Initial Analyte Concentration Research Articles

Adsorption of terbium (III) on DGA and LN resins: Thermodynamics, isotherms, and kinetics

Two commercially available extraction chromatography (EXC) resins containing N,N,N’,N’-tetra-n-octyldiglycolamide (DGA Resin, Normal, 50 – 100 μm) and Bis(2-ethylhexyl) phosphate (LN Resin, 100 – 150 μm) were used as adsorbents to study fundamental adsorption properties such as thermodynamic values, equilibrium isotherms, and kinetic uptake models for terbium(III) adsorption. Weight distribution ratios (Dw) for terbium on DGA and LN resins were measured using a [160Tb]Tb3+radiometric tracer in nitric acid as a function of acidity, temperature, initial analyte concentration, and equilibrium time. The Dw values showed increasing binding affinity for DGA resin at high nitric acid concentrations and decreasing binding affinity for LN resins. Thermodynamic studies for DGA and LN resins revealed that the Gibbs free energy (ΔG) increased consistently with temperature. To model equilibrium data, increasingly higher parameter equilibrium isotherm models (Henry (1) < Langmuir, Freundlich (2) < Redlich-Peterson (3) < Fritz-Schluender (4)) were compared on their root mean squared errors (RMSE) and adjusted determination coefficients to determine the most applicable model. In all cases, the empirical four-parameter Fritz-Schluender isotherm demonstrated a superior fit. Similar comparisons for reaction-based kinetic models (Pseudo-first-order < Pseudo-second-order < Pseudo-n-order) revealed that the higher-order PNO model yielded a superior fit of kinetic data for both resins. However, in some cases, adsorption isotherms and kinetic models could also be modeled by a lower-order model with minimal change in error parameters. Weber-Morris plots revealed that two linear sections are observed for each resin, where the first linear segment is attributed to fast (film diffusion) adsorption of terbium, followed by slower intraparticle diffusion of terbium through the pores as the rate-limiting step. Based on the Weber-Morris plot, both film and intraparticle diffusion are involved in controlling the kinetic rate of adsorption for DGA and LN resins.

Sunflower seed pulp ash as an efficient and eco-friendly adsorbent for Congo red uptake: characteristics, kinetics, and optimization

Abstract This investigation focused on the Congo red uptake, as the azo dye, from an aqueous environment. Herein, ash derived from sunflower seed pulp waste (SSPA) was used as an eco-friendly low-cost adsorbent. Based on the BET results, the specific active surface area of SSPA was approximately 102 m2/g. The effect of the initial analyte concentration (10–50 mg/L), the concentration of the adsorbent (1–5 g/L), and the processing time (10–240 min) on the rate of Congo red uptake was also evaluated and optimized. According to the results, the maximum dye removal from synthetic solution (91.89%) was achieved at a dye concentration of 50 mg/L, an adsorbent concentration of 3 g/L, and a processing time of 180 min. The maximum SSPA capacity for Congo red uptake from aquatic solution was 15.34 mg/g, achieving under optimized operational conditions. The adsorption process of SSPA also follows a pseudo-second-order kinetic model (qe = 15.85 mg/g; R2 &amp;gt; 0.99), considering the results of BET and FTIR, suggesting that the rate-controlling step in analyte removal is the chemical interaction between functional groups in SSPA and used dye. Finally, the SSPA washing with different solvents showed that the adsorbent treated with 1 M sodium hydroxide still performed well after his five reuses.

Fabrication of 1-octane sulphonic acid modified nanoporous graphene with tuned hydrophilicity for decontamination of industrial wastewater from organic and inorganic contaminants.

This research work is based on the fabrication of a graphene oxide-based composite (GOBC) to remove the maximum number of contaminants from different industrial effluents. The GO was first intercalated with 1-octanesulphonic acid sodium salt and subjected to microwave irradiation to produce GOBC. Fixed-bed column tests and Jar-tests were performed for removal of the most harmful endocrine disrupting compounds (EDCs) such as bisphenol A, bisphenol S, endosulphan, beta-estradiol, dyes (methylene blue and violate) and toxic metal ions such as Pb2+, Li+, Ni2+, Co2+, Cr6+, Zn2+, Cd2+, Hg2+, Cu2+, and As5+via adsorption. The prepared material was thoroughly characterized for its unique functional and structural properties. The results obtained from Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller, scanning electron microscopy, Raman spectroscopy, water contact angle and X-ray diffraction analysis confirmed the successful preparation of GOBC using the proposed intercalation/microwave method. The water contact angle results showed decreased hydrophilicity of GOBC as compared to GO as the contact angle of GOBC (77.75°) was higher than that of GO (53.98°). The effects of main column parameters such as bed height, initial analyte concentration and solution flow rate were investigated. The results revealed that shorter breakthrough time, and high adsorption capacity were obtained at high flow rates of 1 mL min-1, while longer breakthrough time and lower adsorption capacity were obtained at lower flow rates of 0.5 mL min-1. The effect of bed depth on the breakthrough curve of analyte adsorption was a steep breakthrough curve; or a shorter breakthrough time occurring at lower bed height. The adsorption data obeyed the Yoon-Nelson and Thomas models very well. The adsorption capacity for BPA, BPS, endosulphan, beta-estradiol, methylene blue and violate was found to be 307, 305, 260, 290, 230 and 195 mg g-1, respectively. The adsorption capacity of GOBC for toxic metal ions such as Pb2+, Li+, Ni2+, Co2+, Cr6+, Zn2+, Cd2+, Hg2+, Cu2+, and As5+ was found to be 156, 136, 126, 124, 118, 114, 82, 82, 72 and 72 mg g-1, respectively with excellent kinetics. The adsorption data obtained using Jar-tests revealed that GOBC obeys a Langmuir isotherm and a pseudo second order kinetics model. The analysis of industrial wastewater samples showed good removal efficiency of GOBC.

Adsorption behavior of rhamnolipid modified magnetic Co/Al layered double hydroxide for the removal of cationic and anionic dyes

In the present research, magnetic rhamnolipid-Co/Al layered double hydroxide (MR-LDH) was synthesized to uptake methylene blue (MB) and reactive orange 16 (RO16) from aqueous solution. The main parameters, including pH, adsorbent dosage, contact time, and initial analyte concentration, were optimized to achieve the best adsorption efficiency. Accordingly, the elimination of MB on MR-LDH is improved in the basic medium due to the electrostatic interactions between the negative charge of MR-LDH and the positive charge of MB dye. In contrast, the acidic medium (pH = 3) was favored for RO16 adsorption because of hydrogen bonding between the protonated form of azo dye and protonated hydroxyl groups at the surface of MR-LDH. The calculated maximum adsorption capacities for MB and RO16 were 54.01 and 53.04 mg/g at 313 K, respectively. The Langmuir model, which assumes monolayer adsorption on the adsorbent surface, provides the best explanation for the adsorption of both dyes (R2 = 0.9991 for MB and R2 = 0.9969 for RO16). Moreover, the pseudo-second-order kinetic model best described the adsorption process for MB (R2 = 0.9970) and RO16 (R2 = 0.9941). The proposed adsorbent maintains stable adsorption performance for four consecutive cycles. After each adsorption process, MR-LDH is easily separated by an external magnet. The findings show that MR-LDH was found to be an excellent adsorbent for the removal of both cationic and anionic organic dyes from aqueous solutions.

Biopolymer magnetic chitosan–graphene oxide composite for removal and extraction of aromatic amines from aqueous samples

AbstractBACKGROUNDMagnetic chitosan was crosslinked with graphene oxide and a magnetic chitosan–graphene oxide composite was synthesized and characterized. The composite was used for the removal and extraction of aromatic amines like aniline, N,N‐dimethylaniline and N,N‐diethylaniline.RESULTSExperimental factors affecting the adsorption process such as solution pH, time of contact, amount of adsorbent, initial concentration of analyte and temperature of solution were studied. The maximum adsorption capacity was found to be 7.55 mg g−1 for aniline, 6.96 mg g−1 for N,N‐dimethylaniline and 6.86 mg g−1 for N,N‐diethylaniline using pH 7 at room temperature. Kinetic and adsorption isotherm models were applied to the data which showed the best fit of experimental data to pseudo‐second‐order kinetic model and Langmuir isotherm for all three analytes.CONCLUSIONSThe adsorption process was found to be spontaneous and exothermic as revealed by thermodynamic study. The maximum recoveries for aniline, N,N‐dimethylaniline and N,N‐diethylaniline were 98.56%, 97.05% and 95.26%, respectively. Successful application of the adsorbent was found for spiked aqueous samples. © 2022 Society of Chemical Industry (SCI).

Experimental and computational studies of microwave-assisted watermelon rind – styrene based molecular imprinted polymer for the removal of malachite green from aqueous solution

A microwave-assisted watermelon rind imprinted biosorbent polymer (MAWIMOS) was successfully synthesized and applied as an effective removal of malachite green (MG) dye from wastewater. The successful incorporation of imprinted cavities into the MAWIMOS was confirmed by scanning electron microscopy (SEM), X-ray diffractometry (XRD), and Fourier transform infrared spectroscopy (FTIR). A sequence of adsorption studies was carried out to evaluate the influence of operational parameters such as contact time, initial analyte concentration and temperature on MG removal by the prepared polymer. Equilibrium dye removal was attained within 60 min, giving a % removal of 95.2% at initial MG concentration of 200 mg/L. This value was much higher than 59.3% recorded with non-imprinted polymer (NIP). Thermodynamic studies revealed the spontaneous and exothermic nature of the adsorption process. Kinetic and equilibrium data fitted better to the pseudo-second-order and Freundlich models, respectively. Density functional theory (DFT) study suggested the main interaction mechanism to be by chelation through charge flow from the adsorbent to the MG in solution; and that MG and styrene monomer formed ordered complexes via π−π interactions when the molar ratio between MG and styrene was 1:5. The high quantity of malachite green removed by the MAWIMOS strongly positions the material as an efficient adsorbent for wastewater treatment.

Sulfonated calixarene modified Poly(methyl methacrylate) nanoparticles:A promising adsorbent for Removal of Vanadium Ions from aqueous media

The poly (methyl methacrylate) (PMMA)-based nanoparticle was synthesized by surfactant-free emulsion polymerization method and then post modified with Calixarene using (3-Aminopropyl)triethoxysilane organo-silane as a linker after OH-treatment. The prepared structure was applied for efficient adsorption of Vanadium ions in the aqueous solution after characterization by FT-IR, SEM, TEM, DLS, and EDX. Additional investigations discovered that the prepared adsorbent has a good capacity to adsorb vanadium ions. The effect of key experimental factors was studied to find the optimal point of adsorbent efficiency including the initial concentration of analyte, sorbent dosage, pH of the solution, contact time, and type/quantity of the eluents. It was specified, the maximum adsorption capacity for the synthesized nanoparticles was obtained about 322 mg g−1. The adsorption mechanism was revealed that the model of Langmuir isotherm well-matched compared to the others due to the calculated equilibrium data. Besides, the kinetics of the adsorption process was fitted with pseudo-second-order. Eventually, the prepared adsorbent was successfully applied in vanadium adsorption from real water media.

Preparation, characterization and evaluation of a styrene-based molecularly imprinted polymer for capturing pyridine and pyrrole from crude oil

The rapid increase in global energy demand met with fossil fuel exploration and use as an energy source has not been achieved without its impacts on human and environmental health. Consequently, the imposition of stricter measures on key pollution sources in the effort to reduce the emission of contaminants into the environment became necessary. In this work, a new molecularly imprinted polymer (MIP) targeting pyridine (pyd) and pyrrole (pyr) was synthesized using styrene as a functional monomer. MIP and the non-imprinted polymer (NIP) were characterized by infrared spectroscopy, x-ray spectroscopy, and scanning electron microscopy. The polymer had spongy surfaces and porous network structures. The effects of several factors, such as initial analyte concentration, contact time, and adsorbent dose on pyd and pyr removal efficiencies from crude oil were evaluated. Quantitative analyses indicated that the removal of pyd and pyr occurred at fast kinetics, with a removal efficiency of 15.12 and 15.33, respectively, after 10 min of adsorption time. Optimum adsorption for both analytes was however not reached until 420 min, indicating slow kinetics. The uptake of the analytes increased with a rise in concentration. The highest removal percentages were recorded at 99.9% and 99.7% for pyd and pyr respectively, at 0.06 mol dm−3 adsorbate concentration of the modeling organic media. Two adsorption isotherm models were applied to analyze the equilibrium data, obtaining the best description by the Freundlich isotherm model. The accuracy of the MIP materials was validated using Bonny crude oil from Nigeria. The results showed that the MIP was effective for the adsorption of pyd and pyr in both modeling organic media and real crude oil.

Decontamination of fenitrothion from aqueous solutions using rGO/MoS2/Fe3O4 magnetic nanosorbent: synthesis, characterization and removal application.

In the present work, rGO/MoS2/Fe3O4 nanocomposite was synthesized and after confirmation of the structure by FTIR, XRD, and FESEM techniques, its performance as nanosorbent was investigated for the removal of fenitrothion pesticide from the aqueous media. The parameters affecting the removal process including agitation time, pH of the reaction medium, adsorbent content, initial analyte concentration as well as desorption parameters were investigated and optimized. Under optimum conditions (pH = 7, adsorbent amount: 30mg, adsorption and desorption time: 5min, eluent type and volume: 0.01M ethanol-acetic acid and 4mL), the synthesized adsorbent was able to remove fenitrothion pesticide up to 98% with an adsorption capacity of 33.4mg/g. By investigation of the line equation and the correlation coefficient value, it was found that the adsorption process, in this study, follows the Langmuir model.

A computational simulation of electromembrane extraction based on Poisson - Nernst - Planck equations

Electromembrane extraction (EME) has attracted a great deal of interest in researchers because of its advantages. For analysis, design and optimization purposes, understanding the ion transport mechanisms in the organic supported liquid membrane (SLM) is of prominent importance, where the interplay between the passive diffusion and electric-driven mass transport across SLM affects the mass transfer. In present work, a 2D numerical simulation is developed to examine the mass transfer behavior and the analyte recovery in EME devices. The presented model is capable of describing the effect of different parameters on the recovery of the EME setup. Initial analyte concentration in the sample solution, SLM thickness, applied potential, permittivity, diffusion coefficient, and the reservoir pH within both the sample and acceptor, can be considered as process variables. Predicted results revealed that the most important factors playing key role in EME, are the analyte diffusivity, distribution coefficient of the analyte as well as the level of protonation in both the donor and acceptor solutions. The proposed model is helpful in predicting the mass transfer behavior of the EME process in practical applications.

One-pot synthesis of hematite-alumina hollow sphere composite by ultrasonic spray pyrolysis technique with high adsorption capacity toward PAHs

A hybrid nanocomposite of alumina and hematite was synthesized by ultrasonic spray pyrolysis technique. The study of microscopic images, mapping analysis, and XRD patterns revealed that the Al2O3 – Fe2O3 nanocomposite was composed of separated spherical particles with a thin layer ball-shaped structure that metal oxides are uniformly distributed in the wall of hollow sphere particles, led to a coherent and monotonous construction. A series of coefficients of equilibrium sorption of polycyclic aromatic hydrocarbons (PAHs) as hazardous materials were measured on the prepared composite material in a batch technique. The free or pure Al2O3 or Fe2O3 showed negligible removal efficiency for the mentioned analytes. The various significant variables, such as initial analyte concentration, solution pH, adsorbent dose, and contact time to remove analyte, were studied in the aqueous solutions. Adsorption data were modeled to Langmuir, Freundlich, and Temkin isotherms, and a good correlation found in the case of Langmuir isotherm and adsorption capacity for anthracene, phenanthrene, and naphthalene were 370, 333, and 322 mg g−1, respectively. Investigation of the kinetic models proved a pseudo-second-order, and the prepared adsorbent can be reused more than 7 times without a significant decrease of adsorption performance.

Selective removal of lead ions from aqueous solutions using SiO2–MoO3: Isotherm, kinetics and thermodynamic studies

This study reveals novel data on adsorptive removal of Pb(II) from single metal solution, as well as from multi-metal solution containing Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II) and Zn(II) ions along with Pb(II) using inorganic SiO2–MoO3 sorbent in a batch system. The results of multi-metal solution system were strongly pH-depended and due to occurred precipitation of Fe(III) in the form of hydroxide. The parameters affecting the sorption efficiency (contact time, sorbent dosage and initial analyte concentration) were evaluated for single solution system. The optimal conditions for SiO2–MoO3 sorbent indicated high affinity toward Pb(II) ions within following process parameters; pH value 3, sorbent dosage 50 ​mg and contact time 60 ​min for maximum Pb2+ concentration of 100 ​mg/L. The adsorption data for Pb(II) utilizing SiO2–MoO3 best fit to pseudo-second-order kinetic model (R2 ​= ​0.9998) and Langmuir isotherm model (R2 ​= ​0.9320) with an adsorption capacity of 222.20 ​mg/g and Reff >95%. According to thermodynamic study, the adsorption process is feasible, spontaneous and exothermic (ΔG ​= ​−18.6 ​kJ/mol, ΔH ​= ​−7.5 ​kJ/mol and ΔS ​= ​37.32 ​J/mol K). The results of present study demonstrated that SiO2–MoO3 material as a renewable sorbent for Pb(II) removal.

Organo-Clay as Adsorbent for Removal of Fenoxaprop-p-ethyl from Water Samples; A Statistical Approach

In this study, fuller’s earth (FE) modified with sodium dodecylbenzene sulphonic acid was used for adsorptive removal of fenoxaprop-p-ethyl (FPE) herbicide from water samples and statistical validation of the experimental observations was accomplished. All the adsorption experiments were conducted in batch mode. The effect of pH, agitation time, adsorbent dose and initial herbicide concentration on adsorption process was studied. About 98.5% adsorption efficiency was achieved at initial analyte concentration of 1000 mg L-1 at pH 6 within 60 min at adsorbent dose of 0.1 g. The adsorption kinetics were studied and pseudo-second-order kinetic model was found to follow the adsorption kinetics with R2=0.998. The isotherm studies show that the adsorption data fit well to the Freundlich isotherms. In statistical evaluation, the individual as well as the interaction effect of various factors on adsorption was investigated and it was found that concentration, pH and adsorbent dose are the significant factors with p values of 0.0001, 0.004 and 0.006 respectively, while contact time was found statistically insignificant having p value greater than 0.05. The coefficient of determination (R2=0.930) shows that % adsorption is highly dependent on the studied factors and their interactions. Under the optimized set of conditions, high absorption capacity of 200.22 mg g-1 was achieved.

Organo-Clay as Adsorbent for Removal of Fenoxaprop-p-ethyl from Water Samples; A Statistical Approach

In this study, fuller’s earth (FE) modified with sodium dodecylbenzene sulphonic acid was used for adsorptive removal of fenoxaprop-p-ethyl (FPE) herbicide from water samples and statistical validation of the experimental observations was accomplished. All the adsorption experiments were conducted in batch mode. The effect of pH, agitation time, adsorbent dose and initial herbicide concentration on adsorption process was studied. About 98.5% adsorption efficiency was achieved at initial analyte concentration of 1000 mg L-1 at pH 6 within 60 min at adsorbent dose of 0.1 g. The adsorption kinetics were studied and pseudo-second-order kinetic model was found to follow the adsorption kinetics with R2=0.998. The isotherm studies show that the adsorption data fit well to the Freundlich isotherms. In statistical evaluation, the individual as well as the interaction effect of various factors on adsorption was investigated and it was found that concentration, pH and adsorbent dose are the significant factors with p values of 0.0001, 0.004 and 0.006 respectively, while contact time was found statistically insignificant having p value greater than 0.05. The coefficient of determination (R2=0.930) shows that % adsorption is highly dependent on the studied factors and their interactions. Under the optimized set of conditions, high absorption capacity of 200.22 mg g-1 was achieved.

Application of mesoporous nanofibers as sorbent for removal of veterinary drugs from water systems

A novel environmentally benign method was developed for the simultaneous removal of sulphonamides and multiclass class of veterinary drugs using mesoporous nanofibers. Processing parameters which affect the removal efficiency, such as pH, initial analyte concentration, adsorbent dosage and contact time were studied. An optimised method was applied to a real wastewater samples collected from Daspoort Wastewater Treatment Plant (WWTP), South Africa. Under optimum conditions, the removal efficiency of veterinary drugs from effluent and influent ranged from 35.24–94.57 ± 0.24 and 31.71–76.91 ± 0.65 mg g−1, respectively. The surface area, cumulative volume of pores and average pore diameter of the nanofibers were determined as 2402.62 ± 13.62 m2 g−1, 2.04 cm3 g−1 and 3.39 nm, respectively. The maximum adsorption capacity was ranged from 166 to 1000 mg g−1. The adsorption kinetics obeyed the pseudo-second-order rate equation suggesting that particle diffusion was the rate-limiting mechanism for adsorption of veterinary drugs on electrospun nanofibers.

Synthesis of Z-Scheme heterojunction ZnNb2O6/g-C3N4 nanocomposite as a high efficient photo-catalyst for the degradation of 2,4-DCP under simulated sunlight

In view of the deterioration of the environment and the shortage of resources, it is necessary to develop efficient photocatalysts for the degradation of organic pollutants. Herein, a novel and environmentally friendly ZnNb2O6/g-C3N4 heterojunction nanocomposite was synthesized by calcination-hydrothermal method successfully. The chemical and physical capabilities of the material were characterized by various kinds of analytical instruments. Compared with ZnNb2O6 and g-C3N4, ZnNb2O6/g-C3N4 showed the strongest photocatalytic activity. The nanomaterial was used in the removal of the pollutant 2,4-DCP. The effects of degradation conditions were discussed including component ratio, material dosage, initial analyte concentration, pH and salinity. After 180 min’ simulated sunlight illumination, the removal efficiency of 2,4-DCP (10 mg/L) reached 95.7% under the optimum condition. Furthermore, the possible photocatalytic mechanisms were discussed according to four aspects: (i) The conformation of the active species; (ii) The calculation of valence and conduction band; (iii) The analysis Z-scheme heterojunction mechanism; (iv) The speculation of feasible photocatalytic paths. In conclusion, the ZnNb2O6/g-C3N4 (ZC-7) nanocomposite has the least recombination rate of electron-hole pairs and the highest photocatalytic efficiency.

Ion-exchange Extraction of Palladium(II) from Chloride Solutions Using a Silica Gel-Immobilized Imidazolium Salt

ABSTRACTSilica gel with covalently immobilized imidazolium group was obtained by click reaction and characterized by elemental analysis, thermogravimetry, as well as by IR and solid-state 13C NMR spectroscopy. The total exchange capacity of the obtained material was calculated to be 0.26 ± 0.02 mM/g. The nature of the salt background of KCl and HCl was shown to have effect on the distribution coefficients of Cu(II), Ni(II), Co(II), Cd(II), and Pd(II) on modified silica gel. In the case of Pd(II) possessing a high distribution coefficient under selected steady-state ion-exchange conditions (0.1 M HCl), dynamic breakthrough curves were obtained for different levels of initial analyte concentration. The addition of equimolar amounts of Fe(III), Al(III), Cu(II), Ni(II), Co(II), and Zn(II) and a change in the total salinity level up to 35 g/L were shown to have no effect on the distribution coefficient of Pd(II) under dynamic ion exchange conditions.

Removal of Multi-Class Antibiotic Drugs from Wastewater Using Water-Soluble Protein of Moringa stenopetala Seeds

The removal of ten selected antibiotic drugs belonging to different classes (sulphonamides, fluoroquinolones, macrolides, and tetracycline) was investigated using water-soluble proteins from the seeds of Moringa stenopetala. The surface functional groups of water-soluble protein powder before and after removal of antibiotics were characterized using Fourier transform infrared (FTIR). Processing parameters that could affect the removal efficiency, such as initial analyte concentration, protein dosage, and pH were studied. An optimized method was applied to a real wastewater sample collected from Daspoort Wastewater Treatment Plant (WWTP) located in Pretoria, South Africa. Under optimal conditions, the results indicated good agreement between the efficiency of water-soluble proteins to remove antibiotics from the real wastewater sample and from the synthetic wastewater sample prepared in the laboratory using standard solutions with known concentrations. The percentage of removal under optimum conditions (protein dosage of 40 mg, initial analyte concentration of 0.1 mg L−1, and pH 7) was between 85.2 ± 0.01% and 96.3 ± 0.03% for standard mixture solution and from 72.4 ± 0.32% to 92.5 ± 0.84% and 70.4 ± 0.82% to 91.5 ± 0.71% for the real wastewater (effluent and influent) sample.

New Concepts for the Determination of Oxidation Efficiencies in Liquid Chromatography-Isotope Ratio Mass Spectrometry.

In liquid chromatography coupled to isotope ratio mass spectrometry (LC-IRMS), analytes are separated on an LC system and consecutively oxidized to CO2, which is required for the determination of compound-specific carbon isotope ratios. Oxidation is performed in an online reactor by sulfate radicals. Reaction conditions in the interface depend on the flow conditions determined by the LC method and the flow rates and concentrations of oxidation agent and phosphoric acid added in the interface. To determine accurate isotope ratios, a quantitative conversion of the carbon contained in the analyte to the CO2 measurement gas is a prerequisite. Oxidation efficiencies are not commonly evaluated during method development, although certain analytes are known to be difficult to be oxidized by sulfate radicals. For the assessment of the oxidation efficiency of the LC-IRMS system, three different approaches were evaluated. (1) Residual organic carbon in the eluent stream of the interface was determined to calculate oxidation yields depending on the initial analyte concentration. (2) The IRMS response was calibrated to an inorganic carbon reference material to determine oxidation efficiencies with the help of the IRMS as a detector. (3) The oxidation temperature was deliberately reduced while monitoring the δ13C and signal intensity. The common assumption that a linear relation of IRMS signal to analyte concentration is an indicator for complete oxidation in LC-IRMS could be disproved. All three approaches can be applied for future method development in LC-IRMS, monitoring of existing flow injection applications, as well as for verification of complete oxidation in established LC-IRMS methods.

Immunoaffinity microcryogels for purification of transferrin

Immunoaffinity chromatography has a huge interest in the biomedical and biotechnological fields, in particular for one-step isolation, purification and removal of analyte compounds. In this study, uniform-sized microcryogels, a new type of cryogels, were synthesized using 2-hydroxyetyhl methacrylate and epoxy-group-containing monomer, glycidyl methacrylate for purification of a plasma protein, transferrin. Immunoaffinity microcryogels containing anti-Tf antibodies were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy, optical microscopy, scanning electron microscopy, density measurements and swelling tests. Adsorption studies in aqueous media were carried out in order to examine the effects of medium pH, initial concentration of analyte and contact time. It was found that the optimum pH was 6.0 and the maximum adsorption capacity of immunoaffinity microcryogels at this pH value found to be 9.82 mg/g. The KL constant for Langmuir isotherm was calculated as 2.65 mL/mg. The maximum adsorption capacity obtained from experimental studies is also very close to the calculated Langmuir adsorption capacity (11.27 mg/g). Langmuir adsorption isotherms and pseudo-second-order kinetic models are consistent with the adsorption process, which means that the adsorption is single layered and chemically controlled. The purity of the eluted hsTf from plasma was about 84% with yield about 82%. After the tenth use of the same microcryogels, the maximum hsTf adsorption capacity decreased by about 20%. The results indicated that the immunoaffinity microcryogels having anti-Tf antibody ligands could be a safe and cost-friendly method for purification of transferrin.