Analysis of perfluorinated compounds in sewage sludge by pressurized solvent extraction followed by liquid chromatography-mass spectrometry

Perfluorinated compounds (PFCs) are widely used in everyday life and one of the main recipients of these compounds is waste water treatment plants (WWTPs). Due to the structure and physicochemical properties of PFCs, these compounds could be redistributed from influent water to sludge. This work reports a new validated protocol for the analysis of 13 perfluorinated acids, 4 perfluorosulfonates and the perfluorooctanesulfonamide. The present work has been focused to develop a sensitive and robust method for the analysis of 18 PFCs in sewage sludge, based on pressurized solvent extraction (PSE) followed by solid phase extraction (SPE) clean-up, analytes separation by liquid chromatography and analysis in a hybrid quadrupole-linear ion trap mass spectrometer (LC-QLiT-MS/MS) working in single reaction monitoring (SRM) mode. The final methodology was validated using a blank sewage sludge fortified at different concentration levels. The method limits of detection were ranging in general from 15 to 79 ng/kg. These values were comparable to the decision limit (CCα) and the detection capability (CCβ), which were 17-1134 ng/kg and 18-1347 ng/kg, respectively. The percentage of recovery was from 79 to 111% in the most cases at different spiked levels. Finally, the repeatability of the method was in the range 4% (PFOS and PFOA) to 25% (RSD %). In order to evaluate the applicability of the method, 5 sludge samples were analyzed. The results showed that the 18 PFCs were present in all samples. However, the concentrations for most of them were below the limits of quantification. The compound present at higher concentrations was perfluorooctanesulfonate (PFOS), which was in concentrations from 53.0 to 121.1 μg/kg. The other PFCs were at concentrations between 0.3 and 30.3 μg/kg.     

Rational design of a Tn antigen mimic

A novel Tn antigen mimic, in which the natural underlying amino acid has been replaced by the non-natural α-methylserine analogue, is reported. This derivative exhibits a similar affinity for a natural lectin as for the natural Tn and retains the bioactive conformation observed in the Tn-containing glycopeptides with anti-MUC1 antibodies.     

Highly selective and sensitive chromo-fluorogenic detection of the Tetryl explosive using functional silica nanoparticles

Silica nanoparticles containing polyamines and thiol groups have been used as probes for the selective detection of Tetryl.     

Radiative efficiencies for fluorinated esters: indirect global warming potentials of hydrofluoroethers

Density Functional Theory (DFT) has been used with an empirically-derived correction for the wavenumbers of vibrational band positions to predict the infrared spectra of several fluorinated esters (FESs). Radiative efficiencies (REs) were then determined using the method of Pinnock et al. and these were used with atmospheric lifetimes from the literature to determine the direct global warming potentials of FESs. FESs, in particular fluoroalkylacetates, alkylfluoroacetates and fluoroalkylformates, are potential greenhouse gases and their likely long atmospheric lifetimes and relatively large REs, compared to their parent HFEs, make them active contributors to global warming. Here, we use the concept of indirect global warming potential (indirect GWP) to assess the contribution to the warming of several commonly used HFEs emitted from the Earth's surface, explicitly taking into account that these HFEs will be converted into the corresponding FESs in the troposphere. The indirect GWP can be calculated using the radiative efficiencies and lifetimes of the HFE and its degradation FES products. We found that the GWPs of those studied HFEs which have the smallest direct GWP can be increased by 100-1600% when taking account of the cumulative effect due to the secondary FESs formed during HFE atmospheric oxidation. This effect may be particularly important for non-segregated HFEs and some segregated HFEs, which may contribute significantly more to global warming than can be concluded from examination of their direct GWPs.     

Faddeev-Jackiw quantization method in conformal three-dimensional supergravity

The conformal supergravity in three space-time dimensions is described by a pure Lorentz-Chern-Simons term. This system has constraints on curvatures and so it is a higher-derivative gauge model. The dynamical properties of this model are analyzed by means of the supersymmetric extension of the Faddeev-Jackiw symplectic quantization method. Using this algorithm in the first-order formalism, we study the gauge supersymmetric transformations and we find the constraints of the model.     

1H, 13C and 15N NMR assignments of phenazopyridine derivatives

Phenazopyridine hydrochloride (1), a drug in clinical use for many decades, and some derivatives were studied by one- and two-dimensional (1)H, (13)C and (15)N NMR methodology. The assignments, combined with DFT calculations, reveal that the preferred protonation site of the drug is the pyridine ring nitrogen atom. The chemoselective acetylation of phenazopyridine (2) and its influence on the polarization of the azo nitrogen atoms were evidenced by the (15)N NMR spectra. Molecular calculations of the phenazopyridines 2-4 show that the pyridine and phenyl groups are oriented in an antiperiplanar conformation with intramolecular hydrogen bonding between the N-b atom and the C-2 amino group preserving the E-azo stereochemistry.     

Membrane association and contact formation by a synthetic analogue of polymyxin B and its fluorescent derivatives

sP-B is a synthetic analogue of the natural lipopeptide antibiotic polymyxin B (PxB) that maintains the ability of the parent compound to form vesicle-vesicle contacts and induce lipid exchange. Exchange is selective, and only monoanionic phospholipids such as 1-palmitoyl-2-oleoyl-glycero-sn-3-phosphoglycerol (POPG) are transferred, whereas dianionic phospholipids such as 1-palmitoyl-2-oleoyl-glycero-sn-3-phosphate (POPA) are not, as shown by fluorescence experiments based on the excimer/monomer ratio of pyrene-labeled phospholipids. Synthetic fluorescent analogues of sP-B are used to investigate the peptide position and orientation in the intermembrane contacts: sP-Bw, an analogue that contains D-tryptophan (D-Trp) instead of the naturally occurring D-phenylalanine, and sP-Bpy, incorporating a pyrene group at the N-terminus. Tryptophan fluorescence, anisotropy, and quenching measurements performed with sP-Bw indicate that the peptide binds and inserts in anionic vesicles of POPG and POPA. However, significant differences are seen depending on the lipid composition, as also demonstrated by fluorescence resonance energy transfer (FRET) experiments from Trp to 7-nitro-2-1,3-benzoxadiazol (NBD) groups at the interface. Intermolecular FRET using sP-Bw as the donor and sP-Bpy as the acceptor indicates self-association of the peptide, possibly forming dimers, when bound to POPG vesicles at concentrations that induce the vesicle-vesicle contacts.     

Current topics on sonoelectrochemistry

Sonoelectrochemistry is undergoing a reemerging activity in the last years with an increasing number of papers appearing in a wide range of peer review journals. Applied studies which cover environmental treatments, synthesis or characterization of nanostructures, polymeric materials synthesis, analytical procedures, films preparations, membrane preparations among other interesting applications have been reviewed. The revised fundamental analyses trying to elucidate the mechanism of the interactions between the ultrasound and electrical fields, are focused on test electrochemical processes, on the use of unconventional solvents and combination with other techniques. After the review of the achievements and faults of sonoelectrochemistry, future research lines are suggested.