Analysis of organic compounds of water-in-crude oil emulsions separated by microwave heating using comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry

In this work the higher peak capacity and resolution of comprehensive two-dimensional gas chromatography (GCxGC) has been successfully applied, for the first time, to tentatively identify several polar organic compounds of organic extracts of aqueous phases resulting from microwave demulsification process of water-in-crude oil emulsions. Results have shown that higher temperatures and longer exposure time to microwave irradiation produced water phases with a wider variety of polar organic compounds. The microwave process showed to be suitable for the extraction of several polar compounds classes of petroleum. The proposed microwave extraction method and GCxGC identification of polar compounds of petroleum samples are of practical interest for the petrochemical industry due to corrosion and related problems associated with these polar compounds in refinery equipments. The GCxGC/time-of-flight MS technique shows to be very important in the total separation of different classes of compounds and allows the identification of many compounds in these classes.     

Use of Fourier transform infrared spectroscopy and chemometrics to discriminate clinical isolates of bacteria of the Burkholderia cepacia complex from different species and ribopatterns

A methodology for the discrimination of Burkholderia cepacia complex (Bcc) clinical isolates at the species level and at the ribopattern level using Fourier transform infrared (FTIR) spectroscopy and chemometrics analysis was assessed in this study. Different Bcc sequential isolates collected at the Santa Maria Hospital (HSM), in Portugal, from clinically infected cystic fibrosis (CF) patients were previously classified by established molecular methods at the species level and differentiated at the strain level, based on their ribopatterns. A set of 185 of these isolates, representing four different Bcc species (Burkholderia cepacia, Burkholderia cenocepacia (recA lineages III-A and III-B), Burkholderia multivorans and Burkholderia stabilis), was analyzed by FTIR and results were processed with chemometric methods. Ten reference strains of these species were used to test the FTIR method. The discrimination at the species level led to misclassification error rates of 10% and 32% for the HSM isolates and reference strains, respectively, clearly indicating that the FTIR classification method was unable to generalize results for the reference strains. Infrared spectra of HSM isolates were further analyzed in terms of the discrimination according to the ribopattern. Results showed misclassification error rates of 4%, 2%, and 8% for B. cepacia, B. cenocepacia III-A, and B. cenocepacia III-B ribopatterns, respectively. These results demonstrated good FTIR spectroscopy discrimination capacity at the ribopattern level, for the HSM isolates but showed difficulty at the species level, especially when the reference strains were included. Remarkably, this methodology was found to discriminate isolates belonging to the same species and ribopattern that were collected from the same patient during prolonged colonization, opening the door to the identification of chemical modifications resulting from adaptation strategies to the CF lung stressing environment, in particular to aggressive and prolonged antibiotic therapy. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Rapid tool for distinction of wines based on the global volatile signature

A new methodology capable of performing the simultaneous analysis of the main surfactants--linear alkylbenzene sulfonates (LAS), alkyl ethoxysulfates (AES), alkyl sulfates (AS), nonylphenol polyethoxylates (NPEOs) and alcohol polyethoxylates (AEOs)--and their carboxylated metabolites--sulfophenyl carboxylic acids (SPCs) and alkylphenol ethoxycarboxylates (APECs)--in environmental samples has been developed for the first time. Extraction is carried out by solid-phase extraction (SPE) and pressurized liquid extraction (PLE) from water and sediment, respectively. Identification and quantification of the target compounds is performed using a liquid chromatography-mass spectrometry (LC-MS) system equipped with an electrospray interface (ESI) operating in mixed-mode. Optimization of parameters such as pH, ionic strength, temperature and solvents has been carried out in order to obtain recoveries in the range from 70 to 107% for most homologs, while the limits of detection are 0.05-0.5 ng mL(-1) in water and 1-10 ng g(-1) in sediment. The proposed methodology has been applied for the simultaneous determination of all the target compounds in samples taken from aquatic ecosystems in the SW of Spain. Values for LAS, AS, AES, NPEOs and AEOs are up to 38.7, 3.0, 2.9, 5.0 and 1.2 microg L(-1) in waters, and in the ranges of 1.73-12.80, 0.11-0.24, 0.02-0.59, 1.94-2.70 and 0.64-3.64 mg kg(-1) in sediments, respectively. The highest concentrations of metabolites found in water are 149.6 microg L(-1) of SPCs and 3.9 microg L(-1) of APECs.     

Vortices as Degenerate Metrics

We note that the Bogomolny equation for abelian vortices is precisely the condition for invariance of the Hermitian–Einstein equation under a degenerate conformal transformation. This leads to a natural interpretation of vortices as degenerate Hermitian metrics that satisfy a certain curvature equation. Using this viewpoint, we rephrase standard results about vortices and make new observations. We note the existence of a conceptually simple, non-linear rule for superposing vortex solutions, and we describe the natural behaviour of the L ²-metric on the moduli space upon restriction to a class of submanifolds.     

Characterization by electrospray ionization and tandem mass spectrometry of rhamnolipids produced by two Pseudomonas aeruginosa strains isolated from Brazilian crude oil

In this work, biosurfactants produced by two Pseudomonas aeruginosa strains isolated from Brazilian crude oils were identified by proton nuclear magnetic resonance ((1)H NMR) and further characterized by mass spectrometry (MS) coupled with electrospray ionization (ESI) and tandem mass spectrometry (MS/MS) analysis in positive mode and their surface activities evaluated. Mono-rhamnolipids and di-rhamnolipids were identified for both isolates, but the most abundant were found to be mono-rhamnolipids. The similarity of rhamnolipids produced by the two strains was in good agreement with their surface activities. Both biosurfactants exhibited similar aqueous solution surface tensions, high emulsification indexes and critical micelle concentration values. The results obtained show that ESI-MS and MS/MS analysis alone provide a fast and highly specific characterization of biosurfactants produced by microbial strains.     

Surface tension of ionic liquids and ionic liquid solutions

Some of the most active scientific research fronts of the past decade are centered on ionic liquids. These fluids present characteristic surface behavior and distinctive trends of their surface tension versus temperature. One way to explore and understand their unique nature is to study their surface properties. This critical review analyses most of the surface tension data reported between 2001 and 2010 (187 references).     

Theoretical study of the absorption and nonradiative deactivation of 1-nitronaphthalene in the low-lying singlet and triplet excited states including methanol and ethanol solvent effects

The photophysics of the 1-nitronaphthalene molecular system, after the absorption transition to the first singlet excited state, is theoretically studied for investigating the ultrafast multiplicity change to the triplet manifold. The consecutive transient absorption spectra experimentally observed in this molecular system are also studied. To identify the electronic states involved in the nonradiative decay, the minimum energy path of the first singlet excited state is obtained using the complete active space self-consistent field∕∕configurational second-order perturbation approach. A near degeneracy region was found between the first singlet and the second triplet excited states with large spin-orbit coupling between them. The intersystem crossing rate was also evaluated. To support the proposed deactivation model the transient absorption spectra observed in the experiments were also considered. For this, computer simulations using sequential quantum mechanic-molecular mechanic methodology was used to consider the solvent effect in the ground and excited states for proper comparison with the experimental results. The absorption transitions from the second triplet excited state in the relaxed geometry permit to describe the transient absorption band experimentally observed around 200 fs after the absorption transition. This indicates that the T(2) electronic state is populated through the intersystem crossing presented here. The two transient absorption bands experimentally observed between 2 and 45 ps after the absorption transition are described here as the T(1)→T(3) and T(1)→T(5) transitions, supporting that the intermediate triplet state (T(2)) decays by internal conversion to T(1).