Determination of Veterinary Pharmaceuticals in Production Wastewater by HPTLC-Videodensitometry

An SPE-HPTLC method for simultaneous identification and quantification of seven pharmaceuticals in production wastewater was optimized and validated. The studied compounds were enrofloxacine, oxytetracycline, trimethoprim, sulfamethazine, sulfadiazine, sulfaguanidine and penicillin G/procaine. The method involves solid-phase extraction on hydrophilic-lipophilic balance cartridges with methanol and HPTLC analysis of extracts on CN modified chromatographic plates followed by videodensitometry at 254 and 366 nm. Optimization of chromatographic separation was performed by systematic variation of the mobile phase composition using genetic algorithm approach and the optimum mobile phase composition for TLC separation was 0.05 M H₂C₂O₄:methanol = 0.81:0.19 (v/v). Linearity of the method was demonstrated in the ranges from 1.5 to 15.0 μg L⁻¹ for enrofloxacine, 100–500 μg L⁻¹ for oxytetracycline, 150–600 μg L⁻¹ for trimethoprim, 300–1100 μg L⁻¹ for sulfaguanidine and 100–400 μg L⁻¹ for sulfamethazine, sulfadiazine and penicillin G/procaine with coefficients of determination higher than 0.991. Mean recoveries ranged from 74.6 to 117.1% and 55.1 to 108.0% for wellspring water and production wastewater, respectively. Only sulfaguanidine showed lower results. The described method has been applied to the determination of pharmaceuticals in wastewater samples from pharmaceutical industry.     

Determination of mercury in crude oil by in-situ thermal decomposition using a simple lab built system

A simple system based on thermal decomposition for the one step determination of mercury has been built. This system was applied to the analysis of crude oil and related products. Samples were directly introduced into the system without the use of chemicals and digestion procedures. After 4 min, matrices and mercury compounds were decomposed, and elemental mercury was collected on a gold sand trap, and then detected by atomic fluorescence spectroscopy (AFS). In principle, any sample can be analyzed by this method provided the sample can be introduced into the system quantitatively. The method detection limit was approximately 0.2 ng/g for 0.04 g of crude oil introduced to the system. Various other samples including, biological, environmental, and general merchandise have been analyzed. Results obtained have been compared with established traditional methods including radiochemical neutron activation analysis (RNAA). Good agreement of results between methods was found. Recoveries were close to 100% for certified reference materials. Results were independent of mercury species and sample types.     

A mass spectral study of the acid-catalysed oxygen exchange in laevulinic acid

The sequence, i.e. site selectivity of the acid-catalysed ¹⁶O/¹⁸O exchange in laevulinic acid (1) is studied by mass spectrometry, ion kinetic energy spectroscopy and accurate mass measurements on 1 and its ¹³C(1)-labelled congener. In the fragmentation pathways all ions of interest in the spectrum of 1 originate from the molecular ion, which may exist in six tautomeric or isomeric forms (1a–1d). The mechanism of gas-phase cyclization of 1a is rationalized in terms of three different pathways. Formation of the most prominent fragment ions and the sequence of ¹⁶O/¹⁸O exchange at the carbonyl and carboxy group are discussed. The results indicate the ions of m/z 56, m/z 61 and m/z 98 to be the only three which have incorporated oxygen atoms originating from the carboxy group in 1 and could thus be used in further elucidadon of the rearrangement mechanism of 5-hydroxymethylfuran (2) or 5-hydroxymethylfuran-2-carbaldehyde (3) into laevulinic acid (1).     

Phase behavior in thin films of cylinder-forming ABA block copolymers: mesoscale modeling

The phase behavior of cylinder-forming ABA block copolymers in thin films is modeled in detail using dynamic density functional theory and compared with recent experiments on polystyrene-block-polybutadiene-block-polystyrene triblock copolymers. Deviations from the bulk structure, such as wetting layer, perforated lamella, and lamella, are identified as surface reconstructions. Their stability regions are determined by an interplay between surface fields and confinement effects. Our results give evidence for a general mechanism governing the phase behavior in thin films of modulated phases.     

What determines the inhibition effectiveness of ATA, BTAH, and BTAOH corrosion inhibitors on copper?

Three corrosion inhibitors for copper-3-amino-1,2,4-triazole (ATA), benzotriazole (BTAH), and 1-hydroxybenzotriazole (BTAOH)-were investigated by corrosion experiments and atomistic computer simulations. The trend of corrosion inhibition effectiveness of the three inhibitors on copper in near-neutral chloride solution is determined experimentally as BTAH ? ATA ? BTAOH. A careful analysis of the results of computer simulations based on density functional theory allowed to pinpoint the superior inhibiting action of BTAH and ATA as a result of their ability to form strong N-Cu chemical bonds in deprotonated form. While these bonds are not as strong as the Cl-Cu bonds, the presence of solvent favors the adsorption of inhibitor molecules onto the surface due to stronger solvation of the Cl(-) anions. Moreover, benzotriazole displays the largest affinity among the three inhibitors to form intermolecular aggregates, such as [BTA-Cu](n) polymeric complex. This is another factor contributing to the stability of the protective inhibitor film on the surface, thus making benzotriazole an outstanding corrosion inhibitor for copper. These findings cannot be anticipated on the basis of inhibitors' molecular electronic properties alone, thus emphasizing the importance of a rigorous modeling of the interactions between the components of the corrosion system in corrosion inhibition studies.     

Standardisation of a European measurement method for the determination of mercury in deposition: results of the field trial campaign and determination of a measurement uncertainty and working range

A standard method for the measurement of mercury in deposition is currently being finalised by Working Group 25 of the European Committee for Standardisation’s Technical Committee 264 ‘Air Quality’, in response to the requirements of the European Union’s Fourth Air Quality Daughter Directive. This paper reports the results of a field measurement programme which was undertaken to assess the uncertainty of the proposed standard method, define its working range and determine its compliance with the required data quality objectives of the Fourth Air Quality Daughter Directive.     

Defect evolution in block copolymer thin films via temporal phase transitions

We study the details of the defect dynamics in thin films of a cylinder-forming polystyrene-block-polybutadiene (SB) diblock copolymer melt. The high temporal resolution of in-situ scanning force microscopy (SFM) uncovers elementary dynamic processes of structural rearrangements on time scales not accessible so far. Short-term interfacial undulations and the formation of transient phases (spheres, perforated lamellae, and lamellae) are observed. We demonstrate that the well-known structural defects are annihilated by short-term phase transitions into what may be considered excited states. These temporary phase transitions are reproduced in simulations based on dynamic self-consistent field theory. We discuss the role of the observed structural evolution in the context of the equilibrium phase behavior in SB thin films.     

Solid phase extraction and HPLC determination of veterinary pharmaceuticals in wastewater

This work focuses on the application of SPE-HPLC analysis of important veterinary pharmaceuticals from different classes in highly complex wastewater matrix. The pharmaceutical investigated included three sulfonamides (sulfamethazine, sulfadiazine and sulfaguanidine), a sulfonamide synergist (trimethoprim), a tetracycline (oxytetracycline), a fluoroquinolone (enrofloxacine) and a β-lactame (penicillin G/procaine). The method involves pre-concentration and clean-up by solid phase extraction (SPE) using Oasis HLB extraction catridges. Final analysis of the selected pharmaceutical compounds was carried out by high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD). Recoveries were ranged from 68.3 to 97.9% with relative standard deviation below 8.4%. Only for sulfaguanidine low recovery was obtained. Limits of quantification were in the range 1.5-100 μg/L depending on pharmaceutical. The described method was applied to the determination of pharmaceuticals in wastewater samples from pharmaceutical industry.     

Dynamical dark energy with a constant vacuum energy density

We present a holographic dark-energy model in which the Newton constant GN$G_N$ scales in such a way as to render the vacuum energy density a true constant. Nevertheless, the model acts as a dynamical dark-energy model since the scaling of GN$G_N$ goes at the expense of deviation of concentration of dark-matter particles from its canonical form and/or of promotion of their mass to a time-dependent quantity, thereby making the effective equation of state (EOS) variable and different from −1 at the present epoch. Thus the model has a potential to naturally underpin Dirac's suggestion for explaining the large-number hypothesis, which demands a dynamical GN$G_N$ along with the creation of matter in the universe. We show that with the aid of observational bounds on the variation of the gravitational coupling, the effective-field theory IR cutoff can be strongly restricted, being always closer to the future event horizon than to the Hubble distance. As for the observational side, the effective EOS restricted by observation can be made arbitrary close to −1, and therefore the present model can be considered as a “minimal” dynamical dark-energy scenario. In addition, for nonzero but small curvature (|Ω_k0|?0.003)$(|{\Omega }_{k0}|?0.003)$, the model easily accommodates a transition across the phantom line for redshifts z?0.2$z?0.2$, as mildly favored by the data. A thermodynamic aspect of the scenario is also discussed.