Urea-Induced Dissociation of Nerve Growth Factor from Venom of Chinese Cobra by SEC

The urea-induced dissociation of nerve growth factor from venom of Chinese cobra (_cNGF) was studied by intrinsic fluorescence emission spectra, SEC, urea-gradient polyacrylamide gel electrophoresis, assays of biological activity and thermodynamic parameters. The results showed that when urea concentration was lower than or equal to 4.0 mol L⁻¹ or higher than or equal to 8.0 mol L⁻¹, _cNGF existed only in native homodimer form or monomer form, respectively; whereas when urea concentration was higher than 4.0 mol L⁻¹ and lower than 8.0 mol L⁻¹, they existed simultaneously in the native homodimer and monomer forms and the former decreased, while the latter increased with the increase in urea concentration. Based on the association–dissociation equilibrium between _cNGF and urea molecules, an equation, which includes two characteristic dissociation parameters K and ∆m, was presented to describe the urea-induced dissociation process of _cNGF. As the reaction temperature increased from 15 to 35 °C, positive enthalpy and entropy changes were observed, and the parameter K increased from 2.72 × 10⁻¹³ to 5.18 × 10⁻¹² (L mol⁻¹), while the parameters ∆m and ∆G, respectively, decreased from 10.18 to 8.42 and from −10.27 to −18.67 (kJ mol⁻¹), which means that the urea-induced dissociation of _cNGF was spontaneous and entropy-driven and the higher temperature was favorable for the dissociation process. Using the procedures and equations mentioned in the paper, the urea-induced dissociation of _cNGF is first comprehensively described. Furthermore, this work presents a useful method for people to study the dissociation of dimer or multimer proteins induced by denaturants, inducers, pH, etc.

     

RP-LC Determination of Residual Monomers in Polycarboxylate Superplasticizers

A procedure was developed for the determination of residual monomers in polycarboxylate superplasticizer by reversed-phase high performance liquid chromatography. Seven kinds of residual monomers were quantitatively determined on a SinoChrom ODS-BP (C18) column and UV detector at 205 nm. The mobile phases which were used to determine micromolecular monomers were composed of acetonitrile and phosphate buffer solution (0.05 mol L^?1, pH = 3) in the ratio of 8:92 (v/v). While the mobile phases for long side-chain monomers testing were composed of acetonitrile and phosphate buffer solution (0.05 mol L^?1, pH = 6.5) in the ratio of 40:60 (v/v). The linear response ranged from 4.0 × 10^?6?C2.0 × 10^?3 mol L^?1. The detection limit was 0.12 × 10^?5?C0.8 × 10^?5 mol L^?1. Determination of real samples showed that relative standard deviation of high conversion rate samples was 3.1?C8.7% and standard addition recovery ratio was 91.5?C102.8%. While the relative standard deviation of low conversion rate samples was less than or close to 1% and the standard addition recovery ratio was 96.3?C103.1%.     

Study on thermodynamic properties of glyphosate by oxygen-bomb calorimeter and DSC

The combustion enthalpy of glyphosate was determined by XRY-1C oxygen-bomb calorimeter at a constant volume. The standard mole combustion enthalpy and the standard mole formation enthalpy have been calculated to be ?1702.19 and ?1478.36 kJ mol^?1, respectively. For testing the reliability of instrument, glycine and naphthalene were used as reference materials by comparing the measured values with the literature values, the absolute error and relative error are 2.58 kJ mol^?1 and 0.26 % for glycine, respectively, and these of naphthalene are 4.08 kJ mol^?1 and 0.08 %, respectively. Moreover, the constant-pressure heat capacities c _p of glyphosate were measured by differential scanning calorimetry in the temperature range 303.15–365.15 K, and the relationship between c _p and temperature was established. These related studies can provide a thermodynamic basis for their further application.     

Sensitive determination of the endocrine disruptor bisphenol A at ultrathin film based on nanostructured hybrid material SiO<Subscript>2</Subscript>/GO/AgNP

In this work, we described an electrochemical sensor using a nanocomposite based on graphene oxide (GO), silver nanoparticles (AgNP), and disordered mesoporous silica (SiO₂), which was used for the determination of bisphenol A in water samples. Initially, the hybrid material SiO₂/GO was synthesized via sol-gel process, subsequently decorated with AgNP with an approximate 20 nm particle size prepared directly on the surface of the SiO₂/GO using N, N-dimethylformamide (DMF) as an agent reducer. A glassy carbon electrode was modified with SiO₂/GO/AgNP and used in developing a sensitive electrochemical sensor for the determination of bisphenol A in phosphate buffer 0.1 mol L^?1 (pH 7.0). The detection limit was 45.2 nmol L^?1 with a linear response range between 1.0 × 10^?7 and 2.6 × 10^?6 mol L^?1 and a sensitivity of 1.27 × 10^?7 A mol^?1 L. Finally, the optimized electrochemical sensor was used for the quantitation of endocrine interfering in natural waters.     

Electrochemical Responses and Sensitivities of Films Based on Multi-Walled Carbon Nanotubes in Aqueous Solutions

Novel films consisting of multi-walled carbon nanotubes (MWCNTs) were fabricated by means of chemical vapor deposition with decomposition of either acetonitrile (ACN) or benzene (BZ) using ferrocene as catalyst. The electrochemical responses of MWCNT-based films towards the ferrocyanide/ferricyanide, [Fe(CN)₆]^3?/4? redox couple were probed by means of cyclic voltammetry and electrochemical impedance spectroscopy at 25.0?±?0.5?°C. Both MWCNT-based films exhibit Nernstian response towards [Fe(CN)₆]^3?/4? with some slight kinetic differences. Namely, heterogeneous electron transfer rate constants lying in ranges of 2.69?×?10^?2?C1.7?×?10^?3 and 9.0?×?10^?3?C2.6?×?10^?3?cm·s^?1 were obtained at v?=?0.05?V·s^?1 for MWCNT_ACN and MWCNT_BZ, respectively. The detection limit of MWCNT_ACN, estimated to be about 4.70?×?10^?7?mol·L^?1 at v?=?0.05?V·s^?1, tends to become slightly poorer with the increase of the scan rate, namely at v?=?0.10?V·s^?1 the detection limit of 1.70?×?10^?6?mol·L^?1 was determined. Slightly poorer response ability was exhibited by MWCNT_BZ; specifically the detection limits of 1.57?×?10^?6 and 4.35?×?10^?6?mol·L^?1 were determined at v?=?0.05 and v?=?0.10?V·s^?1, respectively. The sensitivities of MWCNT_ACN and MWCNT_BZ towards [Fe(CN)₆]^3?/4? were determined as 1.60?×?10^?7 and 1.51?×?10^?7?A·L·mol^?1·cm^?2, respectively. The excellent electrochemical performance of MWCNT_ACN is attributed to the presence of incorporated nitrogen in the nanotube??s structure.     

Development and validation of HTS assay for screening the calcium-activated chloride channel modulators in TMEM16A stably expressed CHO cells

Calcium-activated chloride channels (CaCCs), for example TMEM16A, are widely expressed in a variety of tissues and are involved in many important physiological functions. We developed and validated an atomic absorption spectroscopy (AAS)-based detection system for high-throughput screening (HTS) of CaCC modulators. With this assay, Cl^? flux from CHO cells stably transfected with TMEM16A is assayed indirectly, by measuring excess silver ions (Ag⁺) in the supernatant of AgCl precipitates. The screening process involved four steps: (1) TMEM16A CHO cells were incubated in high-K⁺ and high-Cl^? buffer with test compounds, and with ionomycin as Ca²⁺ ionophore, for 12 min; (2) cells were washed with a low-K⁺, Cl^?-free and Ca²⁺-free buffer; (3) CaCC/TMEM16A were activated in high-K⁺, Cl^?-free buffer with ionomycin (10 μmol L^?1) for 12 min; and (4) excess Ag⁺ concentration was measured using an ion channel reader (ICR, an AAS system). The assay can be used to screen CaCC activators and inhibitors at the same time. With this assay, positive control drugs, including NPPB, CaCCinh-A01, flufenamic acid (Flu) and E_act, all had good concentration-dependent effects on CaCC/TMEM16A. NPPB and CaCCinh-A01 inhibited the CaCC/TMEM16A currents completely at 300 μmol L^?1, with IC₅₀ values of 39.35?±?4.72 μmol L^?1 and 6.35?±?0.27 μmol L^?1, respectively; and E_act, activated CaCC/TMEM16A, with an EC₅₀ value of 3.92?±?0.87 μmol L^?1.     

Mechanism of Oxidation of Ketorolac by Hexacyanoferrate(III) in Aqueous Alkali: A Thermodynamics and Kinetics Study

The kinetics of the oxidation of ketorolac by hexacyanoferrate(III) (HCF) in aqueous alkaline medium at a constant ionic strength of 0.75 mol·dm^?3 was studied spectrophotometrically at 300 K. A plausible mechanism was proposed and the rate law was derived. The mechanism of oxidation of ketorolac (KET) in alkaline medium has been shown to proceed via a KET-HCF complex, which decomposes in a slow step followed by other fast steps to give the products. The main oxidative product was identified as (2,3-dihydro-1-hydroxy-1H-pyrrolizin-5-yl-)(phenyl)methanone and is characterized by its LC–ESI–MS spectrum. Thermodynamic parameters of various equilibria of the mechanism were calculated and activation parameters ΔH ^≠, ΔS ^≠, ΔG ^≠ and log₁₀ A were found to be 29.9 kJ·mol^?1, ?220 J·K^?1·mol^?1, 96 kJ·mol^?1 and 2.70 respectively.     

Evaluation of a novel composite based on functionalized multi-walled carbon nanotube and iron phthalocyanine for electroanalytical determination of isoniazid

A novel platform for electroanalysis of isoniazid based on graphene-functionalized multi-walled carbon nanotube as support for iron phthalocyanine (FePc/f-MWCNT) has been developed. The FePc/f-MWCNT composite has been dropped on glassy carbon forming FePc/f-MWCNT/GC electrode, which is sensible for isoniazid, decreasing substantially its oxidation potential to +200 mV vs Ag/AgCl. Electrochemical and electroanalytical properties of the FePc/f-MWCNT/GC-modified electrode were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electrochemical microscopy, and amperometry. The sensor presents better performance in 0.1 mol L^?1 phosphate buffer at pH 7.4. Under optimized conditions, a linear response range from 5 to 476 μmol L^?1 was obtained with a limit of detection and sensitivity of 0.56 μmol L^?1 and 0.023 μA L μmol^?1, respectively. The relative standard deviation for 10 determinations of 100 μmol L^?1 isoniazid was 2.5%. The sensor was successfully applied for isoniazid selective determination in simulated body fluids.     

Voltammetric determination of mesalazine in pharmaceutical preparations and biological samples using boron-doped diamond electrode

Voltammetric method for the determination of non-steroidal anti-inflammatory drug mesalazine (5-ASA) is presented for the first time using boron-doped diamond electrode (BDDE). 5-ASA provides one well-developed SWV oxidation peak at about ?900 mV (vs. saturated silver/silver chloride reference electrode) on BDDE. Britton-Robinson buffer (pH 7.0) was chosen as an optimal supporting electrolyte for the determination of 5-ASA using square wave voltammetry (SWV). Parameters of SWV were developed and low limit of detection (7.0 × 10^?7 mol L^?1) was reached. In addition, relative standard deviation of repeated measurements (c _5-ASA = 5 × 10^?5 mol L^?1, RSD_M = 2.7%) and relative standard deviation of repeated determinations (RSD_D < 1.5%) were calculated and confirm obtained good results. Applicability of the proposed method was verified by an analysis of a pharmaceutical preparation and spiked human urine.     

Effect of Organic Loading Rate and Fill Time on the Biohydrogen Production in a Mechanically Stirred AnSBBR Treating Synthetic Sucrose-Based Wastewater

This study investigated the feasibility to produce biohydrogen of a mechanically stirred anaerobic sequencing batch biofilm reactor (AnSBBR) treating sucrose-based synthetic wastewater. The bioreactor performance (30 °C) was evaluated as to the combined effect of fill time (2, 1.5, and 1 h), cycle length (4, 3, and 2 h), influent concentration (3,500 and 5,250 mg chemical oxygen demand (COD)?L^?1) and applied volumetric organic load (AVOL_CT from 9.0 to 27.0 g COD L^?1 d^?1). AVOLs were varied according to influent concentration and cycle length (t _C). The results showed that increasing AVOL_CT resulted in a decrease in sucrose removal from 99 to 86 % and in improvement of molar yield per removed load (MYRL_S.n) from 1.02 mol H₂?mol carbohydrate^?1 at AVOL_CT of 9.0 g COD L^?1 d^?1 to maximum value of 1.48 mol H₂?mol carbohydrate^?1, at AVOL_CT of 18.0 g COD L^?1 d^?1, with subsequent decrease. Increasing AVOL_CT improved the daily molar productivity of hydrogen (MPr) from 15.28 to 49.22 mol H₂?m^?3 d^?1. The highest daily specific molar productivity of hydrogen (SMPr) obtained was 8.71 mol H₂?kg TVS^?1 d^?1 at an AVOL_CT of 18.0 g COD L^?1 d^?1. Decreasing t _C from 4 to 3 h decreased sucrose removal, increased MPr, and improved SMPr. Increasing influent concentration decreased sucrose removal only at t _C of 2 h, improved MYRL_S,n and MPr at all t _C, and also improved SMPr at t _C of 4 and 3 h. Feeding strategy had a significant effect on biohydrogen production; increasing fill time improved sucrose removal, MPr, SMPr, and MYRL_S,n for all investigated AVOL_CT. At all operational conditions, the main intermediate metabolic was acetic acid followed by ethanol, butyric, and propionic acids. Increasing fill time resulted in a decrease in ethanol concentration.     

Molecular imprinting polymer electrosensor based on gold nanoparticles for theophylline recognition and determination

An electrochemical sensor for theophylline (ThPh) was prepared by electropolymerizing o-phenylenediamine on a glassy carbon electrode in the presence of ThPh via cyclic voltammetry, followed by deposition of gold nanoparticles using a potentiostatic method. The effects of pH, ratio between template molecule and monomer, number of cycles for electropolymerization, and of the solution for extraction were optimized. The current of the electro-active model system hexacyanoferrate(III) and hexacyanoferrate(IV) decreased linearly with successive addition of ThPh in the concentration range between 4.0?×?10^?7?~?1.5?×?10^?5 mol·L^?1 and 2.4?×?10^?4?~?3.4?×?10^?3 mol·L^?1, with a detection limit of 1.0?×?10^?7 mol·L^?1. The sensor has an excellent recognition capability for ThPh compared to structurally related molecules, can be regenerated and is stable.

Voltammetric determination of 17α-ethinylestradiol hormone in supply dam using BDD electrode

In this work, a simple method for electroanalytical determination of 17α-ethinylestradiol (EE2) hormone in natural waters was developed using a boron-doped diamond electrode (BDD). The analyses were performed using square wave voltammetry and the parameters were optimized. The results showed a well-defined irreversible oxidation peak (BR buffer 0.1 mol L^?1, pH 8.0) at +0.65 V (vs. Ag/AgCl). The voltammetric results showed also that the oxidation process is controlled by adsorption of species and indicated that there are two electrons involved. The obtained analytical curves for 17α-ethinylestradiol presented good linearity in the concentration range 9.9?×?10^?7 to 5.2?×?10^?6 mol L^?1 in utlrapure water and 7.9?×?10^?7 to 5.2?×?10^?6 mol L^?1 in natural water samples (supply dam). Detection limits (DL) obtained were between 2.4?×?10^?7 and 7.5?×?10^?7 mol L^?1 and quantification limits (QL) between 7.9?×?10^?7 and 2.5?×?10^?6 mol L^?1. The recovery experiments showed values between 86 and 114 % for spiked samples thus indicating the applicability of the electroanalytical methodology to quantify 17α-ethinylestradiol directly in natural water of supply Dam (Billings Dam in Diadema-SP. Brazil), without any preconcentration or derivatization.     

Removal of lead from aqueous solutions by adsorption with surface precipitation

An activated carbon from Coconut (Cocos nucifera) shells was prepared by physical activation with carbon dioxide and water vapor. The activated carbon obtained has a surface area of 1058 m² g^?1 and such a high micropore volume of 0.49 cm³ g^?1. This carbon was studied for the removal of lead from water. Sorption studies were performed at 30 °C, at different pH and adsorbent doses, in batch mode. Lead precipitation was observed on the surface of the activated carbon. Maximum adsorption occurred at pH 9 for an adsorbent dose of 2 g L^?1. Kinetic studies, at the initial concentration of 150 mg L^?1 of lead, pH 5 and an adsorbent dose of 1 g L^?1, yielded an equilibrium time of 50 h for this activated carbon. The kinetic data were modeled with the pseudo first order, the pseudo second order and the Bangham models. The pseudo second order model fitted the data well. The sorption rate constant (7 × 10^?4 mol^?1 Kg s^?1) and the maximum amount of lead adsorbed (0.23 mol kg^?1) are quite good compared to the data found in literature. Sorption equilibrium studies were conducted in a concentration range of lead from 0 to 150 mg L^?1. In an aqueous lead solution with an initial concentration of 30 mg L^?1, at pH 5, adsorbent dose 1 g L^?1, activated Coconut shell carbon removed at equilibrium 100 % of the heavy metal. The equilibrium data were modeled with the Langmuir and Freundlich equations, of which the former gave the best fit. The Langmuir constants Q_{max eq} (0.23 mol kg^?1) and K_L (487667 L mol^?1) are in good agreement with literature. XPS studies identified adsorbed species as lead carbonates and/or lead oxalates and precipitates as lead oxide and/or lead hydroxide on the activated carbon surface. The Coconut shell activated carbon is a very efficient carbon due to its high surface area, to the presence of many micropores on its surface and to the presence surface groups like hydroxyls promoting adsorption in the porous system and lead crystal precipitation on the activated carbon surface.     

Biodiesel Residual Glycerol Metabolism by Klebsiella pneumoniae: Pool of Metabolites Under Anaerobiosis and Oxygen Limitation as a Function of Feeding Rates

The metabolism of residual glycerol from biodiesel synthesis by Klebsiella pneumoniae BLh-1 was investigated in this study. Batch and fed-batch cultivations were performed in bioreactors under anaerobic and oxygen limitation conditions. Results of batch cultivations showed that the main product was 1,3-propanediol (1,3-PD) in both conditions, although the higher yields and productivities (0.46 mol mol^?1 glycerol and 1.22 g?L^?1?h^?1, respectively) were obtained under anaerobic condition. Large amounts of ethanol were also produced under batch anaerobic condition, peaking at 12.30 g?L^?1. Batch cultivations under oxygen limitation were characterized by faster growth kinetics, with higher biomass production but lower conversions of glycerol into 1,3-PD, with yields and productivities of 0.33 mol mol^?1 glycerol and 0.99 g?L^?1?h^?1, respectively. The fed-batch cultivations were carried out in order to investigate the effects of feeding of raw glycerol on cells. Fed-batch under anaerobiosis showed that 1,3-PD and ethanol concentrations increased with the feeding rate, with maximal productions of 26.12 and 19.2 g?L^?1, respectively. The oxygen limitation conditions diverted the bacterium metabolism to an elevated lactic acid formation, reaching 59 g?L^?1 in higher feeding rates of glycerol, but lowering the production of ethanol.     

Highly sensitive electrocatalytic determination of pyrazinamide using a modified poly(glycine) glassy carbon electrode by square-wave voltammetry

A new voltammetric sensor based on electropolymerization of glycine at glassy carbon electrode (GCE) was developed and applied to determine of pyrazinamide (PZA) by square-wave voltammetry (SWV). The initial cyclic voltammetric studies showed an electrocatalytic activity of poly(Gly)/GCE on redox system of pyrazinamide in 0.1 mol L^?1 phosphate buffer solution pH 7.5, with E _Pc and E _Pa in ?0.85 and ?0.8 V (versus E _Ag/AgCl), respectively. Studies at different scan rates suggest that the redox system of pyrazinamide at poly(Gly)/GCE is a process controlled by diffusion in the interval from 10 to 100 mV s^?1. Square-wave voltammetry-optimized conditions showed a linear response of PZA concentrations in the range from 0.47 to 6.15 μmol L^?1 (R?=?0.998) with a limit of detection (LOD) of 0.035 μmol L^?1 and a limit of quantification (LOQ) of 0.12 μmol L^?1. The developed SWV-poly(Gly)/GCE method provided a good intra-day (RSD?=?3.75 %) and inter-day repeatability (RSD?=?4.96 %) at 4.06 μmol L^?1 PZA (n?=?10). No interference of matrix of real samples was observed in the voltammetric response of PZA, and the method was considered to be highly selective for the compound. In the accuracy test, the recovery was found in the range of 98.2 and 104.0 % for human urine samples and pharmaceutical formulation (tablets). The PZA quantification results in pharmaceutical tablets obtained by the proposed SWV-poly(Gly)/GCE method were comparable to those found by official analytical protocols.     

pH-controlled morphological structure and electrochemical performances of polyaniline/nickel hexacyanoferrate nanogranules during electrochemical deposition

To explore the dependences of morphology and electrochemical performance of polyaniline/nickel hexacyanoferrate (PANI/NiHCF) nanogranules on pH value of the reaction system, electrodeposition of PANI/NiHCF nanogranules was performed across a pH range from 0 to 7 on carbon nanotubes (CNTs)-modified platinum substrate by cyclic voltammetry in a mixture of 0.002 mol L^?1 NiSO₄, 0.25 mol L^?1 Na₂SO₄, 0.002 mol L^?1 K₃Fe(CN)₆, and 0.01 mol L^?1 aniline solutions. The morphology and structure of PANI/NiHCF nanogranules were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The supercapacitive performances of the nanogranules were investigated with cyclic voltammetry (CV), charge/discharge tests, and electrochemical impedance spectroscopy (EIS). The results showed that the nanogranules with different morphology and sizes were obtained with the change of pH values from 0 to 7, which could control the mechanism of homogeneous or heterogeneous nucleation directly. The nanogranules were dispersed in matrix uniformly at pH 0 and pH 1, while the size of which decreased with the increase of pH values. The smooth cross-linking network structure was found from pH 2 to 7. The structure of PANI/NiHCF nanogranules had slightly changed from pH 0 to 7. PANI/NiHCF nanogranules had good electrochemical performance from pH 0 to 7 in a mixture of 0.5 mol L^?1 H₂SO₄ and 0.5 mol L^?1 KNO₃ solutions, and the highest specific capacitance value of 274 F g^?1 was obtained at current densities of 2 mA cm^?2 in neutral medium. PANI/NiHCF nanogranules had high stability in neutral medium after 2,000 cycles by CV.     

Simultaneous Analysis of Sugars and Polyphenols in Tobacco by CZE with Amperometric Detection Based on a Cu2O/MWCNT-COOH Composite Electrode

A composite electrode was fabricated from Cu₂O powder, carboxyl-functionalized multi-wall carbon nanotubes (MWCNT-COOH), and paraffin oil in the proportions 51:17:32 (w/w). This composite electrode was used for amperometric detection (CZE–AD) in simultaneous capillary zone electrophoretic analysis of chlorogenic acid, rutin, sucrose, glucose, mannose, and fructose in tobacco samples. Under the optimum conditions, the six analytes could be separated in 100 mmol L^?1 NaOH buffer within 30 min. Good linearity was achieved in the range 1 × 10^?7–1 × 10^?4 mol L^?1 for the two polyphenols and 5 × 10^?6–1 × 10^?3 mol L^?1 for the four sugars. The detection limits (S/N = 3) for the polyphenols and sugars were as low as 10^?8 mol L^?1 and 10^?6 mol L^?1, respectively.     

Zur Thermochemie der Zinnhalogenide

The enthalpy change of the reaction at 298 K between Br₂ (l) and Sn(c) in CS₂ as solvent giving SnBr₄ (s) has been determined by calorimetry to be (?374, 2±1.4) kJ·mol^?1, [(?89.45±0.33) kcal·mol^?1]. By the same method the heat of solution of SnBr₄ (c) in CS₂ has been found to be (11.9±0.3) kJ·mol^?1, [(2.84±0.08) kcal·mol^?1]. Combining these results, a value of (?386.1±1.5) kJ·mol^?1, [(?92.3±0.4) kcal·mol^?1] is derived for the standard heat of formation of SnBr₄ (c). Substituting this figure in the thermochemical cycle hitherto used for calculating the heat of formation of SnBr₄ (c) gives ?124.3 kcal·mol^?1 for the standard heat of formation of SnCl₄ (l), which is in reasonable agreement with a recent determination of this quantity⁸.     

Effect of surfactants on the performance of hollow fiber renewal liquid membrane (HFRLM): a case study of uranium transfer

In this study the application of various surfactant agents on the performance of HFRLM for uranium transfer was investigated. Using Taguchi experimental design in recycling mode of HFRLM, maximum uranium recovery of 63.17% was obtained at 0.15 mol L^?1 H₂SO₄, 0.0125 mol L^?1 Alamine 336 and 0.25 mol L^?1 NH₄Cl in the donor, liquid membrane and acceptor phase, respectively. Also, the continuous mode experiments were conducted and HFRLM stability was compared with HFSLM. The uranium transfer would be improved by adding 0.05 mmol L^?1 of SDS, CTAB and LAE-7 to the donor phase and 10 mmol L^?1 of CTAB and LAE-7 to the acceptor phase.     

Rapid voltammetric determination of maltol in some foods and beverages using a poly(methylene blue)/graphene-modified glassy carbon electrode

A novel poly(methylene blue)/graphene composite glassy carbon electrode was fabricated and the electrochemical behavior of maltol at the modified electrode was studied by cyclic voltammetry. In phosphate-buffered solution, the modified electrode exhibited excellent electrocatalytic activity towards the electrochemical oxidation of maltol. Under optimized conditions, the oxidation peak current showed a linear relationship with the concentrations of maltol in the ranges of 8.00?×?10^?7 to 4.00?×?10^?5 and 4.00?×?10^?5 to 5.40?×?10^?4 mol L^?1, with a detection limit of 6.50?×?10^?8 mol L^?1. The performance of the developed method was validated in terms of linearity (r?=?0.9981 and 0.9955), recovery (97.0?99.3 %), reproducibility (relative standard deviations?≤?3.1 %, n?=?6), and robustness. The method shows excellent sensitivity, selectivity, and reproducibility and has been successfully applied to analyzing maltol in a wide variety of food products.