Liquid chromatography–high-resolution mass spectrometry for identifying aqueous chlordecone hydrate dechlorinated transformation products formed by reaction with zero-valent iron

Chlordecone (CLD) is a persistent toxic chlorinated pesticide which contaminates different ecosystems in French West Indies. A soil remediation process including zero-valent iron (ZVI) has produced promising results but failed to completely degrade CLD, and the analytical procedures used yielded little information on the transformation products. To fill these gaps, dechlorination of aqueous CLD by micrometric particles of ZVI has been investigated. Aliquots of water with 25% (v/v) of acetone spiked with 100 ppm CLD were taken at different times during a 30-day ZVI treatment and directly analysed by ultra-high-performance liquid chromatography in negative electrospray ionisation mode. CLD has been totally transformed after 14 days into 14 dechlorinated degradation products, including 9 isomeric compounds. The maximum chloride concentrations appearing in the medium represent 44% of that which would result from total dechlorination of CLD. The CLD transformation products identified by accurate mass measurements on an ultra-high-resolution Q-TOF mass spectrometer (Q-TOF-MS) were C₁₀H₃Cl₉O₂, C₁₀H₄Cl₈O₂, C₁₀H₅Cl₇O₂, C₁₀H₆Cl₆O₂ and C₁₀H₇Cl₅O₂. The results show the interest of LC-Q-TOF-MS for identifying transformation products of organic contaminants, and the effectiveness of micrometric ZVI particles to totally transform CLD into less chlorinated products.     

A new method to analyze copolymer based superplasticizer traces in cement leachates

Enhancing the flowing properties of fresh concrete is a crucial step for cement based materials users. This is done by adding polymeric admixtures. Such additives have enabled to improve final mechanicals properties and the development of new materials like high performance or self compacting concrete. Like this, the superplasticizers are used in almost cement based materials, in particular for concrete structures that can have a potential interaction with drinking water. It is then essential to have suitable detection techniques to assess whether these organic compounds are dissolved in water after a leaching process or not. The main constituent of the last generation superplasticizer is a PolyCarboxylate-Ester copolymer (PCE), in addition this organic admixture contains polyethylene oxide (free PEO) which constitutes a synthesis residue. Numerous analytical methods are available to characterize superplasticizer content. Although these techniques work well, they do not bring suitable detection threshold to analyze superplasticizer traces in solution with high mineral content such as leachates of hardened cement based materials formulated with superplasticizers. Moreover those techniques do not enable to distinguish free PEO from PCE in the superplasticizer.Here we discuss two highly sensitive analytical methods based on mass spectrometry suitable to perform a rapid detection of superplasticizer compounds traces in CEM I cement paste leachates: MALDI-TOF mass spectrometry, is used to determine the free PEO content in the leachate. However, industrial copolymers (such as PCE) are characterized by high molecular weight and polymolecular index. These two parameters lead to limitation concerning analysis of copolymers by MALDI-TOFMS. In this study, we demonstrate how pyrolysis and a Thermally assisted Hydrolysis/Methylation coupled with a triple-quadrupole mass spectrometer, provides good results for the detection of PCE copolymer traces in CEM I cement paste leachates.     

Violet-to-blue tunable emission of aryl-substituted dispirofluorene-indenofluorene isomers by conformationally-controllable intramolecular excimer formation

Two series of DiSpiroFluorene-IndenoFluorene (DSF-IF) positional isomers, namely dispiro[2,7-diarylfluorene-9',6,9',12-indeno[1,2-b]fluorenes], (1,2-b)-DSF-IFs 1 and dispiro[2,7-diarylfluorene-9',6,9',12-indeno[2,1-a]fluorenes], (2,1-a)-DSF-IFs 2 have been synthesized. These violet-to-blue fluorescent emitters possess a 3π-2spiro architecture, which combines via two spiro links two different indenofluorene cores, that is, (1,2-b)-IF or (2,1-a)-IF and 2,7-substituted-diaryl-fluorene units. Due to their different geometric profiles, the two families of positional isomers present drastically different properties. The marked difference observed between the properties of (1,2-b)-DSF-IF (1) and (2,1-a)-DSF-IF (2) is discussed in terms of intramolecular π-π interactions occurring in (2,1-a)-DSF-IF (2) leading to conformationally-controllable intramolecular excimer formation. Indeed, the original geometry of the (2,1-a)-DSF-IF (2) family, with face-to-face "aryl-fluorene-aryl" moieties, leads to remarkable excimer emission through intramolecular π-π interactions in the excited state. Furthermore, the emission wavelengths can be gradually modulated by the control of the steric hindrance between the adjacent substituted phenyl rings. Thus, through a comparative and detailed study of the (1)H NMR, electrochemical and photophysical properties of DSF-IFs 1 and 2, we have evidenced the intramolecular π-π interactions occurring between the two "aryl-fluorene-aryl" moieties in the ground state and in the excited state. These properties have been finally correlated to the spectacular conformational change modeled by density functional theory (DFT) calculations. Indeed, the two "aryl-fluorene-aryl" moieties switch from a staggered conformation in the ground state to an eclipsed conformation in the first excited state.     

Noninvasive assessment of hepatic fibrosis in patients with chronic hepatitis C using serum Fourier transform infrared spectroscopy

Assessment of liver fibrosis is of paramount importance to guide the therapeutic strategy in patients with chronic hepatitis C (CHC). In this pilot study, we investigated the potential of serum Fourier transform infrared (FTIR) spectroscopy for differentiating CHC patients with extensive hepatic fibrosis from those without fibrosis. Twenty-three serum samples from CHC patients were selected according to the degree of hepatic fibrosis as evaluated by the FibroTest: 12 from patients with no hepatic fibrosis (F0) and 11 from patients with extensive fibrosis (F3–F4). The FTIR spectra (ten per sample) were acquired in the transmission mode and data homogeneity was tested by cluster analysis to exclude outliers. After selection of the most discriminant wavelengths using an ANOVA-based algorithm, the support vector machine (SVM) method was used as a supervised classification model to classify the spectra into two classes of hepatic fibrosis, F0 and F3–F4. Given the small number of samples, a leave-one-out cross-validation algorithm was used. When SVM was applied to all spectra (n = 230), the sensitivity and specificity of the classifier were 90.1% and 100%, respectively. When SVM was applied to the subset of 219 spectra, i.e., excluding the outliers, the sensitivity and specificity of the classifier were 95.2% and 100%, respectively. This pilot study strongly suggests that the serum from CHC patients exhibits infrared spectral characteristics, allowing patients with extensive fibrosis to be differentiated from those with no hepatic fibrosis.     

A fluctuating quantum model of the CO vibration in carboxyhemoglobin

In this paper, we present a theoretical approach to construct a fluctuating quantum model of the CO vibration in heme-CO proteins and its interaction with external laser fields. The methodology consists of mixed quantum-classical calculations for a restricted number of snapshots, which are then used to construct a parametrized quantum model. As an example, we calculate the infrared absorption spectrum of carboxy-hemoglobin, based on a simplified protein model, and found the absorption linewidth in good agreement with the experimental results.     

Efficient recycling of a chiral palladium catalytic system for asymmetric allylic substitutions in ionic liquid

Chiral carbohydrate-based diphosphites were used for Pd-catalysed asymmetric allylic substitution (alkylation, amination, phosphination) in neat ionic liquids (ILs). Pyrrolidinium-based IL led to the best activities, allowing an efficient catalyst immobilization. In the allylic amination (TOF > 3100 h(-1)), the catalyst could be recycled nine times preserving both activity and enantioselectivity.     

Kinematostatic modeling of compliant parallel mechanisms

The benefits of compliant mechanisms in terms of precision are not easy to exploit because of the limitations of the existing kinematic models used to analyze them. In practice, compliant mechanisms are more sensitive to external wrenches than conventional mechanisms. In this paper, based on the kinematic constraints and the static equilibrium between the joint coordinates and the external wrenches, a general kinematostatic model of compliant parallel mechanisms is presented. Then, this model is differentiated to provide a quasi-static model that makes it possible to calculate the variation of the pose as a linear function of the motion of the actuators and the variation of the external loads through two new matrices: the quasi-static Jacobian matrix and the Cartesian compliance matrix that give a simple and meaningful formulation of the model of the mechanism.