QuEChERS sample preparation followed by ultra-performance liquid chromatography – tandem mass spectrometry for rapid screening of dioctyl sulfosuccinate sodium salt in avian egg tissue

A quantification method was developed for the determination of dioctyl sulfosuccinate sodium salt (DOSS) in avian egg samples based on a QuEChERS extraction technique followed by UPLC-MS/MS analysis. DOSS is an anionic surfactant that is part of the Corexit^® 9500 dispersive mixture that prevents the formation of oil slicks on water bodies. It was extensively used when the Deepwater Horizon rig exploded and a large amount of crude oil was released into the Gulf of Mexico. QuEChERS provided a simple, effective and time saving sample preparation method prior to analysis without reducing analytical sensitivity and became an excellent substitute to lengthy traditional extraction methods. Weak anionic exchange cleanup significantly reduced matrix effects and improved analyte sensitivity. Ultra-performance liquid chromatography provided an effective separation method, while MS/MS provided the necessary selectivity and increased sensitivity. Our method achieved baseline separation of DOSS, surrogate (sodium octyl sulfate – d17) and the internal standard (sodium dioctyl sulfate – d25), with limits of detection (LOD) and limits of quantitation (LOQ) for DOSS being 260 and 500 pg/mL, respectively. Quality control recoveries were 70.5 ± 7.3% (mean ± standard deviation, n = 3) for the laboratory control sample and 72.4 ± 4.9% (n = 3) for the matrix spike. The extraction efficiency was monitored by adding surrogate compound to every sample with recoveries of 104.6 ± 14.1 for SDS-d1 and 81.8 ± 6.8 for SOS-d17. Currently, limited peer reviewed scientific data are reported on the effects of oil dispersants on the environment. Our analytical method for the determination of DOSS in avian egg matrix can be used to provide reliable data on the fate and effects of DOSS in biological systems.     

Highly Functionalized and Potent Antiviral Cyclopentane Derivatives Formed by a Tandem Process Consisting of Organometallic,Transition‐Metal‐Catalyzed,and Radical Reaction Steps

A simple modular tandem approach to multiply substituted cyclopentane derivatives is reported, which succeeds by joining organometallic addition, conjugate addition, radical cyclization, and oxygenation steps. The key steps enabling this tandem process are the thus far rarely used isomerization of allylic alkoxides to enolates and single‐electron transfer to merge the organometallic step with the radical and oxygenation chemistry. This controlled lineup of multiple electronically contrasting reactive intermediates provides versatile access to highly functionalized cyclopentane derivatives from very simple and readily available commodity precursors. The antiviral activity of the synthesized compounds was screened and a number of compounds showed potent activity against hepatitis C and dengue viruses.     

Synthesis,physico-chemical characterization and thermal behavior of new complexes with N4O2 donor set

Three new coordinative compounds of the type [Co(en)₂CO₃]·0.75H₂O (1) and [M(en)₂(H₂O)₂]CO₃ ((2) M:Ni, (3) M:Cu; en: ethylenediamine) were synthesized and characterized. The IR and UV–Vis spectral data indicate that ethylenediamine acts as chelate, while carbonate ions act as bidentate chelate ligand for (1)/counter ion for (2) and (3) generating complexes with octahedral stereochemistry. The thermal behavior provided confirmation of the complexes composition, as well as the number and the nature of water molecules and the intervals of thermal stability. The biological assays revealed a good activity against Enterococcus faecium for copper complex.     

Solubilisation of triolein by microemulsions containing C12E4/hexadecane/water: equilibrium and dynamics

Increasing triolein content of oil-in-water microemulsions in the pure C(12)E(4)/water/n-hexadecane/triolein system while maintaining a fixed surfactant concentration and volume fraction of drops raises the temperature of the solubilisation boundary, where excess oil separates, but has only a slight effect on the (higher) cloud point temperature, where excess water appears. Thus, the temperature range of the single-phase microemulsion shrinks and ultimately disappears. When such microemulsions are in equilibrium with excess oil, the hexadecane/triolein ratio is greater in the microemulsion, probably because the larger triolein molecules are unable to penetrate the hydrocarbon chain region of the surfactant films of the microemulsion droplets. Indeed, monolayer studies and calculations based on microemulsion and excess oil compositions indicate that the films have minimal triolein and similar ratios of hexadecane to surfactant. Triolein drops brought into contact with hexadecane-in-water microemulsions first swell as they incorporate hexadecane, then shrink owing to solubilisation. Interfacial tension decreases during this process until it becomes almost constant near 0.01 mN m(-1), suggesting that the drops in the final stages of solubilisation have high hexadecane contents. A microemulsion containing 10 wt% C(12)E(4) and 15 wt% hexadecane was able to remove over 50% of triolein from polyester fabric at 25 degrees C, more than twice that removed by an oil-free solution with the same surfactant concentration in similar experiments.     

Stereocontrol in radical Mannich equivalents for aminosugar synthesis: haloacetal and 2-(phenylthio)vinyl tethered radical additions to α-hydroxyhydrazones

Studies of stereocontrol in two types of radical equivalents of Mannich addition reactions offer new insights for application to aminosugar synthesis. In the first method, haloacetal addition (Ueno-Stork reaction) is extended to dihydroxyhydrazones, leading to an adduct with the unexpected 3-epi-l-daunosamine configuration. A neighboring α-benzyloxy substituent causes a dramatic reversal of stereocontrol compared with hydrazones where this substituent is absent; vicinal dipole repulsion is proposed to account for the diastereoselectivity. In the second method, radical addition-cyclization with thiophenol and treatment with fluoride leads to diastereoselective group transfer from a silicon-tethered ethynyl group to the CN bond of hydrazones, affording anti-hydrazino alcohols with a trans-2-(phenylthio)vinyl substituent. The one-pot process occurs under neutral, tin-free radical conditions, and offers stereocontrol which is complementary to the haloacetal method. Synthetic utility of the radical Mannich concept is demonstrated in a brief asymmetric synthesis of N-trifluoroacetyl-l-daunosamine from achiral precursors.     

Synthesis, Characterization and Properties of a Novel Cationic Hexanuclear Cyclic Guanidinate Copper(I) Cluster of High Solubility in Non-polar Solvents

The reaction of copper(I) tetra-acetonitrile hexaflourophosphate with LiTEhpp (the lithium salt of 3,3,7,7-tetraethyl-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-??)pyrimidine) at low temperature (?80?°C) in THF under Schlenk conditions, produces a cluster salt tetrakis(3,3,9,9-tetraethyl-1,5,7-triazabicyclo[4.4.0]dec-4ene)bis(hexafluorophosphate)-hexa-copper(I), [Cu₆(TEhpp)₄)](PF₆)₂(1). The cation is composed of an octahedral core of six copper(I) with four TEhpp ligands, each in a tri-coordinating fashion through two N atoms. This compound shows strong luminescent properties at liquid nitrogen temperature and is soluble in non-polar solvents such as toluene and hexane. The synthesis, spectroscopic properties and crystal structure are presented and discussed. The use of CuCl for the reaction with LiTEhpp yields a solution from which, in the presence of water, two mononuclear copper structures are produced in low yield, [Cu(II){(??-O-(HTEhpp)₂}₂Cl][Cu(I)Cl₂], 2, and Cu (TEhpp)₂Cl, 3.     

Acetonitrile Activation Promoted by Divalent Nickel Species with Bicyclic Guanidinate Ligands

Three compounds are described from reactions of divalent nickel species and bicyclic guanidinate ligands. These compounds encompass a variety of nuclearities with one being triangular and having an hour-glass shape and the formula Ni₃(tbn)₆·2LiCl, 1, where tbn is a bicyclic guanidinate anion with fused 5/6 membered rings. A dinuclear compound [(??²-Imeth)Ni(??-tbo)]₂Cl₂, 2, contains two fused 5/5 membered rings (tbo) that bridge two divalent nickel atoms and also contains a chelating unit in each metal center. The neutral Imeth (1-(2,3,5,6-tetrahydro-1H-imidazo[1,2-a]imidazol-1-yl)ethanimine) is an imino-containing ligand produced by the Ni(II) catalyzed reaction of tbo with acetonitrile. A mononuclear species, [(??²-hpp)Ni(hpp)(Hhpp)]Cl, 3, is obtained from reaction of NiCl₂ with the bicyclic guanidinate ligand with two fused six-member rings in contact with moisture. In all compounds each of the Ni atoms has a local square-planar arrangement common in d⁸ species.     

A Monte Carlo approach for estimating measurement uncertainty using standard spreadsheet software

Despite the importance of stating the measurement uncertainty in chemical analysis, concepts are still not widely applied by the broader scientific community. The Guide to the expression of uncertainty in measurement approves the use of both the partial derivative approach and the Monte Carlo approach. There are two limitations to the partial derivative approach. Firstly, it involves the computation of first-order derivatives of each component of the output quantity. This requires some mathematical skills and can be tedious if the mathematical model is complex. Secondly, it is not able to predict the probability distribution of the output quantity accurately if the input quantities are not normally distributed. Knowledge of the probability distribution is essential to determine the coverage interval. The Monte Carlo approach performs random sampling from probability distributions of the input quantities; hence, there is no need to compute first-order derivatives. In addition, it gives the probability density function of the output quantity as the end result, from which the coverage interval can be determined. Here we demonstrate how the Monte Carlo approach can be easily implemented to estimate measurement uncertainty using a standard spreadsheet software program such as Microsoft Excel. It is our aim to provide the analytical community with a tool to estimate measurement uncertainty using software that is already widely available and that is so simple to apply that it can even be used by students with basic computer skills and minimal mathematical knowledge.     

Metastable 11 K Superconductor Na(1-y)Fe(2-x)As(2)

The topochemical deintercalation of Na(+) ions from solid NaFeAs at room temperature in THF with iodine yields the superconducting phase Na(1-y)Fe(2-x)As(2) (T(c) ≈ 11 K). This metastable iron arsenide decomposes at 120 °C and is not accessible by high-temperature solid-state synthesis. X-ray powder diffraction confirms the ThCr(2)Si(2)-type structure, but reveals very small coherently scattering domains with a mean composition Na(0.9(2))Fe(1.7(1))As(2). HRTEM investigations show crystalline as well as strongly distorted areas with planar defects. The latter are probably due to sodium loss and disorder which is also detected by (23)Na solid state NMR. The (57)Fe-M?ssbauer spectrum of Na(1-y)Fe(2-x)As(2) shows one type of iron atoms in tetrahedral coordination. All results point to one crystallographic phase with very small domains due to fluctuations of the chemical composition. From electronic reasons we suggest the superconducting phase is presumably NaFe(2)As(2) in the ordered fractions of the sample.