Neutral Sorbents Research Articles

Combined extraction of manganese during water purification of technogenic solutions

A method for demanganization of technogenic aqueous solutions is presented. This method involves electrocoagulation purification of aqueous systems from high metal contents and extraction of manganese (II) ions by carbon sorbent adsorption. A coagulation technology based on electrogenerated aluminum hydroxide was used. According to diffraction analysis, such a hydroxide exhibits an amorphous porous hydrogel structure with a developed sorbing surface. The micellar structure of the as-generated aluminum hydroxide, which was attributed to a modification of gibbsite, is represented by the following colloidal particle: {[m Al(OH)3] nAl(OH)2+ (n-x) OH-}x+ xOH-. The associative process of sorption on gibbsite occurs by dispersion interaction, which is governed by the force of electrostatic attraction of instantaneous and induced dipoles of electrically neutral sorbent molecules and the [Mn (OH2)2(OH)2]0 manganese hydroxo-aquo complex. The adsorption limiting value of manganese ions amounted to 4.9 mmol/g at 298 K and pH 5.8, with the adsorption equilibrium constant reaching 1.36 . 104. The electricity consumption corresponded to 12.0 А.h at an optimal electrocoagulation duration of 15 min and a current density of 1.6 мА/сm2. The final purification of aqueous solutions using carbon sorbents was conducted in a slightly alkaline medium at pH 7.5. The manganese sorption value reached 1.68 mmol/g. Therefore, the resource-saving effect of processing of technogenic hydro-mineral solution is manifested in a significant reduction of heavy metal salts and in obtaining of demanded mixed coagulants of aluminum and iron sulfates from water purification wastes. Another positive effect of electrochemical water purification consist in water disinfection and its improved ogranoleptic parameters.

Separation of multiphosphorylated cyclopeptides and their positional isomers by hydrophilic interaction liquid chromatography (HILIC) coupled to electrospray ionization mass spectrometry (ESI-MS)

Peptides are efficient models used in different fields such as toxicology to study the interactions of several contaminants at the molecular scale, requiring the development of bio-analytical strategies. In this context, Hydrophilic interaction liquid chromatography (HILIC) coupled to electrospray ionization mass spectrometry (ESI-MS) was used to separate synthetic multiphosphorylated cyclopeptides and their positional isomers at physiological pH. We assessed (i) the selectivity of eleven HILIC columns, from different manufacturers and packed with diverse polar sorbents, and (ii) the effect of mobile phase composition on the separation selectivity. The best selectivity and baseline resolution were achieved with the columns grafted by neutral sorbents amide and diol. Furthermore, we investigated the HILIC retention mechanism of these peptides by examining the effect of the number of phosphorylated residues in the peptide scaffold on their retention. The peptide behavior followed the classical hydrophilic partitioning mechanism exclusively on amide and diol columns. This trend was not fully respected on bare and hybrid silica due to the attractive/repulsive interactions of the deprotonated surface silanol groups with the Arginine or Glutamate residues in the peptide scaffold according to the peptide sequence. The position of the phosphorylated amino acid in the peptide backbone also showed to have an impact on the retention, making possible the separation of positional isomers of these multiphosphorylated cyclic peptides using HILIC.

Acid retardation method in analysis of strongly acidic solutions by inductively coupled plasma mass-spectrometry

Acid retardation on the sorbents as a technique for reduction of the acidity of the solutions prior to their analysis by inductively coupled plasma mass spectrometry was proposed and investigated. The proposed scheme provides substantial separation of the analytes and nitric acid, which allows direct introduction of the eluates in plasma without dilution. Two sorbents were examined – AV-17 anion-exchange resin and the Stirosorb 584 sorbent. Sorption and desorption of 38 elements on these sorbents were investigated. The efficiencies of the REEs' sorption on the anion-exchange and neutral sorbents were compared. The higher efficiency of the REEs and HNO3 separation was revealed for the neutral Stirosorb 584 sorbent. It was also found that most elements come out quantitatively of the column filled with the AV-17 resin after pumping 2–4mL of the solution. Wherein, the concentration of nitric acid decreased by 20 times. The anomalous behaviour of Ag, Pb, Th and U on the AV-17 resin was found. These analytes were eluted only after pumping 4 column volumes of deionized water. Na, K, Fe, Al and Li in concentrations within (50–1000mgL−1) range did not affect the recovery of REEs. The potential of ARM technique was demonstrate by the analysis of puriss. HNO3 and silverware. ARM enables to avoid dilution of highly acidic solutions prior to their introduction in ICP-MS.

Pesticide Mixture Toxicity in Surface Water Extracts in Snails (Lymnaea stagnalis) by an in Vitro Acetylcholinesterase Inhibition Assay and Metabolomics.

Many chemicals in use end up in the aquatic environment. The toxicity of water samples can be tested with bioassays, but a metabolomic approach has the advantage that multiple end points can be measured simultaneously and the affected metabolic pathways can be revealed. A current challenge in metabolomics is the study of mixture effects. This study aims at investigating the toxicity of an environmental extract and its most abundant chemicals identified by target chemical analysis of >100 organic micropollutants and effect-directed analysis (EDA) using the acetylcholinesterase (AChE) bioassay and metabolomics. Surface water from an agricultural area was sampled with a large volume solid phase extraction (LVSPE) device using three cartridges containing neutral, anionic, and cationic sorbents able to trap several pollutants classes like pharmaceuticals, pesticides, PAHs, PCBs, and perfluorinated surfactants. Targeted chemical analysis and AChE bioassay were performed on the cartridge extracts. The extract of the neutral sorbent cartridge contained most of the targeted chemicals, mainly imidacloprid, thiacloprid, and pirimicarb, and was the most potent AChE inhibitor. Using an EDA approach, other AChE inhibiting candidates were identified in the neutral extract, such as carbendazim and esprocarb. Additionally, a metabolomics experiment on the central nervous system (CNS) of the freshwater snail Lymnaea stagnalis was conducted. The snails were exposed to the extract, the three most abundant chemicals individually, and a mixture of these. The extract disturbed more metabolic pathways than the three most abundant chemicals individually, indicating the contribution of other chemicals. Most pathways perturbed by the extract exposure overlapped with those related to exposure to neonicotinoids, like the polyamine metabolism involved in CNS injuries. Metabolomics for the straightforward comparison between a complex mixture and single compound toxicity is still challenging but, compared to traditional biotesting, is a promising tool due to its increased sensitivity.

Self‐concentration effects in preparative SEC of mineral electrolytes using nanoporous neutral polymeric sorbents

Separation of mineral electrolytes according to size exclusion mechanism using neutral nanoporous polystyrene sorbents and carbonaceous materials has been examined in detail on hand of HCl and CaCl2 solutions, taken separately and in the mixture. Phase distribution coefficients of the above electrolytes have been measured under static conditions at different concentrations. The k-values and their dependence on the concentration were correlated with the elution curves of the components from a chromatographic column. Both the static and dynamic data suggest a strong dependence of the hydration number and effective size of ions on the concentration. Self-concentration of HCl in small pores and that of CaCl2 outside of small pores exhibits itself in both static and chromatographic experiments and results from the relocation of the components largely within the volume of the initial mixture. Additional apparent "retention" of HCl in the porous volume of the sorbent in concentrated electrolyte mixtures was shown to be caused by the competition between all ions of the system for hydration water. Increased separation selectivity and enhanced self-concentration effects for more concentrated mixtures point to preparative and industrial perspectives of size exclusion chromatography (SEC) of complex electrolyte mixtures on nanoporous neutral sorbents.

Hypercrosslinked polymer microspheres with weak anion-exchange character: Preparation of the microspheres and their applications in pH-tuneable, selective extractions of analytes from complex environmental samples

In the present study, we describe the preparation of two high-specific-surface area hypercrosslinked polymer resins (HXLPPs) in the form of monodisperse microspheres with average diameters around 6 μm, modified subsequently with two amine moieties: 1,2-ethylenediamine (EDA) and piperazine. The two resins were evaluated subsequently as weak anion-exchange (WAX) sorbents in solid-phase extraction (SPE), with the aim being to extract a group of acidic compounds from complex environmental samples and thereby free them from basic compounds, including interferences. The new hypercrosslinked sorbents with WAX capacity (HXLPP-WAX) were benchmarked against commercial, macroporous sorbents, namely Oasis-WAX and Strata-X-AW, and to the corresponding neutral sorbents, namely the HXLPP precursor, Oasis-HLB and Strata-X, with promising results. The off-line SPE method developed using the WAX sorbents was applied to Ebre river water samples and led to high recoveries of all the analytes when 500 ml of sample was applied to the cartridges, whereas lower recoveries were obtained with the neutral sorbents. The HXLPP-WAX resin modified with the EDA moiety displayed the most attractive overall performance characteristics; it was tested further with 1000 ml of Ebre river water samples, spiked at lower levels of the analyte mixture, and with effluent waste water from a treatment plant. In both cases, the resin provided good recoveries and net chromatogram, due to the ion-exchange moieties which enable the selective extraction of target compounds.

Role of zwitterionic structures in the solid-phase extraction based method development for clean up of tetracycline and oxytetracycline from honey

Solid-phase extraction (SPE) based sample clean up of tetracycline (TC) and oxytetracycline (OTC) from honey samples was evaluated using a neutral polymeric sorbent (strata-X), a weak cation exchange polymeric sorbent (strata-X-CW) and a combination of neutral and strong cation exchange sorbents (strata-X plus Strata-Screen-C or strata-X-C). Both TC and OTC are recovered in low yields from the strong cation exchange sorbents strata-X-C and Strata-Screen-C under basic (pH >9) or acidic (pH ≥2) elution conditions. The cleanest extracts along with quantitative recoveries were obtained with strata-X-CW under either acidic or basic elution conditions, as demonstrated by analysis of eluates by both LC/UV and LC/MS–MS. On the other hand, the neutral sorbent (strata-X) was less efficient in eliminating the honey matrix constituents, since it could not retain the tetracyclines with the strong organic wash needed to remove other compounds. The differences in the elution behavior of the strong and weak cation exchange sorbents is rationalized on the basis of divergent deprotonation mechanisms of the tetracyclines, which exist in the zwitterionic structures under the SPE conditions.

Pyrocatechol Violet in Spectrophotometric and Novel Optical Methods

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Equilibria for the adsorption of antibiotics onto neutral polymeric sorbents: Experimental and modeling studies

The objective of this work was to study the equilibria for adsorption of three antibiotics (penicillin V, tetracycline, and cephalosporin C) from water onto commercially available neutral polymeric sorbents. The pH was observed to be an important factor in adsorption as our results suggest that the neutral forms of penicillin V and cephalosporin C are preferentially adsorbed onto the neutral sorbents. Also, sorbent surface chemistry was observed to be important for adsorption, as the antibiotics adsorbed more favorably (both in terms of affinities and enthalpies) onto the aromatic sorbent as compared to the aliphatic ester sorbent. In addition to these thermodynamic measurements, molecular modeling studies and Monte Carlo simulations suggest that adsorption onto aromatic sorbents may involve specific interactions between the planar regions of the antibiotic molecules and the phenyl rings of the aromatic sorbent. The interaction energies predicted from Monte Carlo simulations were observed to provide qualitative agreement with experimentally determined adsorption affinities. (c) 1995 John Wiley & Sons, Inc.