Ion-exchange Sorbents Research Articles

Development of a new analytical method for the determination of red beetroot betalains using dispersive solid-phase extraction.

The objective of this study was to develop a method for the determination of red beetroot betalains based on the dispersive solid-phase extraction and modified QuEChERS methods followed by micro-high performance liquid chromatography coupled with a mass spectrometer that was equipped with a quadrupole and time-of-flight detector. Currently, new techniques for the extraction of the pigments are necessary and in this study, an extraction of beetroot betalains based on the QuEChERS method was developed for the first time. Twelve variants of the methods with different sorbent combinations were tested. The extraction with 15% methanol and with 0.05% formic acid was performed as a reference method to compare the obtained results. In all of the samples with the addition of sorbents, a lower noise was demonstrated in the obtained results. The betalain concentrations obtained using the tested methods were 0.32-0.54 mg g(-1) , while the value of the reference method was 0.44 mg g(-1) . The method that used the strong ion exchange sorbent (0.44±0.05 mg g(-1) ) was the most adequate in terms of analyzed content, related standard deviation value and interference compared to the reference method. It was concluded that the properly modified QuEChERS method can be successfully applied for the determination of red beetroot betalains.

Description of intraparticle diffusional sorption and desorption processes in ion-exchange sorbents

All general effects of ion exchange kinetics can be considered within the framework of a nonlinear phenomenological diffusional model. According to the model, the dependence of intraparticle diffusivity D on the concentration of sorbed (desorbed) ion a is unknown beforehand and, in general, it should be determined from the experiments by solving the so-called inverse problem. Hence, the work considered some important features of this model relating to the sorption–desorption processes.

A highly selective molecularly imprinted sorbent for extraction of 2-aminothiazoline-4-carboxylic acid – Synthesis, characterization and application in post-mortem whole blood analysis

In this paper, the optimized synthesis and detailed characterization of novel imprinted material for selective extraction of 2-aminothiazoline-4-carboxylic acid (ATCA) were described. The prepolymeric system contained 1-allyl-2-thiourea and ethylene glycol dimethacrylate in methanol, tetrahydrofuran and dimethyl sulfoxide porogenic mixture and 2-aminothiazole-4-carboxylic acid which was used as the template for ATCA. This structural analog of the target analyte was found to provide the imprinted polymer with sufficient binding capacity (60.7±0.9μgg−1) and high selectivity (imprinting factor equal to 18.4) toward ATCA. The adsorption of ATCA was analyzed by the Langmuir model. The heterogeneous population of binding sites on the imprinted polymer was characterized by dissociation constants equal to 3.72μgL−1 and 435μgL−1 for high and low affinity binding sites, respectively. The morphology of the polymer was studied employing SEM and BET analyses and the composition was confirmed by EDS and 13C CP/MAS NMR analyses. Adsorption of amino acids on the imprinted material was tested to analyze the impact of the sample components. The superiority of the imprinted sorbent was proved in a novel dispersive solid phase extraction procedure of ATCA from post-mortem whole blood with respect to the extraction efficacy on the commercial ion-exchange sorbents. The limit of quantification and limit of detection of ATCA in the new analytical method were 12μgL−1 and 3.5μgL−1, respectively. The recovery of ATCA was in the range of 81–89% and the precision of the method ranged from 1.5 to 2.7%.

Radiant Changes of Porous Structure of Ion-Exchange Sorbents Based on Titanium Phosphate and Zirconium Silicate

The effect of bremsstrahlung gamma rays on the surface parameters of microporous amorphous zirconium silicate and on its ability for sorption is studied. The samples were irradiated using a betatron (electron accelerator) with the maximal energy of the g-quanta of 10 MeV and 24 MeV. The surface characteristics of the sorbents were studied by low-temperature adsorption/desorption of nitrogen. The experimental data were processed by BET, DR, and BJH methods. The results show that under exposure to Bremsstrahlung gamma rays the micropores of the sorbent under investigation are partly transformed in mesopores.

Simultaneous analysis of zolpidem and its metabolite in whole blood and oral fluid samples by SPE-LC/MS for clinical and forensic purposes

PurposeThe new analytical method of qualitative and quantitative determination of zolpidem and qualitative analysis of its main metabolite in blood and oral fluid samples was developed. Materials and methodsSample preparation was carried out using a polymeric ion-exchange sorbent in solid phase extraction (SPE). Analysis was realized using liquid chromatography with mass spectrometry detection (LC/MS). The method was validated in terms of few parameters. LOD, LOQ, linearity, precision, selectivity, ion suppression and stability were estimated. ResultsObtained method showed good linearity with determination coefficient (R2) of 0.9989 and 0.9998 for blood and oral fluid samples, respectively. LOD and LOQ of zolpidem were 0.2ng/mL and 1.0ng/mL, respectively, for both blood and oral fluid samples. SPE method recovery varies from 79.9±12.6 to 104.1±1.77 for blood sample and 80.2±0.48 to 103.8±1.51 for oral fluid sample. Samples collected from patients taking zolpidem with a prescription were analyzed. Detection of zolpidem was possible after 15h from ingestion of 10mg zolpidem tartrate in both types of samples. ConclusionThe developed method allows quantitation of zolpidem in therapeutic and subtherapeutic range as well as qualitative analysis of its main metabolite in blood and oral fluid samples. This method meets criteria required for bioanalytical applications and can be used for clinical and forensic purposes.

Cellulose phosphorylation with a mixture of orthophosphoric acid and ammonium polyphosphate in urea medium

Cellulose samples with various extents of structural ordering (native cotton cellulose and mercerized cellulose) were phosphorylated with a mixture of orthophosphoric acid and ammonium polyphosphate in a urea medium. The phosphorus content and ion-exchange capacity of phosphorylated mercerized cellulose are higher than those of the initial natural polysaccharide phosphorylated under the same conditions. Modification of the glucopyranose rings of cellulose mainly occurs in amorphous regions of the polymer. The maximal rate of thermal degradation of cellulose phosphates is considerably lower than that of the initial polymers, and the degradation rate maximum is observed at 238–245°C, in contrast to the main process of dehydration and carbonization of the initial materials, occurring at 330–340°C. The results obtained can be used for preparing ion-exchange sorbents and fireproof fabrics with preset properties.

Folic Acid-fortified Flour: Optimised and Fast Sample Preparation Coupled with a Validated High-Speed Mass Spectrometry Analysis Suitable for a Fortification Monitoring Program

In Australia, folic acid (FA) has been mandatorily added to bread making flour (non-organic wheat flour) since September 2009. The objective of FA fortification is to reduce the prevalence of neural tube defects. This study validated a quantitative assay to determine FA in fortified flour using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). For this purpose, a procedure of aqueous extraction followed by solid phase extraction (SPE) was developed for isolating FA from fortified flour samples. SPE using phenyl cartridges is more selective and avoids the high sodium concentrations used to elute FA from ion exchange sorbents. The validated method is linear over the range 0.024–14 μg/g flour. Absolute recovery of FA was 89 %; inter-day variability coefficient of variation (CV) was 11 % and limit of detection (LOD) was 9.8 ng/g flour. The experimental data revealed that the majority of commercially fortified bread premixes and flour had mean FA concentrations lower than the minimum mandated level of 200 μg/100 g flour. The findings of this study support the need for regular monitoring of actual fortification levels by the Australian States and Territories.

Determination of Endocrine Disrupters and Pharmaceuticals in Sewage Samples by Tandem Solid Phase Clean up/Extraction and High Performance Liquid Chromatography-Negative and Positive Electrospray High-Resolution Mass Spectrometry

A new method for the determination of three endocrine disrupters (estradiol, ethinyl estradiol, and bisphenol A) and five pharmaceuticals (sulfamethoxazole, trimethoprim, diclofenac, bezafibrate and miconazole) in raw sewage samples using tandem solid phase extraction (SPE) sorbents and high-performance liquid chromatography-negative and positive electrospray high-resolution mass spectrometry (HPLC-HRMS) was developed and validated. The SPE procedure used both a strong ion exchange sorbent (SAX) and a modified divinylbenzene-pyrrolidone SPE sorbent to reduce the levels of linear alkylbenzene sulfonate (LAS) and to concentrate the analytes of interest from the sewage samples. The influence of matrix composition on the ionisation efficiency, the SPE recoveries, and the sensitivity of the method was identified and quantified. The method was successfully applied to the determination of analytes in raw sewage samples collected from the entrance of the Arrudas Sewage Treatment Plant, Belo Horizonte, Brazil.

Use of Mixed-Mode Ion Exchange Sorbent for the Passive Sampling of Organic Acids by Polar Organic Chemical Integrative Sampler (POCIS)

Acidic herbicides are increasingly monitored in freshwater, since their high solubility favors their rapid transfer to the water phase. Therefore, contaminant levels in the water can vary rapidly and passive sampling would be preferred over spot sampling to integrate all pollution events over a given exposure time. In this work, we propose to compare the conventional pharmaceutical polar organic chemical integrative sampler (POCIS) with modified POCISs containing two different receiving phases: a standard polystyrene divinylbenzene polymer with a higher specific surface area (Chromabond HR-X) and a mixed-mode anion exchange sorbent providing additional strong anion exchange interaction sites (Oasis MAX). Due to its hydrophobic character, Chromabond HR-X had little interaction with water (no sampling of acidic herbicides); whereas Oasis MAX provided acceptable sampling parameters (longer kinetic regime together with higher sampling rates). Additional experiments with POCIS-MAX showed no influence of nitrates on analyte uptakes, and linear isotherms reaching 10 μg L⁻¹, supporting the applicability of this device for the sampling of organic acids in continental water. The performance and reference compound (PRC) approach would be then applicable for POCIS-MAX if no competition is observed with other anions, especially organic acids (e.g., humic acids).

Stability of phenol-formaldehyde ion-exchange sorbents in aqueous solutions

It is shown that ion-exchange sorbents based on phenol-formaldehyde resins can be used for a long time for isolating and separating rare alkali metals without any significant changes in the ion-exchange selectivity and capacity. When the phenol sorbents were used in alkaline solutions at elevated temperatures, carboxyl groups gradually accumulated in them as a result of the oxidation of methylol groups with oxygen dissolved in the solution. This led to a considerable increase in the ion-exchange capacity of the sorbents and a simultaneous decrease in the selectivity with respect to Cs+-Rb+ and Rb+-K+ ions (it is desirable to avoid the drying of phenol ionites in air by storing them in a swelled state in closed vessels).

Organosilicon derivatives of thiuram disulfide showing sorptive and metallochromic properties

190 Our systematic study in the area of carbofunctional organosilicon monomers and ion exchange and com plexing sorbents derived from them [1, 2] revealed compounds showing metallochromic properties. Such compounds are organosilicon derivatives of dithiocar bamic acid, biguanidine, and iminoguanidine [3], which are not only new organosilicon ionites and complexones but also of interest as test systems of new generation. Test methods developed on the basis of the test systems assume ever greater importance from year to year as express methods demanding no complex instrumentation for detection of elements and their semiquantitative and sometimes quantitative determi nation [4]. The general approach of all chemical test methods consists most frequently in the use of analyt ical reactions and reagents that ensure a visual effect (coloration of different intensity). In continuation of our studies, thiuram disulfide derivatives already used as chromogenic reagents attracted our attention. In particular, tetraethylthi uram disulfide is not only an efficient anti alcohol medicine (Antabuse) but is also used in analytical practice due to formation of colored complexes with a number of elements [5, 6]. For example, it forms with Cu(II) a yellow brown chelate complex known as Mercupral and used as a reagent for determination of silver and mercury [7].

Poly(acrylamide-co-itaconic acid) as a Potential Ion-Exchange Sorbent for Effective Removal of Antibiotic Drug-Ciprofloxacin from Aqueous Solution

This study describes equilibrium and kinetic sorption studies to remove the antibiotic drug Ciprofloxacin (CF) from aqueous solutions using poly(acrylamide-co-itaconic acid) [poly(AAm-co-IA)] as polymeric cation exchanger sorbent material. The co-polymeric sorbent was prepared by free radical induced aqueous polymerization and was characterized by FTIR spectroscopy and TGA analysis. In addition, its physicochemical parameters were also determined. The various isotherm models, when applied to equilibrium sorption data at 28°C, followed the following order: Langmuir > Temkin > Freundlich, with the fair maximum sorption capacity (Q o ) of 178.5 mg g−1. The kinetic sorption data, obtained at 28°C, was applied to kinetic models such as pseudo first order equation, pseudo second order model and a simple Elovich model. Based on regression values, the order of fitness of these models was pseudo second order > pseudo first order > simple Elovich model. The second order adsorption coefficients k2adswere found to be 58 × 10−3, 52.7 × 10−3, 34.01×10−3 g/mg min for drug solutions with initial concentrations of 10, 20 and 30 mg L−1 respectively The sorption mean free energy from the Dubinin–Raduschkevich (DR) isotherm was found to be nearly 8.839 kJ mol−1 indicating an ion-exchange mechanism for drug uptake. The optimum pH value of sorbate solution for drug uptake was found to be around 6.0. Finally, the antibacterial action of drug was investigated and it was found that after adsorption there was a decrease in bacterial growth inhibition efficiency of drug solution.

Overcoming matrix interferences in ion-exchange solid phase extraction of As, Cr, Mo, Sb, Se and V species from leachates of cement-based materials using multiple extractions

Solid phase extraction (SPE) methods based on multiple extractions have been developed to overcome matrix interferences in the charge-based fractionation analysis of As, Cr, Mo, Sb, Se and V leached from cement-based materials. Disposable SPE tubes packed with 500 mg strong anion-exchange (SAX) or strong cation-exchange (SCX) sorbents were used to extract the anionic and cationic species of the elements, respectively. The multiple extractions were based on the percolation of a small sample volume (5.0 mL) through a series of identical ion-exchange tubes. For most of the elements, more than 90% of the anionic species were extracted from a sample containing up to 16 g L −1 NO 3 − by passing the aliquot through five identical SAX tubes. Percolating a sample aliquot through three identical SCX cartridges gave more than 99% retention for Cr(III) from leachates containing a high concentration of interfering metal cations. The anionic and cationic analytes showed only slight non-specific adsorption on the SCX and SAX sorbents, respectively, except for V(V) on the SCX sorbent. A condition was established for the quantitative elution of the retained analytes from the ion-exchange sorbents with 1.0 mol L −1 HNO 3. The multiple ion-exchange SPE procedures were validated using spike recovery tests. The methods were used to determine the anionic and cationic fractions of the target elements in concrete leachates covering a broad range of pH (3.8–13.4). The elements were found to exist predominantly as anions in the alkaline and neutral leachates. A high fraction (85%) of cationic Cr was detected in the most acidic leachate (pH 3.8).

Microfluidic Synthesis of Macroporous Copolymer Particles

Macroporous copolymer particles have a broad range of applications such as ion exchange resins and sorbents, catalyst supports, and carriers of biologically active species. Many of these applications require precise control of the dimensions of microbeads in the range from 50 to 100 µm and predetermined size of pores. This paper reports semicontinuous photoinitiated microfluidic synthesis of macroporous polymer particles with the designated dimensions and a range of internal structures. Comparison with microspheres synthesized by conventional suspension polymerization shows that microfluidic synthesis provides better control over the porous structure of the microbeads.

Sorption of chromium(VI) on ion-exchange resins and sorbents

Sorption of Cr(VI) on AV-17 and EDE-10P anion exchangers, KU-2 and KB-4 cation exchangers, activated charcoal, and foamed graphite (STRG) is studied.

Identification and quantitative determination of priority nonionic and amphoteric surfactants in raw materials and detergent compositions by high-performance liquid chromatography, thin-layer chromatography, and UV spectrometry

A procedure was developed for the group and individual identification of five priority nonionic surfactants and one amphoteric surfactant in raw materials and finished detergents with the use of UV spectrometry, thin-layer chromatography, high-performance liquid chromatography (HPLC) with diode array and refractometric detectors, and solid-phase extraction on an ion-exchange sorbent. A procedure was developed for the determination of these surfactants. The effect of the composition of the organic part of the mobile phase in reversed-phase HPLC on the C18 sorbent with refractometric detection was examined. It was demonstrated that the use of a three-component acetonitrile-methanol-water mobile phase improved the selectivity of the separation of surfactants in comparison with binary acetonitrile-water and methanol-water mixtures.

Bi-Langmuir Isotherms' Applicability for Description of Interaction of Ion-Exchange Sorbents with Protein Mixtures

The sorption of a protein pair on carboxylic cation exchangers with various contents of ionogenic groups is examined. The bi-Langmuir isotherm calculation is carried out from sorption data for single-component systems. It is shown that good agreement of calculated and experimental data is reached only when protein-sorbent interaction weakens because of implementation of the competitive sorption mechanism.

Using on-line solid phase extraction for determination of amiloride in human urine by sequential injection technique

This presented paper deals with a new methodology for the direct determination of amiloride in human urine. The methodology described is based on the sequential injection analysis technique (SIA) coupled with solid phase extraction (SPE) microcolumn. SPE microcolumn was used for selective retention of amiloride, while the urine matrix components were eluted with water carrier flow to the waste. Due to the acid-basic and polarity properties of amiloride molecule and principles of ion-exchange chromatography, it was possible to retain amiloride on the ion-exchange sorbent (SPE BAKER WCX—carboxy group). Eluting solution was 0.01 M HNO 3 + 0.1 M KCl, flow rate 20 μl s −1. The fluorescence detection of amiloride was performed at λ em 385 nm (secondary filter). Recovery was found in the range 96.8–99.4% for 10 times diluted urine, linearity of determination in the range 0.5–100 μg ml −1 ( r = 0.998), and 3 σ limit of detection (LOD) was 0.05 μg ml −1. The whole procedure comprising raw sample pre-treatment, analyte detection and column reconditioning took 8 min. The proposed SIA–SPE method has been applied for direct determination of amiloride in human urine.

Clean (“Green”) Ion-Exchange Technologies. 4. High-Ca-Selectivity Ion-Exchange Material for Self-Sustaining Decalcification of Mineralized Waters Process

This paper (the fourth in a series) reports the results of a theoretical and experimental study of the decalcification of seawater on different ion-exchange sorbents by simultaneous use of electroselectivity reversal and ion-exchange isothermal supersaturation (IXISS) effects. A detailed evaluation of the influence of the sorbent properties on the efficiency of the IXISS-based self-sustaining seawater decalcification process was carried out through a series of computer experiments using a mathematical model of the dynamics of ion exchange. It was found that the best sorbent to be used in the process is a modified A-type zeolite. The modification of the zeolite includes sequential treatment of the initial ion exchanger with dilute magnesium-containing solution (or seawater) and concentrated sodium salt solution. The first treatment was carried out at elevated temperature [15−20 °C higher than the temperature at which the modified zeolite (MZ) is expected to be used, Tex], and the second was performed at Te...

Performance evaluation of two chelating ion-exchange sorbents for the fractionation of labile and inert metal species from aquatic media.

The performance of two iminodiacetate chelating resins, applied in an element fractionation scheme, was investigated for the characterization of marine and stream water samples collected in potentially contaminated harbor and industrial zones. The comparison involved an evaluation of the sorption/desorption behavior of Cd, Cu, Pb and Zn on Chelex-100, a sorbent extensively employed for metal speciation studies, and on Lewatit TP-207, a material with similar chelating characteristics for which no applications for fractionation studies are reported. A characterization of the latter resin in terms of the influence of sample pH on the uptake of metals from aqueous solutions and their subsequent acid elution was carried out. Fractionation studies were performed on natural water samples and model solutions resembling their composition, spiked with micromolar concentrations of the metals. The operationally defined fractionation scheme is based on dynamic adsorption of the resin-labile fractions of metals on microcolumns made of the sorbents. This stage is followed by a batch procedure in which the eluent from the column is contacted with fresh resin to discriminate between the relatively stable species unable to react with the resin during the column interaction time, and the strongly complexed metals that do not interact with the sorbent even for periods of several hours. Results were obtained from coarsely filtered sub-samples and from specimens passed through membrane filters of pore size 0.45 and 0.22 microm. The method was also assessed with model solutions of the metals containing variable concentrations (in the 10(-3)-10(-7) molar range) of complex forming agents such as nitrilotriacetic acid and trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid. An additional batch method, in which a fixed amount of resin was contacted with sample solution for increasing periods of time and the amount of metal remaining in solution measured as a function of the elapsed time, was used to obtain information on the kinetics of dissociation of species formed in the presence of added complexants. The behavior of both resins was similar, demonstrating that the discrimination of species derived from experiments with Chelex-100 may be properly validated by independent fractionation tests carried out with Lewatit TP-207. The behavior of the sorbents is also discussed in terms of the possible influence of particulate or colloidal materials and of kinetic effects related to the presence of complexing agents.