Development of a screening method for the analysis of organic pollutants in water using dual stir bar sorptive extraction-thermal desorption-gas chromatography–mass spectrometry

The development of a method for screening of organic compounds with a wide range of physico-chemical properties in water, based on dual stir bar sorptive extraction coupled with thermal desorption and gas chromatography–mass spectrometry (dual SBSE-TD-GC–MS) is described. The investigated water sample is divided into two aliquots and extracted with stir bar sorptive extraction at two different conditions: using addition of methanol or sodium chloride, respectively. Following extraction, the two stir bars are inserted into the same glass thermal desorption liner and are simultaneously desorbed and analysed by GC–MS. The method optimisation was performed using 45 environmentally harmful substances with different volatilities (boiling point from 193 to 495 °C), polarity (log K_ow from 2.17 to 8.54) and acido-basic properties. The majority of model compounds was selected from the EU list of priority substances in the field of water policy and from the US EPA method 625, respectively. Optimisation was performed for extraction parameters (sample volume, extraction time, stirring rate, addition of modifiers) as well as for the thermal desorption conditions (desorption flow, desorption time, cryofocusing temperature). Performance characteristics (recovery, repeatability, carryover, linearity, limits of detection and quantification) were determined for the optimised method. An example of analysis of a contaminated groundwater sample is presented.     

Assessment of Chemcatcher passive sampler for the monitoring of inorganic mercury and organotin compounds in water

Abstract

Molecularly imprinted polymers (MIPs) for 4-nitrophenol have been successfully prepared by a thermal polymerization method using 4-vinylpyridine (4-VP) and ethylene glycol dimethacrylate (EDMA) as functional monomer and cross-linker, respectively. The obtained materials were evaluated with respect to their selective recognition properties for 4-nitrophenol by HPLC using organic and aqueous eluents. Furthermore, the specific binding sites that have been created during the polymerization process were analyzed via radioligand binding assays. The successful imprinting against 4-nitrophenol provides a new opportunity for advanced separation materials used in environmental analysis.     

Spectrometric and Chromatographic Study of Reactive Oxidants Hypochlorous and Hypobromous Acids and Their Interactions with Taurine

In this study, we focused on the studying of taurine complexes with phenol and sodium hypochlorite, and of taurine with sodium hypobromite by spectrometry, reverse phase chromatography and ion-exchange chromatography. The formed complexes were studied under various conditions such as temperature (10, 20, 30, 40, 50 and 60 °C), and/or time of interaction (0, 5, 10, 15, 20, 25 and 30 min). In addition, we optimized high performance liquid chromatography coupled with UV detector for detection of taurine and its complexes with the acids. Taurine–phenol–hypochlorite complex was effectively separated under isocratic elution, mobile phase water:methanol 30:70 %, v:v, flow rate 1 mL min^?1 and 55 °C. Taurine-bromamine complex was isolated under the following optimized conditions as isocratic elution, mobile phase water:methanol 85:15 % v:v, flow rate 1 mL min^?1 and 55 °C. The limits of detection (3 S/N) were estimated as 1 μM for both types of complexes, i.e. for taurine. Further, we estimated recovery in one sample of urine (male 25 years), commercially achieved energy drink and tea leaves and varied from 79 to 86 %. Further, we aimed our attention at investigating the ability of the above characterized taurine and taurine complexes to scavenge reactive oxygen species. For this purpose, an ion-exchange liquid chromatography with post-column derivatization with ninhydrin and VIS detector was used. It clearly follows from the results obtained that taurine itself reacts with peroxide more intensely than in a bound form, which can be associated with the highest signal decrease. Complexes stabilized structure taurine against peroxide radicals, resulting in slower decreasing of peak heights. The most stable was taurine complexes with phenol and hypobromite.     

Rapid superparamagnetic‐beads‐based automated immunoseparation of Zn‐proteins from Staphylococcus aureus with nanogram yield

Pathogenic bacteria have become a serious socio‐economic concern. Immunomagnetic separation‐based methods create new possibilities for rapidly recognizing many of these pathogens. The aim of this study was to use superparamagnetic particles‐based fully automated instrumentation to isolate pathogen Staphylococcus aureus and its Zn(II) containing proteins (Zn‐proteins). The isolated bacteria were immediately purified and disintegrated prior to immunoextraction of Zn‐proteins by superparamagnetic beads modified with chicken anti‐Zn(II) antibody. S. aureus culture was treated with ZnCl₂. Optimal pathogen isolation and subsequent disintegration assay steps were carried out with minimal handling. (i) Optimization of bacteria capturing: Superparamagnetic microparticles composed of human IgG were used as the binding surface for acquiring live S. aureus. The effect of antibodies concentration, ionic strength, and incubation time was concurrently investigated. (ii) Optimization of zinc proteins isolation: pure and intact bacteria isolated by the optimized method were sonicated. The extracts obtained were subsequently analyzed using superparamagnetic particles modified with chicken antibody against zinc(II) ions. (iii) Moreover, various types of bacterial zinc(II) proteins precipitations from particle–surface interactions were tested and associated protein profiles were identified using SDS‐PAGE. Use of a robotic pipetting system sped up sample preparation to less than 4 h. Cell lysis and Zn‐protein extractions were obtained from a minimum of 100 cells with sufficient yield for SDS‐PAGE (tens ng of proteins). Zn(II) content and cell count in the extracts increased exponentially. Furthermore, Zn(II) and proteins balances were determined in cell lysate, extract, and retentate.     

More on the Problem and the Solution of the Optimal Shape of a Javelin

The analogy between the optimal javelin problem and the problem of determining the optimal shape of the free rotating rod has been established and employed to determine the optimal shape of the javelin via Pontryagin's maximum principle. Five distinct variational principles are constructed for boundary value problem describing optimal shape of the javelin. The first integral for this nonlinear system is found. An a priori estimate of the cross-sectional area is obtained. The optimal shape of the javelin or free rotating rod is determined by numerical integration.     

Interaction of E6 Gene from Human Papilloma Virus 16 (HPV-16) with CdS Quantum Dots

The aim of this study was to analyze the interactions of blue and yellow fluorescent CdS quantum dots (CdS-QDs) with human papillomavirus 16 (HPV-16) oncogene E6. The interactions were investigated using chip capillary electrophoresis, spectrophotometry and square wave voltammetry (SWV). Using chip capillary electrophoresis we proved that blue fluorescent CdS-QDs (0.5 mM) caused an increase of the migration time of the E6 HPV-16 DNA–CdS-QDs complex by 42 s compared to control DNA (E6 HPV-16). The same concentration of yellow fluorescent CdS-QDs caused an increase in the migration time of the DNA–CdS-QDs complex by 108 s compared to the control DNA (E6 HPV-16). The difference in the migration times between both complexes was 66 s. Using square wave voltammetry (SWV), the reduction signal of cytosine and adenine (peak CA) was observed, after the complex with 2.5 µg mL⁻¹ DNA was formed. A decrease of the peak CA reduction signal of the complex DNA–CdS-QDs by 90 % was caused when yellow fluorescent CdS-QDs (0.03 mM) were used. The same concentration of blue fluorescent CdS-QDs caused only a 50 % decrease of the C and A reduction signal of the DNA–CdS-QDs complex. The difference between both CdS-QDs was 40 %. Electrochemical measurements and chip electrophoresis analyses confirmed that the yellow fluorescent CdS-QDs show higher affinity to the DNA (E6 HPV-16) compared to blue ones.

     

Asymmetric allylic substitutions on symmetrical and non-symmetrical substrates using [5]ferrocenophane ligands

A series of [5]ferrocenophane diphosphane ligands were used in Pd-catalyzed allylic substitution reactions. With a symmetrical substrate, 1,3-diphenylpropenyl acetate, enantioselectivities between 70% and 94% ee were observed. Several non-symmetrically substituted allylic substrates were also used. Depending on the substituents of the non-symmetrical allylic substrates, various degrees of regioselectivity (from 1:1 to 100:0) and enantioselectivity (from 0% to 96% ee) were observed. Tentative catalytically active complexes were studied by DFT computational methods.     

Application of Chemcatcher passive sampler for monitoring levels of mercury in contaminated river water

A passive sampler (Chemcatcher) consisting of a 47 mm Empore™ chelating disk (CHE) with iminodiacetic groups as the receiving phase overlaid with a diffusion membrane was developed and calibrated for the monitoring of Hg in water. Three different diffusion membranes including cellulose acetate (CA), polyethersulphone (PS) and cellulose dialysis membrane (D) were tested. The best performance was obtained with the CHE-PS tandem. The effective sampling rate of the device (R_s, L day⁻¹) is defined as the equivalent volume of water extracted per unit time, and is analyte specific and can be determined experimentally in a flow-through tank. Effects of water temperature and turbulence on the uptake rate of Hg were assessed under controlled laboratory conditions. Sampling rates were in the range of 0.029-0.091 L day⁻¹. An increase in sampling rate with turbulence was demonstrated. The detection limit of the sampler obtained in flowing waters ranged between 2.2 and 2.9 ng L⁻¹ Hg. The performance of Chemcatcher was tested alongside spot water sampling in a 14-day field deployment at two locations on the Valdeazogues River, Almadén, Spain. In general, the Hg concentration estimated by the Chemcatcher was lower than that found in spot water samples collected over the same period. This may be explained by the behaviour of this sampler that measures only the labile fraction of Hg in water, and this will exclude some species. However, Chemcatcher preconcentrates Hg allowing its determination in some places where its concentration is below the detection limit of spot sampling.