Phosphate Buffer Solution Concentration Research Articles

Hydrogen-bonded organic frameworks as stationary phase for open-tubular capillary electrochromatography

BackgroundCapillary electrochromatography (CEC) stationary phases have always been the focus of attention. The selection of excellent stationary phases are the key to realize separate of different compounds. Hydrogen-bonded organic frameworks (HOFs) are porous materials connected by hydrogen bonds between molecules, which have the advantages of renewable, high specific surface area and mild synthesis conditions. At present, HOFs are used in gas adsorption and storage, catalysis and drug delivery. Because of its unique advantages, HOFs have a bright future as CEC stationary phases. ResultsUsing melamine (MA) and 1,3,6,8-tetra (4-carboxylphenyl)pyrene (H4TBAPy) as reaction monomers, a HOFs named MA/PFC-1 was synthesized by solvent evaporation at room temperature. The inner wall of the capillary column was coated with MA/PFC-1 by chemical bonding. Sulfonamides were used as the target analytes. The effects of pH, phosphate buffer solution concentration, organic additive content and applied voltage on sulfonamides separation were investigated. The MA/PFC-1-coated capillary column had good resolution (>1.5) and reproducibility. The intra-day, inter-day, column-to-column, and inter-batch precision of the retention times were 0.03%–0.09%, 0.04%–0.09%, 0.03%–0.14% and 0.06%–0.09%, respectively. The intra-day, inter-day, column-to-column, and inter-batch precision of the peak areas were 0.11%–0.25%, 0.13%–0.20%, 0.12%–0.15% and 0.08%–0.15%, respectively. The MA/PFC-1-coated capillary column was run 150 consecutive times, and the results showed no noticeable change, which proved that this method had good stability. SignificanceThis work applied HOFs to CEC. The results show the that MA/PFC-1-coated capillary column has good separation performance. The MA/PFC-1-coated capillary column has been successfully applied to the determination of sulfamethoxazole in tablets, which has practical application value. To open up the application of HOFs in CEC and provide a new idea for developing new CEC stationary phases.

Fabrication of Carbon Paste Sensor Activated with Electropolymerized DL‐Phenylalanine for the analysis of Levofloxacin

AbstractVoltammetric analysis of Levofloxacin (LF) using an electrochemically polymerized composite of DL‐phenylalanine (DLP) alongside a bare carbon paste electrode. The constructed electrodes are polymerized DL‐phenylalanine modified carbon paste electrodes P(DLP/MCPE) and bare carbon paste electrodes (BCPE). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and other electrochemical techniques used for characterization of P(DLP/MCPE) and BCPE in 0.2 M phosphate buffer solution (PBS) with pH 4.5 were conformed using the P(DLP/MCPE), and it shows the highest current responses compared to the BCPE. This research work examines the effect of pH in PBS, scan rate, and LF concentration on the surface of P(DLP/MCPE). The outcome result shows that the oxidation reaction of LF pH is an adsorption‐controlled path. The detection limit of LF ranges from 0.2 μM to 7.0 μM, and the lower limits of detection (LOD) is 0.613x10−7 M and the lower limits of quantification (LOQ) is 2.051X10−7 M. The electrochemical P(DLP/MCPE) shows good repeatability, reproducibility, and stability. Finally, by analyzing LF in a pharmacological sample, the real time application of the sensor was assessed, and significant recoveries were observed.

One-step fabrication of three-dimensional macropore copolymer-modified polycarbonate array by photo-crosslinking for protein immunoassay.

A photocross-linked copolymer was prepared, and could rapidly form a macropore structure in phosphate buffer solution (PBS) without the addition of porogen. The photo-crosslinking process contained the crosslinking of the copolymer itself and that with the polycarbonate substrate. The three-dimensional (3D) surface was achieved through one-step photo-crosslinking of the macropore structure. The macropore structure can be finely regulated by multiple dimensions, including monomer structure of the copolymer, PBS and copolymer concentration. Compared with the two-dimensional (2D) surface, the 3D surface has a controllable structure, a high loading capacity (59 μg cm-2) and immobilization efficiency (92%), and the effect of inhibiting the coffee ring for protein immobilization. Immunoassay results show that a 3D surface immobilized by IgG has high sensitivity (LOD value of 5 ng mL-1) and broader dynamic range (0.005-50 μg mL-1). This simple and structure-controllable method for preparing 3D surfaces modified by macropore polymer has great potential applications in the fields of biochips and biosensing.

Electrospun Polyacrylonitrile/Polythiophene Fibers for Phosphate Anion Sensing

Electrospun fibers are widely used in various applications such as tissue engineering, wound healing, drug delivery, materials science, chemical industry, energy storage, and sensor thanks to their combination of unique properties such as large surface area, high mechanical stability, high porosity, and great electrical conductivity. In addition, conducting polymers (CPs) used in fiber structures offer an extraordinary range of materials due to their diverse properties such as electrical and optical properties, the possibility of both chemical and electrochemical synthesis, and ease of processing.
 Among CPs, polythiophene (PTh) is highly important due to its unique redox electrical behavior, ease of synthesis, and application in many fields.
 In this study, 10 wt% polyacrylonitrile (PAN) fibers (P1), 10 wt% PAN/1 wt% PTh fibers (P2), and 10 wt% PAN/3 wt% PTh fibers (P3) were produced using an electrospinning technique. The structures, the morphologies and the electroactivities of the electrospun fibers were characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), Thermogravimetric analysis (TGA), and Cyclic voltammetry (CV). FTIR, SEM-EDX and TGA results supported the presence of PTh in PAN fibers.
 The electrochemical behaviors of indium-tin-oxide (ITO) glasses coated with the P1, P2, and P3 fibers in phosphate buffer solution (PBS) at various concentrations were assessed by CV. These electrospun fibers containing PTh were used for phosphate anion sensing. For all fiber samples, the oxidation potential increased with a decreasing concentration of phosphate buffer solution. The obtained results indicated that the thermal stability and electrical conductivity of the fibers were affected by PTh. This study shows that PAN fibers containing PTh as anionic sensors can be used as new recognition models.

Quantifying the factors limiting performance and rates in microbial fuel cells using the electrode potential slope analysis combined with electrical impedance spectroscopy

Improving power generation of microbial fuel cells (MFCs) requires better methods to quantify the impact of the solution chemistry on performance. While buffer concentration and conductivity have been indicated to impact performance of flat (carbon cloth) anodes, we were able for the first to time to quantitatively determine the impact of the phosphate buffer solution (PBS) concentration separate from conductivity on electrode resistances of commonly used brush anodes and activated carbon cathodes. Using the electrode potential slope (EPS) method, we showed that the anode resistance decreased by 64% (from 14.6 ± 0.1 mΩ m2 to 5.3 ± 0.1 mΩ m2) by increasing the PBS concentration from 50 to 200 mM. There was no appreciable change in the cathode resistance (17.0 ± 0.1 mΩ m2, 50 mM; 18.9 ± 0.2 mΩ m2, 200 mM) although overall performance increased due to a larger cathode experimental working potential (ECat,e0-50= 268.9 ± 0.9 mV, ECat,e0-200= 370 ± 1 mV). Adding phosphate buffer to low conductivity synthetic wastewater containing 0.25 g L−1 sodium acetate decreased the anode resistance by 52% (from 59.1 ± 0.2 mΩ m2 to 28.1 ± 0.1 mΩ m2), but increasing only conductivity by adding NaCl or acetate had little impact on electrode resistances. Using electrochemical impedance spectroscopy (EIS), we determined the reasons for these responses. The cathode was limited by oxygen reduction reaction (ORR) kinetics, while the brush anode was limited by mass transfer (proton diffusion), consistent with the impact of buffer concentration on performance. These results have important implications for operation of MFCs as increasing solution conductivity alone, for example, by adding seawater, will not be sufficient to improve anode performance.

Performance of microbial desalination cell for salt removal and energy generation using different catholyte solutions

Microbial desalination cell (MDC) is a bioelectrochemical process for simultaneous bioelectricity generation, wastewater treatment, and water desalination. The major drawback of MDC improvement is using toxic catholyte solutions which are normally employed in cathode chamber. In this study, the performance of microbial desalination cell using buffer saline solution was investigated for the first time. The obtained results were compared to several low-cost catholyte solutions, including low concentration of phosphate buffer solution (PBS), non-buffer saline solution, and bio-catholyte. All MDC reactors were fed with actual urban wastewater as fuel. Among all examined catholyte solutions, the MDC using bio-catholyte achieved the highest power density of 32.6Wm−3, followed by the MDC using saline buffer catholyte with maximum power density of 29.4Wm−3. Bio-catholyte had also lower internal resistance, and it improved current generation; maximum COD removal and desalination rate were 80% and 0.38g NaClL−1h−1, respectively. On the other hand, in the MDC with buffer saline solution, the COD removal and desalination rate were 73.1% and 0.34g NaClL−1h−1, respectively. In the MDCs using PBS and non-buffer saline solution, maximum power density was 11.1 and 16.3Wm−3, respectively. Based on experimental data, Among the examined catholytes, wastewater as bio-catholyte and saline buffer solution were the desired candidates for MDC scale up, and the most promising point was their being inexpensive alternatives to supplant the costly MDCs catholytes.

Mixed SDS-Hemin-Imidazole at low ionic strength being efficient peroxidase-like as a nanozyme

The presence of a simple surfactant, sodium n-dodecyl sulfate (SDS), at a particular concentration provided a suitable hydrophobic pocket for heme-imidazole moiety, which produced a peroxidase active site containing negative charges distributed on the colloidal surface. It is important that which aggregation structure of SDS encompasses the heme-imidazole as peroxidase active site. Ionic strength variation is an important key that can be used to obtain wide range of hydrophobic pocket in different structures. Here heme-imidazole complex was embedded into SDS micelles in different ionic strengths via phosphate buffer solution (PBS) variation and it has been investigated structurally and functionally. The critical micelle concentrations (CMC) of SDS were determined in different ionic strengths of PBS by using condutometry. The catalytic activity of triple-component: SDS-heme-imidazole, indicated that the catalytic efficiency of the novel “nanozyme” at PBS 0.2mM was 28.7% of native horseradish peroxidase (HRP) which is related to the formation of a unique and discrete nano-structure of peroxidase-like biocatalyst at low ionic strength which obtained by Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetery (DSC) experiments. The important role of hydration layer force in assembling the particular colloid structure that causes the suitable structural thermal profile in special low PBS concentration (0.2mM) determined by DSC method. The final biomimetic structure of micellar SDS-Heme-imidazole as an efficient artificial peroxidase as well as imidazole role on nanozyme stability was resolved by molecular dynamics simulation based on hydrodynamic radii measured by Dynamic Light Scattering (DLS).

Extraction of apine winter wheat antifreeze protein and detection of the antifreeze activity

Supposing alpine winter wheat as raw material,antifreeze protein extracted from alpine winter wheat by phosphate buffer solution and ice process.Though single factor and response surface test,we concluded that the best process conditions of alpine winter wheat antifreeze protein was: the material liquid ratio was 1 ∶ 15,concentration of phosphate buffer solution was 10 mol / m L,p H was 7.8,stirring time was 2 h,ice hockey was 10,ice time was 2 min,the ice temperature was-10 ℃.Under this condition the extraction yield of antifreeze protein from alpine winter wheat was 18.2%.After extraction of antifreeze protein from alpine winter wheat,producing into freeze drying,and redissolving into 5%,its ice crystals observed to detect the antifreeze activity of alpine winter wheat protein.According to the results,the ice crystals were in order forms,and have good antifreeze activity.Applying to the frozen dough,it could improve the quality of frozen dough.

Miniaturized and direct spectrophotometric multi-sample analysis of trace metals in natural waters

Trends in the analysis of trace metals in natural waters are mainly based on the development of sample treatment methods to isolate and pre-concentrate the metal from the matrix in a simpler extract for further instrumental analysis. However, direct analysis is often possible using more accessible techniques such as spectrophotometry. In this case a proper ligand is required to form a complex that absorbs radiation in the ultraviolet–visible (UV–Vis) spectrum. In this sense, the hydrazone derivative, di-2-pyridylketone benzoylhydrazone (dPKBH), forms complexes with copper (Cu) and vanadium (V) that absorb light at 370 and 395 nm, respectively. Although spectrophotometric methods are considered as time- and reagent-consuming, this work focused on its miniaturization by reducing the volume of sample as well as time and cost of analysis. In both methods, a micro-amount of sample is placed into a microplate reader with a capacity for 96 samples, which can be analyzed in times ranging from 5 to 10 min. The proposed methods have been optimized using a Box–Behnken design of experiments. For Cu determination, concentration of phosphate buffer solution at pH 8.33, masking agents (ammonium fluoride and sodium citrate), and dPKBH were optimized. For V analysis, sample (pH 4.5) was obtained using acetic acid/sodium acetate buffer, and masking agents were ammonium fluoride and 1,2-cyclohexanediaminetetraacetic acid. Under optimal conditions, both methods were applied to the analysis of certified reference materials TMDA-62 (lake water), LGC-6016 (estuarine water), and LGC-6019 (river water). In all cases, results proved the accuracy of the method.

Development of a square wave voltammetric method for dopamine determination using a biosensor based on multiwall carbon nanotubes paste and crude extract of Cucurbita pepo L.

The development of an enzymatic biosensor for dopamine (DA) determination based on functionalized multiwall carbon nanotubes (MWCNTs) and horseradish peroxidase (HRP) obtained from the crude extract of zucchini (Cucurbita pepo L.) is proposed. The biosensor was developed by means of the immobilization of the enzyme by covalent bonding to carrier MWCNTs functionalized. In the presence of hydrogen peroxide, HRP catalyzes the oxidation of DA to o-dopaquinone and the reduction of o-dopaquinone, which requires a low potential difference. The influence on the response of analytical parameters of biosensor such as enzyme concentration, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) concentration, H2O2 concentration, pH and phosphate buffer solution concentration, as well as the electroanalytical technique, cyclic voltammetry, square wave voltammetry and differential pulse voltammetry were investigated. The analytical parameters obtained including the sensitivity, linearity, precision, accuracy, and stability were investigated and were within the recommended guidelines. The validated method proved to be efficient for DA determination in pharmaceutical formulation and presented good selectivity even in the presence of uric acid and ascorbic acid.

THE EFFECT OF PROCESS VARIABLES ON THE PROPERTIES OF KETOPROFEN LOADED SOLID LIPID NANOPARTICLES OF BEESWAX AND CARNAUBA WAX

Solid Lipid Nanoparticles (SLNs) have emerged as an alternative colloidal carriers for sustained release of lipophilic drugs with poor absorption and water solubility. This manuscript describes the effect of process variables on the production of Solid Lipid Nanoparticles (SLNs) from beeswax and carnauba wax and ketoprofen release from these carriers. It was found that by increasing drug content from 0.5 to 1.5% w/v the average particle size of SLNs increased from 82 to 116 nm and drug loading increased from 10.7 to 26.6% while entrapment efficiency remained almost constant (≈ 97%). Unexpectedly, the average size of SLNs increased from 82 to 150 nm by increasing homogenization time from 5 to 15 min. Increasing homogenization intensity from 11000 to 24000 rpm resulted in the particle size decrease from 108 to 82 nm. The rate of drug release from nanparticles loaded with 0.5% w/v ketoprofen increased with increasing the ionic concentration of phosphate buffer solution from 0.05 to 0.1 M.

Gold nanoparticles-coated eggshell membrane with immobilized glucose oxidase for fabrication of glucose biosensor

This work reports the fabrication and application of a glucose biosensor based on the catalytic effect of gold nanoparticles (AuNPs) on enzymatic reaction for blood glucose determination. AuNPs were initially in situ synthesized on the surface of an eggshell membrane (ESM) which was subsequently immobilized with glucose oxidase (GO x) to produce a GO x-AuNPs/ESM. The GO x-AuNPs/ESM was positioned on the surface of an oxygen electrode to form a GO x-AuNPs/ESM glucose biosensor. The effects of pH, concentration of phosphate buffer solution and amount of GO x on the response of the GO x-AuNPs/ESM glucose biosensor were studied in detail. AuNPs on GO x/ESM can improve the calibration sensitivity (30% higher than GO x/ESM without AuNPs), stability (87.3% of its initial response to glucose after 10-week storage) and shortens the response time (<30 s) of the glucose biosensor. The linear working range for the GO x-AuNPs/ESM glucose biosensor is 8.33 μM to 0.966 mM glucose with a detection limit of 3.50 μM ( S/ N = 3). The biosensor has been successfully applied to determine the glucose in human blood serum samples and the results compared well to a standard spectrophotometric method commonly used in hospitals. Our work demonstrates that the developed GO x-AuNPs/ESM glucose biosensor has potential in biomedical analysis.

Immobilized multi-species based biosensor for rapid biochemical oxygen demand measurement

To improve the practicability of rapid biochemical oxygen demand (BOD) method, we proposed a stable BOD sensor based on immobilizing multi-species BODseed for wastewater monitoring in the flow system. The activation time of the biofilm was greatly shortened for the biofilm prepared by BODseed in the organic–inorganic hybrid material. Some influence factors such as temperature, pH, and concentration of phosphate buffer solution (PBS) were investigated in detail in which high tolerance to environment was validated for the BOD sensor permitted a wide pH and PBS concentration ranges. The minimum detectable BOD was around 0.5 mg/l BOD under the optimized 1.0 mg/ml BODseed immobilized concentration. The as-prepared BOD sensor exhibited excellent stability and reproducibility for different samples. Furthermore, the as-prepared BOD biosensor displayed a notable advantage in indiscriminate biodegradation to different organic compounds and their mixture, similar to the character of conventional BOD 5 results. The results of the BOD sensor method are well agreed with those obtained from conventional BOD 5 method for wastewater samples. The proposed rapid BOD sensor method should be promising in practical application of wastewater monitoring.

Electroosmotic flow in poly(dimethylsiloxane) microchannels

This paper reports on the study of electroosmotic flow (EOF) in poly(dimethylsiloxane) (PDMS) microchannels on the basis of indirect amperometric detection method. Gradual increase of EOF rate in freshly prepared PDMS microchannels was observed with the running buffer of phosphate buffer solution (PBS). With the same concentration (10 mM) of PBS containing different cations and the same pH value (7.0) and, the time of the stable EOF in PDMS microchannels under the applied separation voltage of 1000 V was 49.8 s (Li +-PBS), 57.1 s (Na +-PBS), 91 s (K +-PBS), respectively. Meanwhile, the different adsorption of cations (Li +, Na + and K +) on hydrophobic PDMS wall was observed through their separation in PDMS microchannels. Such experimental results demonstrated that the EOF in PDMS microchannels came from the cations and anions adsorbed on PDMS wall. This study would not only help us understand the surface state of PDMS, but also provide a useful guidance for establishing the effective surface modification methods in PDMS microchip CE.

Adsorption/desorption of acidic and basic proteins on needle-like hydroxyapatite filter prepared by slip casting

The adsorption/desorption of proteins, such as the bovine serum albumin (BSA) as an acidic protein and the lysozyme chloride (LYZ) as a basic protein, was investigated with the needle-like hydroxyapatite(N-HAp) filters after fired at several fixed temperatures. The filters were prepared by a slip casting with the aqueous N-HAp(commercial powder:Ca/P=1.54) slips supplemented with calcium hydroxide [Ca(OH) 2] for the lack of calcium. The cast filters were fired in H 2O vapor at the range of 600–1200 °C. The adsorbed amounts were measured with the N-HAp fired filters. For both the BSA and LYZ, the adsorbed amounts increased with increasing the fired temperatures. Furthermore, the proteins desorption was also investigated by a column chromatograph using the linear gradient method with the sodium phosphate buffer solution (PBS). The PBS concentration at which the BSA was desorbed from the filters was independent to the firing temperature of the filters. However, for the LYZ, the PBS concentration increased with increasing the fired temperatures. From the results, it was found on the filters fired more than 1000 °C that the LYZ adsorbed stronger to the HAp filters than the BSA.

NANO-GOLD MODIFIED GLASSY CARBON ELECTRODE FOR SELECTIVE DETERMINATION OF EPINEPHRINE IN THE PRESENCE OF ASCORBIC ACID

ABSTRACT The nano-gold modified glassy carbon electrode, which can catalytically oxidize and accumulate epinephrine was obtained by electrodeposition. The effect of pH value and concentration of phosphate buffer solution (PBS) on the electrochemical behavior of epinephrine was studied. Two separating oxidation peaks of epinephrine and ascorbic acid can be observed at the nano-gold modified glassy carbon electrode in cyclic voltammogram. So it can be applied for determination of epinephrine in the presence of ascorbic acid. The peak current of epinephrine is in linear relationship with its concentration in the range of 1.0 × 10−4–1.0 × 10−6 M. Furthermore, the FT-IR spectrometry was employed to study the oxidation of epinephrine.

原生動物縁毛類の増殖に及ぼす環境因子の影響

Small aquatic Peritrichida are the typical protozoa found frequently in the activated sludge and bio-film from wastewater treatment system. Effect of environmental factors on growth characteristics of aquatic Peritrichida, Vorticella microstoma and Vorticella convallaria were investigated. Using a sterilized activated sludge as the protozoan food, the effects of temperature, pH, phosphate buffer solution concentration, shake stress and food concentration on the monoxenic growth rate of small Peritrichida were measured. Optimum temperature of V. microstoma and V. convallaria were 25°C. Phosphate buffer concentrations which could grow normally were 1/75M for each Peritrichida. The optimum pH values ranged from 5.7 to 7.7 for V. microstoma and ranged from 4.7 to 8.7 for V. convallaria. The endurance against shake stress was lower than those of Rotatoria and Oligochaeta.

袋形動物輪虫類の増殖に及ぼす環境因子の影響

Small aquatic rotatoria are the typical micrometazoa found frequently in the activated sludge and bio-film from wastewater treatment system. Effect of environmental factors on growth characteristics of aquatic rotatoria, Philodina erythrophthalma, Rotaria rotatoria, Lecane luna were investigated. Using a sterilized activated sludge as the micrometazoa food, the monoxenic growth rate of small rotatoria, the effects of temperature, pH, phosphate buffer solution concentration, shake stress, food concentration were measured. Optimum temperature of P. erythrophthalma, R. rotatoria, L. luna were 30, 30, 25°C, respectively. Phosphate buffer concentration which could grow normally were 1/25 M for all rotatoria. The optimum pH valuesin cultivating the rotatoria ranged from 5 to 9. The endurance of P. erythrophthalma and R. rotatoria against shake stress was higher than that of L. luna.

環形動物貧毛類の増殖に及ぼす環境因子の影響

Small aquatic Oligochaetes are the typical metazoa found frequently in the activated sludge and bio-film from wastewater treatment system. Effect of environmental factors on growth characteristics of aquatic Oligochaetes, Aeolosoma hemprichi, Pristina longiseta, Nais variabilis were investigated. Using a sterilized activated sludge as the metazoan food, the monoxenic growth rate of small aquatic Oligochaetes, the effects of temperature, pH, phosphate buffer solution concentration, shake stress, food concentration were measured. Optimum temperature of A.heyprichi, P.longiseta, N.variabilis were 30, 35, 35°C, respectively. Phosphate buffer concentration which could grow normally were 1/375M for A. hemprichi, 1/150M for P. longiseta and N.variabilis. The optimum pH values in cultivating the Oligochaetes ranged from 5 to 9. The endurance of A. hemprichi against shake stress was higher than that of P. longiseta and N.variabilis.