Showing papers on "Buffer solution published in 2007"
TL;DR: In this paper, the performance of cloth electrode assemblies (CEA) with bicarbonate buffer solutions was evaluated using a facilitated proton transfer mechanism for MFCs in the presence of pH buffers.
Abstract: Phosphate buffer solution has been commonly used in MFC studies to maintain a suitable pH for electricity-generating bacteria and/or to increase the solution conductivity. However, addition of a high concentration of phosphate buffer in MFCs could be expensive, especially for wastewater treatment. In this study, the performances of MFCs with cloth electrode assemblies (CEA) were evaluated using bicarbonate buffer solutions. A maximum power density of 1550 W/m3 (2770 mW/m2) was obtained at a current density of 0.99 mA/cm2 using a pH 9 bicarbonate buffer solution. Such a power density was 38.6% higher than that using a pH 7 phosphate buffer at the same concentration of 0.2 M. Based on the quantitative comparison of free proton transfer rates, diffusion rates of pH buffer species, and the current generated, a facilitated proton transfer mechanism was proposed for MFCs in the presence of the pH buffers. The excellent performance of MFCs using bicarbonate as pH buffer and proton carrier indicates that bicarbon...
302 citations
TL;DR: In this article, a novel polyelectrolyte hydrogels (coded as GA) based on cationic guar gum (CGG) and acrylic acid monomer by photoinitiated free-radical polymerization were synthesized with various feed compositions.
241 citations
TL;DR: Fluorescence correlation spectroscopy measurements indicate that nanocrystals easily form aggregates when the buffer pH is changed and this tendency is reduced when the surface of the diamonds is covered with surfactants.
Abstract: The fluorescence and motional dynamics of single diamond nanocrystals in buffer solution and in living cells is investigated. Stable hydrosols of nanodiamonds in buffer solutions are investigated by fluorescence correlation spectroscopy. Measurement of the effective hydrodynamic radius yields particles of 48 nm diameter, which is in excellent agreement with atomic force microscopy measurements made on the same particles. Fluorescence correlation spectroscopy measurements indicate that nanocrystals easily form aggregates when the buffer pH is changed. This tendency is reduced when the surface of the diamonds is covered with surfactants. Upon incubation, cells spontaneously take up nanocrystals that uniformly distribute in cells. Most of the particles get immobilized within a few minutes. The binding of streptavidin to biotinylated aggregates of 4 nm diameter nanodiamonds is demonstrated.
231 citations
TL;DR: Results show that semi-IPN hydrogel seems to be of great promise in pH-temperature oral drug delivery systems.
202 citations
TL;DR: In this paper, the passivity of AISI 304L and 316L stainless steels in a borate buffer solution, with and without the addition of chloride ions, was studied using cyclic voltammetry and potentiodynamic measurements.
198 citations
TL;DR: Ultraviolet-visible and Fourier transform infrared spectroscopy studies showed that Hb immobilized in the Nafion/nano-CaCO3 film still remained its native arrangement, and the Hb modified electrode showed an excellent electrocatalytic behavior to the reduction of H2O2, trichloroacetic acid (TCA), and NaNO2.
Abstract: Room temperature ionic liquid N-butylpyridinium hexafluorophosphate (BPPF6) was used as a binder to construct a new carbon ionic liquid electrode (CILE), which exhibited enhanced electrochemical behavior as compared with the traditional carbon paste electrode with paraffin. By using the CILE as the basal electrode, hemoglobin (Hb) was immobilized on the surface of the CILE with nano-CaCO3 and Nafion film step by step. The Hb molecule in the film kept its native structure and showed good electrochemical behavior. In pH 7.0 Britton−Robinson (B−R) buffer solution, a pair of well-defined, quasi-reversible cyclic voltammetric peaks appeared with cathodic and anodic peak potentials located at −0.444 and −0.285 V (vs SCE), respectively, and the formal potential (E°‘) was at −0.365 V, which was the characteristic of Hb Fe(III)/Fe(II) redox couples. The formal potential of Hb shifted linearly to the increase of buffer pH with a slope of −50.6 mV pH-1, indicating that one electron transferred was accompanied with o...
182 citations
TL;DR: The proposed procedure was successfully applied to detect adenosine and guanosine in human blood plasma and urine, without any preliminary pre-treatment, and showed excellent selectivity in the presence of hypoxanthine, xanthines, uric acid and ascorbic acid.
175 citations
TL;DR: In this article, a dual temperature and pH-sensitive comb-type grafted poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM)-co-AAc)) hydrogels were successfully prepared by grafting PNippAM chains with freely mobile ends onto the backbone of a cross-linked P(nipam-coAAc) network.
168 citations
TL;DR: In this article, the 15N/14N of NH4+ at natural abundance level in both freshwater and seawater was determined using colorimetric NO2- determination and a continuous flow purge and cryogenic trap system coupled to an isotope ratio mass spectrometer.
Abstract: We report a new method for determining the 15N/14N of NH4+ at natural abundance level in both freshwater and seawater. NH4+ is first quantitatively oxidized to NO2- by hypobromite (BrO-) at pH ∼ 12. After the addition of sodium arsenite to consume excess BrO-, yield is verified by colorimetric NO2- determination. NO2- is further reduced to N2O using a 1:1 sodium azide and acetic acid buffer solution using previously established procedures. The product N2O is then analyzed for isotopic composition using a continuous flow purge and cryogenic trap system coupled to an isotope ratio mass spectrometer. Reliable δ15N values (standard deviation is 0.3‰ or better) are obtained over an NH4+ concentration range of 0.5−10 μM using 20 mL volumes of either freshwater or seawater samples. Higher concentration samples are readily diluted to lower concentration. Preexisting NO2- is removed by treatment with sulfanilic acid. There is no interference from any of the nitrogen-containing compounds tested except short-chain a...
164 citations
TL;DR: The modified electrodes showed excellent catalytic activity, fast response time and high sensitivity toward oxidation of hydrazine in phosphate buffer solutions at pH range 4-8 and retained its initial response for at least 2 months if stored in dry ambient condition.
138 citations
TL;DR: A novel composite film modified glassy carbon electrode has been fabricated and characterized by scanning electron microscope (SEM) and voltammetry, and shows good stability, high accumulation efficiency and strong promotion to electron transfer.
TL;DR: The IL-CPE fabricated was sensitive, selective and showed good ability to distinguish the coexisting ascorbic acid and uric acid, which was successfully applied to the determination of DA injection samples.
Abstract: A room-temperature ionic liquid N-butylpyridinium hexafluorophosphate was used as a binder to construct an ionic liquid modified carbon paste electrode, which was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The ionic liquid carbon paste electrode (IL-CPE) showed enhanced electrochemical response and strong analytical activity towards the electrochemical oxidation of dopamine (DA). A pair of well-defined quasireversible redox peaks of DA appeared, with the redox peaks located at 215 mV (E
pa) and 151 mV (E
pc) (vs. the saturated calomel electrode, SCE) in pH 6.0 phosphate buffer solution. The formal potential (E
0´) was calculated as 183 mV (vs. SCE) and the peak-to-peak separation as 64 mV. The electrochemical behavior of DA on the IL-CPE was carefully investigated. Under the optimal conditions, the anodic peak currents increased linearly with the concentration of DA in the range 1.0 × 10−6–8.0 × 10−4 mol/L and the detection limit was calculated as 7.0 × 10−7 mol/L (3σ). The interferences of foreign substances were investigated and the proposed method was successfully applied to the determination of DA injection samples. The IL-CPE fabricated was sensitive, selective and showed good ability to distinguish the coexisting ascorbic acid and uric acid.
TL;DR: In comparison with conventional fluorimetric methods for detection of mercury ion, the present nanosensor is endowed with higher sensitivity and selectivity for Hg(II) in aqueous solution.
TL;DR: This work provides a simple and easy approach for selective determination of dopamine in the presence of ascorbic acid and uric acid using PEDOT-PANS film modified glassy carbon electrode.
TL;DR: The results shown that the methyl parathion and carbofuran can lead to competitive inhibition process of the enzyme, while diazinon and carbaryl act as mixed inhibitors.
TL;DR: In this paper, the influence of temperature, chloride ions and chromium element on the electronic property of passive film formed on carbon steel in NaHCO 3 /Na 2 CO 3 buffer solution is investigated by capacitance measurement and electrochemical impedance spectroscopy (EIS).
TL;DR: In this paper, direct electron transfer reactions of bilirubin oxidase at multi-walled carbon nanotube (MWCNT) modified glassy carbon electrodes (GCE) were reported.
TL;DR: PbS quantum dot lumophores emitting in the near-infrared are reported, which are stable for at least 5 days stored in physiologically relevant pH 6−8 buffer, have sub-10 nm hydrodynamic diameter, and exhibit 26% quantum yield.
Abstract: We report PbS quantum dot lumophores emitting in the near-infrared. The lumophores are stable for at least 5 days stored in physiologically relevant pH 6−8 buffer, have sub-10 nm hydrodynamic diame...
TL;DR: In this article, the mesoporous materials have been synthesized by co-condensation of bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPTS) and tetramETHoxysilane (TMOS) in acetic acid/sodium acetate buffer solution (HAc-NaAc, pH 4.4).
Abstract: The achievement of structural control over thioether-bridged mesoporous organosilicas is reported. The mesoporous materials have been synthesized by co-condensation of bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPTS) and tetramethoxysilane (TMOS) in acetic acid/sodium acetate buffer solution (HAc-NaAc, pH 4.4), using the nonionic surfactant P123 as a template. The mesostructure of the material is mainly controlled by the molar ratio of TESPTS/TMOS in the initial gel mixture. A mesophase transformation, progressing from a highly ordered 2D hexagonal structure via a vesiclelike structure to a mesostructured cellular foam, can be clearly observed when the molar ratio of TESPTS/TMOS is increased in increments. Solid-state NMR results show that TESPTS is not completely hydrolyzed and condensed at the applied buffer conditions. At low concentrations, the unhydrolyzed TESPTS can penetrate into the core of the surfactant micelles and change the packing parameter of the P123 surfactant. Above a certain concentration, the TESPTS can form a microemulsion with P123 surfactant molecules. Therefore, the vesiclelike structure or cellular foam structure can be synthesized by simply controlling the molar ratio of TESPTS/TMOS. This approach provides a novel method for the facile synthesis of organic-inorganic hybrid materials with a controllable mesostructure under mild synthetic conditions.
TL;DR: In this article, the effect of pH on the release pattern of tetracycline hydrochloride has been studied by varying the pH of the release medium, and it has been observed from the release dynamics of drug from the hydrogels that the diffusion exponent ‘ n ’ have 0.477, 0.423 and 0.427 values and gel characteristic constant ‘ k ’ has 5.34, 6.34 and 6.38, respectively, in distilled water, pH 2.2 buffer and pH 7.4 buffer solution.
TL;DR: The effect of adding surface-active agents to electrolytes containing terazosin, an antihypertensive drug, on the voltammetric response of glassy carbon electrode was studied and the validity of using this method in the determination of drug active ingredient in urine samples and tablet formulations was demonstrated.
TL;DR: In this paper, a mesoporous material with large pore size was synthesized from mixtures of sodium silicate (Na2SiO3) and tetraethoxysilane (TEOS) in acetic acid/sodium acetate buffer solution.
TL;DR: In this paper, the electrocatalytic ability of modified glassy carbon electrodes for the reduction of dioxygen to hydrogen peroxide was investigated by using cyclic voltammetry and chronocoulometry techniques at poly( p -aminobenzene sulfonic acid) (PABS)-modified glassy Carbon electrodes.
Abstract: The electrocatalytic ability of the modified electrodes for the reduction of dioxygen to hydrogen peroxide was investigated by using cyclic voltammetry and chronocoulometry techniques at poly( p -aminobenzene sulfonic acid) (PABS)-modified glassy carbon electrodes. The electrochemical reduction of oxygen (O 2 ) has been studied in pH 7.0 buffer solution by using PABS-modified glassy carbon rotating ring disk electrode (RRDE). The PABS-modified glassy carbon (GC) electrode (GC/PABS) showed excellent electrocatalytic activity for oxygen and hydrogen peroxide (H 2 O 2 ) reduction reactions. The RRDE data indicated that the reduction of oxygen on GC/PABS electrodes proceeds by a two-electron pathway in aqueous buffer solution (pH 7.0). In addition, PABS-coated GC electrode was successfully utilized as an enzyme-less amperometric sensor for the detection of hydrogen peroxide (H 2 O 2 ) in the range from 50 to 550 μM with detection limit of (S/N = 3) 10 μM.
TL;DR: The CeHCF/MWNT/GC electrode showed potent electrocatalytic activity toward the electrochemical oxidation of tryptophan in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of 240mV.
TL;DR: This sensor was stable, reproducible and outstanding for long-term use and shows excellent electrocatalytic effect towards the oxidation of both AA and UA, and separates the voltammetric signal of UA from AA by about 280 mV, allowing simultaneous detection of these two species.
TL;DR: In this paper, a functional membrane modified gold electrode was used as a biosensor and exhibited a satisfactory stability and sensitivity to H2O2, with a linear range of sensitivity from 5.0 to 1.5 mV.
TL;DR: In this paper, the authors measured the distribution coefficient of penicillin G between the buffer solution and ionic liquids, including hexafluorophosphates of 1-n-butyl-, 1n-hexyl- and 1n octyl-3-methyl imidazolium, and trioctylmethylammonium chloride (TOMAC).
TL;DR: A local equilibrium model is presented to predict the magnitude and duration of complex pH transitions in cation exchange columns used for protein chromatography during equilibration and salt elution steps and it is demonstrated that the magnitude of the pH transitions occurring during salt steps is nearly independent of the buffer system.
TL;DR: An adsorptive stripping voltammetric procedure for the determination of U(VI) at an in situ plated lead film electrode is described and was validated in the course of U (VI) determination in water certified reference materials.
TL;DR: In this article, a glassy carbon electrode covalently modified with penicillamine was used for the simultaneous determination of hydroquinone (HQ) and catechol (CC).
Abstract: A simple and highly selective electrochemical method has been developed for the simultaneous determination of hydroquinone (HQ) and catechol (CC) at a glassy carbon electrode covalently modified with penicillamine (Pen). The electrode is used for the simultaneous electrochemical determination of HQ and CC and shows an excellent electrocatalytical effect on the oxidation of HQ and CC upon cyclic voltammetry in acetate buffer solution of pH 5.0. In differential pulse voltammetric measurements, the modified electrode was able to separate the oxidation peak potentials of HQ and CC present in binary mixtures by about 103 mV although the bare electrode gave a single broad response. The determination limit of HQ in the presence of 0.1 mmol L−1 CC was 1.0 × 10−6 mol L−1, and the determination limit of CC in the presence of 0.1 mmol L−1 HQ was 6.0 × 10−7 mol L−1. The method was applied to the simultaneous determination of HQ and CC in a water sample. It is simple and highly selective.