Basic Eluent Research Articles

Evaluation of a triethylenetetramine-chitosan derivative for the removal of palladium ion from an intricate adsorbate system

Palladium (Pd), a well-known noble metal for its exceptional physical and chemical properties, finds widespread applications in sectors including automotive, hydrogen purification, dentistry, coinage, and jewelry. The growing demand for Pd has led to resource scarcity. This feature necessitated upon the economically and environmentally viable means for the reclamation of the precious metal ions from secondary sources. This article delves into the Pd adsorptive-desorption trends associated with the triethylenetetramine cross-linked chitosan (CH-TETA) derivative in moderately complex solutions. The effect of moderate solution chemistry complexity, incorporating ammonium hydroxide (NH4OH) and ethylenediaminetetraacetic acid (EDTA), within the synthetic electroless plating (ELP) solutions was investigated. Batch adsorption experiments were conducted through a variation of process parameters namely solution pH, CH-TETA dosage, adsorption duration, initial Pd concentration, and temperature. CH-TETA demonstrates an impressive Pd adsorption capacity ranging from 43.53 to 117.08 mg g⁻¹ and is correspondingly accompanied by the metal removal efficiency range of 87.05 % to 39.03 %. Such promising performance has been ascertained for an initial Pd constitution of 50 to 300 mg L⁻¹. Despite constituting other additives in the adsorbate system, utilizing simple acidic and basic eluents, the CH-TETA derivative exhibited a reasonable recovery efficacy of 39.68 %. Thereafter, recovery of Pd can be further enhanced into two approaches. In these, the first refers to the utilization of various other methods such as thermal, electrochemical, ultrasound, and microwave-assisted regeneration from spent adsorbents. Secondly, a pre-treatment method can be adopted to remove the additives prior to the adsorption process. In summary, the recovery of precious metal ions from the spent adsorbents has been a challenging task. Based on the discussion, further improvements based on the findings of this article are possible by targeting relevant research methodologies in resin chemistry and regeneration methods.

Synthesized carboxymethyl-chitosan variant composites for cyclic adsorption-desorption based removal of Fe, Pb, and Cu

The global issue of environmental contamination from industrial wastewater comprising Cu, Fe and Pb demands effective treatment strategies. In this article, a functional composite sorbent was devised to selectively remove copper, iron, and lead from a real-world mimicking wastewater system. For the purpose, high, medium, and low molecular weight chitosan with amine and hydroxyl functional groups were used as a substrate, and glutaraldehyde was used to anchor the organic compound with carboxymethyl groups. Characterization with X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray analyzer accompanied by field emission scanning electron microscope, and Brunauer-Emmett-Teller were conducted for the synthesized adsorbent. Accordingly, the properties of the adsorbent were evaluated to infer that the synthesis assured a purified and functionalized system. The surface area of the medium carboxymethyl chitosan derivative was analyzed as 31.43 m2 g−1. Various adsorption parameters were examined methodically to assess upon optimal removal requirements. The effect of adsorbent dosage, contact time and concentration on the adsorption of the studied metal ions were conducted and the optimum values were achieved at pH 3.82, 540 min contact duration and 1.2 g L−1 sorbent dose. Maximum adsorbent capacities of 344.83 mg g−1, 9.59 mg g−1, and 90.09 mg g−1 were realized for Cu, Pb, and Fe, respectively. The experimental measurements of the studied heavy metal ions inferred the best fitness of Langmuir isotherm equilibrium and pseudo second order kinetic models. Further, elution studies with easy-to-deploy low-cost acidic and basic eluents (HCl, HNO3, H2SO4, KOH, and NaOH) were conducted with cyclic adsorption-desorption strategies. These investigations confirmed the adsorbent's good reusability up to 3 cycles of adsorption and its proximity to serve as a potential material for multi-heavy metal ions elimination from complex adsorbate systems.

Synthesis, Characterization and Investigation of Cross-Linked Chitosan/(MnFe2O4) Nanocomposite Adsorption Potential to Extract U(VI) and Th(IV)

A cross-linked chitosan/(MnFe2O4) CCsMFO nanocomposite was prepared using co-precipitation methods and used as a nanomaterial to extract U(VI) and Th(IV) from an aqueous solution based on adsorption phenomena. The contact time of experiments shows a rapid extraction process within 30 min by the CCsMFO nanocomposite. The solution pH acts a critical role in determining qm value, where pH 3.0 was the best pH value to extract both ions. The pseudo-second-order equilibrium model illustrated the kinetics equilibrium modal extraction process. Adsorption isotherm of U(VI) at pH 3.0 by CCsMFO nanocomposite is an endothermic process. In contrast, the adsorption isotherm of Th(IV) at pH 3.0 by CCsMFO nanocomposite is an exothermic process. The reusability of CCsMFO nanocomposite was tested using basic eluents as suitable conditions for the chemical stability of CCsMFO nanocomposite; the reusability results show promising results for the removal of U(VI) adsorbed onto CCsMFO nanocomposite with 77.27%, after 12 h by Na2CO3 as eluent. At the same time, the reusability results show good reusability for removal of U(VI) adsorbed onto CCsMFO nanocomposite with 21.82%, after 8 h by EDTA as eluent.

Analytical Techniques in Pharmaceutical Analysis for Samples Separation, Characterization, Determination and its Handling

Separations are key aspects of many modern analytical methods. Real world samples contain many analytes. Many analytical methods do not offer sufficient selectivity to be able to speciate all the analytes that might be present. Separation isolates analytes. Most separation methods involve separation of the analytes into distinct chemical species, followed by detection. Instrumental methods may be used to separate samples using chromatography, electrophoresis or field flow fractionation. The development of the pharmaceuticals brought a revolution in human health. These pharmaceutical would serve their intended only if they are free from impurities and administered in appropriate amount. To make drugs serve their purpose various chemical and instrumentation method were developed at regular intervals which are involved in the estimation of drugs. For this analytical instrumentation and methods plays an important role. This review highlights the role of the analytical instrumentation and analytical method in assessing the quality of the drug. The review highlights variety of analytical techniques such as chromatographic, spectroscopic, electrophoretic, titrimetric, microscopic and electrochemical and their corresponding methods that has been applied in the analysis of pharmaceuticals. Quality of pharmaceutical product largely depends upon the environment controls during its storage and handling. Each pharmaceutical product should be handled and stored under specified storage condition labelled on product information data sheet or product pack. Ion chromatography was based on the use of a low-capacity anion exchange separator column used with a basic eluent and a suppressor column. IC is a part of high-performance liquid chromatography used to separate and determine anions and cations. Keywords: Analytical techniques, Sample separation, Chromatography, Spectroscopy, Electrochemical method, Microscopically method, Sample handling, Sample determination Electrophoresis.

Basic eluent for rapid and comprehensive analysis of fatty acid isomers using reversed-phase high performance liquid chromatography/Fourier transform mass spectrometry

Comprehensive separation of fatty acids, including various isomers, is very important for chemical analyses associated with detailed physiological function investigations. We found that a basic eluent is effective for realizing clear separation of double-bond regioisomers by reversed-phase high-performance liquid chromatography. We carried out a comprehensive analysis of fatty acids, including double-bond positional isomers, trans-fatty acids, and iso-fatty acids using reversed-phase high-performance liquid chromatography coupled with Fourier transform mass spectrometry (LC/FTMS). Clear separation of these fatty acids was achieved using a C18 column and a basic eluent. A three-pump gradient system using acetone provided rapid elution within 22 min. In a single run, 184 fatty acid molecular species contained in a dietary fish oil supplement were detected by the FTMS full scan. A previously unreported peak was also detected, which was assigned as tetratriacontadecaenoic acid by comparison with the MS2 profiles of fatty acids with known chemical structures. This result demonstrates that the developed method is useful for clarifying the composition of fatty acid molecular species in target samples, providing a promising approach to discover unreported fatty acids.

Increased electrospray ionization intensities and expanded chromatographic possibilities for emerging contaminants using mobile phases of different pH.

In this work the habitual behaviour of low pH in environmental organic trace analysis is challenged by investigating the full potential of building a multi-component UHPLC-ESI-MS/MS method adapted to cover common emerging contaminants of many different polarities, minimizing the elements of compromise in the performance of the final analytical separation and detection. Contributes have been made by taking advantage of common commercially available technology in understanding the impact from solvent components and the ionization of analytes which can facilitate future development of robust, sensitive and precise UHPLC-MS/MS methods. All contaminants were evaluated and optimized without prejudices regarding historical residence in terms of chromatographic conditions and ESI mode; increasing multi-method's flexibility that can be implemented in routine analysis in response to new requests as well as to emerging contaminants yet to be discovered. Our data strongly supports the questioning of the assumption that equilibrium concentrations of ions in solution reflect those produced during the electrospray process. ESI responses of [M+H](+) and limits of detection were comparable, or often better at high pH compared to acidic eluents. Presence of nitrogen basic groups such as tertiary and secondary amines in a compound increased the intensity of the ESI+ signal, and was even further elevated in basic eluent. The proton affinity probably changes for many nitrogen-containing compounds during the ionization process, making the gas-phase processes very important in generation of these ions by ESI+. There were also an unexpected large number of compounds showing their highest response at pH 7 and weak ionic strength. A flow optimized, buffert free, neutral UHPLC-MS/MS method enhanced the sensitivity for the environmental important synthetic hormone ethinyl estradiol significantly.

Chiral separation of basic compounds on a cellulose 3,5-dimethylphenylcarbamate-coated zirconia monolithin basic eluents by capillary electrochromatography

Porous zirconia monolith (ZM) modified with cellulose 3,5-dimethylphenylcarbamate (CDMPC) was used as chiral stationary phaseto separate basic chiral compounds in capillary electrochromatography. The electroosmotic flow behavior of bare and CDMPC-modified zirconia monolithic (CDMPC-ZM) column was studied in ACN/phosphate buffer eluents of pH ranging from 2 to 12. The CDMPC-ZM column was evaluated by investigatingthe influences of pH, the type and composition of organic modifier of the eluent on enantioseparation. CEC separations at pH 9 provided the best resolutions for the analytes studied, which are better than those observed on CDMPC-modified silica monolithic columns under similar chromatographic conditions. No appreciable decline in retention and resolution factors after over 200 injections, and run-to-run and day-to-day repeatabilities of the column of less than 3% indicate the stability of the zirconia monolithic column in basic media.

Development of Simultaneous Ion-Exclusion/Anion-Exchange Chromatographic Determination of Ammonium, Nitrite and Nitrate Ions and Its Application to High-Salt Content Sample

Simultaneous chromatographic separation of nitrate ion (NO3−), nitrite ion (NO2−) and ammonium ion (NH4+) was obtained using single injection, single column and a detector (conductivity). The principle is based on selective ion-exclusion effect for NH4+ and anion-exchange effects for NO3− and NO2− on an OH−-formed basic anion-exchange resin column (Tosoh TSKgel Super IC-AZ) with basic eluent (2 mol/m3 KOH). The present system could determine NH4+, NO2− and NO3− in 500-fold diluted artificial seawater sample in 40 min at 0.6 mL/min of flow rate, by standard addition method. Also, this method was applicable to nitrogen analysis in artificial seawater with iron matrix, by pre-column packed with an iminodiacetate chelating resin in order to remove iron or calcium ions.

Resins with the ability to bind copper and uranyl ions

AbstractCrosslinked poly(1‐vinyl imidazole‐co‐acrylic acid) and crosslinked poly(1‐vinylmidazole‐co‐2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) were synthesized by radical polymerization and characterized by elemental analysis and FTIR spectroscopy. The polymerization yields were 79 and 99%, respectively. The metal ion binding properties for copper(II) and uranium(VI) were studied under noncompetitive and competitive conditions by Batch equilibrium procedure. The resin crosslinked poly(1‐vinyl imidazole‐co‐acrylic acid) showed a higher dependence on pH than crosslinked poly(1‐vinylmidazole‐co‐2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid). The retention of uranyl ions for the latter resin was close to 100% at pH 5.0. The higher maximum retention capacity was close to 0.8 mmol/g dry resin at pH 5.0. Regeneration of the resin was possible by treatment with basic eluent. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 706–711, 2006

Solid-phase extraction and subsequent capillary zone electrophoresis of trace metal ions as soluble dithiocarbamate complexes

Modest detectability in capillary electrophoresis is often a challenge for the determination of trace-level metal ions. This limitation has been addressed by the development of an enrichment procedure combining the formation of metal bis(carboxymethyl)dithiocarbamate complexes, water soluble at basic pH and sparingly soluble in an acidic environment, and solidphase extraction. Appropriate conditions were developed for a solid-phase extraction step well compatible with subsequent capillary electrophoretic separation in terms of the composition of electrophoresis and eluting buffers. At pH below 4 when the ligand carboxyl groups are non-ionized, metal ion complexes have no apparent charge and are efficiently retained on a conventional C16 cartridge. Application of a basic eluent, a borate buffer at pH9, causes the complexes to be ionized and eluted rapidly and quantitatively. Parameters affecting the retention/recovery behavior, such as the pH and ligand concentration of the loading solution, flow-rate, eluting buffer pH and concentration, etc, were examined to attain the best possible enrichment factors for trace metal ions. As a result, an increase in sensitivity over two orders of magnitude was gained that permitted lowering the detection limits for copper(II), lead(II), cadmium(II), nickel(II), and mercury(II) down to a low-μg L−1 level.

Detection of irradiated food

o-Tyrosine is proposed as a marker for the identification of irradiated protein-rich food. The disadvantages of most of the published methods are insufficient selectivity and the relatively high values of o-tyrosine in unirradiated samples. A method for the analysis of non-protein-bound o-tyrosine in common shrimps is presented here. The procedure involves the homogenization of fresh shrimps followed by solvent precipitation of the proteins with acetone and measurement of the free o-tyrosine by high-performance liquid chromatography with fluorescence detection. The separation is performed using two different separation systems: one based on an acidic eluent and one, used as a reference system, based on a basic eluent. Validation was carried out using a matrix calibration. In unirradiated shrimps a background level of 19.3±7.0 μg/kg (fresh weight) o-tyrosine was found. The content in irradiated shrimps (1 kGy) exceeded the background level by more than 10 times. The radiation dose-response curve was almost linear up to 5 kGy. A survey of the contents of a small market basket was carried out to prove the applicability of the developed method. None of the 11 analysed samples had an o-tyrosine content above the background level.

Anion-exchange separation and determination of bisphosphonates and related analytes by post-column indirect fluorescence detection

Bisphosphonic acids and their salts can be detected after their liquid chromatographic separation by post-column indirect fluorescence detection (IFD). After separation the analyte is combined with the highly fluorescent Al 3+–morin (2′,3,4′,5,7-pentahydroxyflavone) solution and fluorescence decreases because of the formation of the nonfluorescent Al 3+–bisphosphonate complex. The decrease in fluorescence is proportional to the amount of bisphosphonate present. Separation of the multivalent anionic bisphosphonate analytes from other anions and sample matrix is achieved on a strong base anion-exchange column with a strong, basic eluent. The post-column reaction variables, which influence IFD, are identified and optimized for the detection of the bisphosphonates after separation on the anion exchanger. The method is selective, since only a few anions will undergo a reaction with the Al 3+–morin solution, and sensitive, detection limit for difluoromethylene bisphosphonate, F 2MDP, is 4 ng for S/ N=3. The separation–IFD method can be applied to the determination of bisphosphonates, such as F 2MDP, ethane-1-hydroxy-1,1-bisphosphonic acid, dichloromethylene bisphosphonic acid, 4-amino-1-hydroxybutane-1,1-bisphosphonic acid, in biological samples. The separation–IFD method is also applicable to the detection of inositol phosphate anions.

Single-step synthesis of [ 18F]haloperidol from the chloro-precursor and its applications in PET imaging of a cat's brain

We have established a convenient synthesis process for the synthesis of [ 18F]haloperidol using a single-step 18F - for - Cl exchange reaction and a new elution system for the preparative high performance liquid chromatography (HPLC) using C18 bonded vinylalcohol copolymer gel (ODP) and a basic eluent. We successfully applied the product to cat-PET study and got clear images of the striatum, showing the usefulness of this synthesis.

Determination of Organic Phosphates by Column-Switching High Performance Anion-Exchange Chromatography Using On-Line Preconcentration on Titania

A highly selective organic phosphates analyzer was developed based on a column-switching technique using a titania (TiO2) precolumn and an anion-exchange analytical column. In the preliminary examination, it was proved that the titania column strongly retains the organic phosphates under acidic conditions while it shows no retention in alkaline eluents. Based on these findings, the organic phosphates were selectively trapped on the titania precolumn in an acidic eluent, transferred to an anion-exchange column by a basic eluent and detected by coloration after a postcolumn phosphomolybdic acid reaction. When 25.0μM each of phospho-amino acids solution was determined (injection volume, 100μl), the relative standard deviations were 2.3-2.8% (n=5). The detection limits (S/N=3) of the phospho-amino acids were ca. 2.0μM as the injected concentration. The present analyzer was successfully applied to the analysis of the phosphorylation products of a heptapeptide (kemptide).

Chromatographic Hydrophobicity Index by Fast-Gradient RP-HPLC: A High-Throughput Alternative to log P/log D

A new chromatographic hydrophobicity index (CHI) is described which can be used as part of a protocol for high-throughput (50-100 compounds/day) physicochemical property profiling for rational drug design. The index is derived from retention times (t(R)) observed in a fast gradient reversed-phase HPLC method. The isocratic retention factors (log k') were measured for a series of 76 structurally unrelated compounds by using various concentrations of acetonitrile in the mobile phase. By plotting the log k' as a function of the acetonitrile concentration, the slope (S) and the intercept (log k'(w)) values were calculated. The previously validated index of hydrophobicity φ(0) was calculated as -log k'(w)/S. A good linear correlation was obtained between the gradient retention time values, t(R) and the isocratically determined φ(0) values for the 76 compounds. The constants of this linear correlation can be used to calculate CHI. For most compounds, CHI is between 0 and 100 and in this range it approximates to the percentage (by volume) of acetonitrile required to achieve an equal distribution of compound between the mobile and the stationary phases. CHI values can be measured using acidic, neutral, or slightly basic eluents. Values corresponding to the neutral form of molecules could be measured for 52 of the compounds and showed good correlation (r = 0.851) to the calculated octanol/water partition coefficient (c log P) values.

Efficient Medium-Scale Chromatographic Group Separation of Anacardic Acids from Solvent-Extracted Cashew Nut (Anacardium occidentale) Shell Liquid

Biologically active anacardic acids as a group have been separated from the toxic phenolic constituents (cardols and cardanols) of the solvent-extracted cashew nut shell liquid (CNSL) by a novel two-stage chromatographic method. Advantage was taken of the difference in acidity of the two groups of compounds, namely, the carboxylic acids and the phenolics, and the ability of silica gel to selectively retain amines and amine salts. CNSL (1 part) was loaded onto a silica gel bed (5 parts), prepared in a solvent system comprising ethyl acetate-hexane (25 :75) and an organic base (triethylamine, 0.5%). Continued irrigation of the bed with the same eluent resulted in the elution of all the non-acid components. The anacardic acids were subsequently eluted by changing the basic eluent to acidic by replacing the triethylamine with acetic acid (1%). This procedure was shown to be of general applicability for group separation of carboxylic acids.

Macrocyle-based column for the separation of inorganic cations by ion chromatography

A tetradecyl-18-crown-6 (TD18C6) column previously used exclusively for anion separations, has been successfully applied to the separation of mono- and divalent cations. The separation is dependent on the selectivity of the macrocycle for inorganic cations. Because of the unusual selectivity exhibited by TD18C6, this macrocycle-based stationary phase is suitable for the simultaneous separation of three alkaline earth metal cations, five alkali metal cations and the ammonium ion. Due to the similar selectivity of TD18C6 for Mg 2+ and Ca 2+, these ions coelute. The affinity of this column for the hydronium ion is great enough that the cations of interest can be eluted by mildly acidic eluents which are amenable to chemical suppression. The innovations of the macrocycle-based cation chromatographic separation system described herein are fourfold. First, due to the high capacity of the columns, an acidic eluent is employed resulting in a different selectivity than previously seen. The selectivity is unique among macrocycle-based columns because there is no variability in retention times resulting from different counter-anions associated with the analytes. Second, the stationary phase is composed of macrocycle adsorbed onto a non-polar polymer resin, rather than to a silica-based column. This allows for the use of basic eluents for the separation of anions without fear of destroying the polymeric substrate. Third, tetradecyl-substituted 18-crown-6 has not been used in other reported separation schemes of this type. Fourth, this system allows for a greater sensitivity for Cs + because it elutes early in the analysis without coelution. Gradient separations employing organic modifiers, temperature, and pH provided improvements in separation over isocratic analyses.

Application of a pellicular anion-exchange resin to the separation of inorganic and organic anions by single-column anion exchange

Applications are shown of a pellicular anion-exchange resin, prepared by hydrophobically coating a quaternized latex on a mono-disperse, non-porous resin. The low capacity material is ideal for single-column ion chromatography with both conductivity and indirect ultraviolet detection. The pellicular nature of the resin allows rapid isocratic and gradient separations. The resin shows excellent efficiency and is stable under high pressures and over a wide pH range. Stability of the coated resin to pressure, solvents and buffers is discussed. The separation of common inorganic anions, including fluoride, phosphate, chloride, nitrite, bromide, nitrate and sulfate, can be performed at levels below 1 ppm by direct injection. A large number of eluent ions and pH values can be used to optimize the selectivity. Organic acids can be separated rapidly. A rapid separation (11 min) of the common 5'-nucleotide phosphates was performed on the 15-cm column. In addition, a high-efficiency separation of the nucleotides and co-enzymes was performed on a 25-cm column. The elution order of bases was different when performing the separation with acidic and basic eluents.

Electrochemical detection of oligopeptides through the precolumn formation of biuret complexes

The relatively slow kinetics of formation of the electroactive Cu(II)-peptide complexes from larger (>6 amino acids) peptides requires relatively high temperature and long reaction times for a postcolumn reactor. The precolumn incubation of bradykinin, Tyr 8-bradykinin and insulin A chain with biuret reagent for 20 min at 60°C leads to the formation of biuret complexes which can be subjected to chromatography in acidic or basic eluents. These complexes are detected electrochemically with a sensitivity similar to the Cu(II)-(ala) 3, complex (1 nC/pmol at 1.0 ml/min). The influence of the column-packing material on the electrochemical detector response of the Cu-peptide complexes has also been studied.

Gel permeation chromatographic determination of starches using alkaline eluents

By using a dilute solution of sodium hydroxide as eluent in a gel permeation chromatography analysis of natural and modified starches, many of the difficulties encountered with less basic eluent (so-called ghost peaks or memory effects) or with the instability of columns encountered with dimethyl-sulphoxide, are avoided. The system is shown to give reproducible results and no problems with column stability are encounterd after several months' use. Either ordinary refractive index detection or after-column complexation with iodine and spectrophotometric detection are used. The latter system is especially suited for the analysis of changes that occur on amylose during various treatments (entsymatic or acid hydrolysis or extrusion).