfate by precipitation as barium sulfate.     

Ideals of a C *-algebra generated by an operator algebra

In this paper, we consider ideals of a C ^*-algebra C^*(B){C^*(\mathcal{B})} generated by an operator algebra B{\mathcal{B}} . A closed ideal J í C^*(B){J\subseteq C^*(\mathcal{B})} is called a K-boundary ideal if the restriction of the quotient map on B{\mathcal{B}} has a completely bounded inverse with cb-norm equal to K ⁻¹. For K = 1 one gets the notion of boundary ideals introduced by Arveson. We study properties of the K-boundary ideals and characterize them in the case when operator algebra λ-norms itself. Several reformulations of the Kadison similarity problem are given. In particular, the affirmative answer to this problem is equivalent to the statement that every bounded homomorphism from C^*(B){C^*(\mathcal{B})} onto B{\mathcal{B}} which is a projection on B{\mathcal{B}} is completely bounded. Moreover, we prove that Kadison’s similarity problem is decided on one particular C ^*-algebra which is a completion of the *-double of M₂(\mathbbC){M_2(\mathbb{C})} .