Potassium Ferricyanide Solution Research Articles

Simultaneous determination of six rare sugars in solid foods by high performance liquid chromatography-evaporative light-scattering detection

Excessive sugar consumption is associated with metabolic health problems. Rare sugars are gradually being used as substitutes for sugar, and their consumption is increasing daily, raising food-safety issues such as false advertising, adulteration, and overdosing. The determination of rare-sugar compounds has attracted considerable attention in recent years. However, no standard method for the simultaneous determination of six rare sugars (allulose, tagatose, trehalose, isomaltulose, erythritol, and mannitol) in solid foods is available. Therefore, establishing a suitable analytical method for these sugars is necessary. In this study, high performance liquid chromatography coupled with evaporative light-scattering detection was used to determine rare sugars in solid foods. The optimum chromatographic and detector conditions were determined by evaluating the instrument parameters. Analysis was carried out on a Zorbax Original NH2 column (250 mm×4.6 mm, 5 μm) via flow-rate gradient elution (0-15 min, 1.0 mL/min; 15-18 min, 1.0-2.0 mL/min; 18-25 min, 2.0 mL/min) with acetonitrile-water (80∶20, v/v) as the mobile phase. Sharp and symmetric chromatographic peaks were obtained under these conditions. The resolutions for all the six rare sugars were greater than 1.5. Optimization of the evaporative light-scattering detector was extremely important to the responses of the rare-sugar compounds. The two most significant parameters were the nebulizer carrier gas flow rate and drift tube temperature. The detection system was operated under the following conditions: the drift tube temperature was set to 50 ℃, the nebulizer carrier gas was high-purity nitrogen, the carrier gas flow rate was 1.0 mL/min, the nitrogen pressure was regulated to 275.79 kPa, and the gain factor was set to 3. The sample was extracted with 25 mL of water, shaken and vortexed for 10 min, purified with 200 μL of zinc acetate solution and 200 μL of potassium ferricyanide solution, and centrifuged at 4500 r/min for 10 min. Next, 1 mL of the supernatant was passed through a 0.22 μm aqueous-phase filter membrane, and the filtrate obtained was analyzed using the evaporative light-scattering detector. The six rare sugars were quantitatively analyzed using the external standard method and showed good linearity with coefficients of determination (R2) greater than 0.9985. The limits of detection and quantification were 0.020-0.60 and 0.60-1.8 g/100 g, respectively. In addition, when blank solid food samples were spiked with the analytes at three levels, the average recoveries of the six rare sugars were 92.6%-103.2%, with relative standard deviations (RSDs) of 0.7%-4.4%. An RSD of <5% indicated that the method had good precision. Interference experiments were performed to determine whether the sugars and artificial sweeteners commonly found in solid foods affected the targets. The method established in this study was used to analyze the contents of the six rare sugars in actual solid food samples. The experimental results showed various levels of rare glycoconjugates in different solid foods. Moreover, the actual compositions and labeled of rare glycoconjugates in the solid foods were generally consistent. The proposed method features simple operation, rapid results, high sensitivity, and good reproducibility; thus, it meets the requirements for the detection of the six rare sugars in solid foods. It also provides technical support for the development of methodological standards and detection limits for rare sugars in Chinese foods. The results of this study are of great relevance for the daily monitoring of the levels of the six rare sugars in solid foods.

Anthropogenic greenhouse CO2 gas sensor based on glassy carbon modified with organoclay/ polypyrrole-alginate nanocomposites in brackish water and seawater

Schematic presentation of the detection of CO 2 using a glassy carbon sensor (GCS) and modified glassy carbon sensor (MGCS) based on organoclay/polypyrrole-alginate (OC/Ppy-A) nanocomposite via cyclic voltammetry. • An anthropogenic greenhouse CO 2 gas sensor was successfully fabricated. • The sensor exhibited remarkable conductivity and electrocatalytic activity. • Low detection limits and a wide linearity range were observed. • The sensor was successfully applied to detect CO 2 in brackish and seawater samples. An increase in the amount of greenhouse gases around the Earth’s atmosphere generated by emissions through various sources creates a huge problem for the near future because of global warming and the consequent climate changes. This study fabricated an organoclay/polypyrrole-alginate (OC/Ppy-A) nanocomposite-modified glassy carbon sensor (MGCS), which was used for the sensitive estimation of anthropogenic greenhouse gas (CO 2 ). The efficiency of the developed sensor was investigated via cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Compared with the bare glassy carbon sensor (GCS), the developed MGCS exhibited a fivefold superior CV signal for the recognition of the redox-active solution of potassium ferricyanide (K 3 [Fe(CN) 6 ]). The CV signal currents of the redox reaction of (K 3 [Fe(CN) 6 ]) were changed by changing the amount of CO 2 molecules in the measured samples. The oxidation signal of (K 3 [Fe(CN) 6 ]) linearly correlated with the CO 2 concentration in the separate ranges of 0.05–0.25 ppm (0.595–2.98 µM) and 0.25–3.5 ppm (2.98–41.67 µM) with limits of detection (S/N = 3) of 0.0165 ppm (0.196 µM, 40.569 μA/ppm) and 0.0825 ppm (0.982 µM, 1.751 μA/ppm). Additionally, the developed electrochemical MGCS exhibited appropriate repeatability, reproducibility, and stability. The proposed sensor was successfully applied for the determination of CO 2 in brackish and seawater samples in Egypt.

INTRODUCING HYDROCOLLOID WOUND DRESSING ENERGY DISRUPTING HUMAN TISSUE METABOLISM

The development in 2016 of a novel Potassium Ferricyanide of formula (K₃[Fe(CN)₆]) based tabletop microscopy method enabled for the recording of electromagnetic energy emissions from plants and animal tissue. The microscopy method was subsequently validated and used to document inter-tissue energy exchanges of both, human blood, and catalase proper with a hair follicle. As of recent in vitro research using hair follicles as sentinels support expanding an endogenous irradiation theory as disease causing mechanism introduced in 1956 and revisited in 2016 to now also include non-biological exogenous irradiation emitted by hydrocolloid based wound dressings (WD). Videos and still images are presented validating the findings of energy emitted by a small fragment of a hydrocolloid based WD penetrating a 1mm glass slide and unexpectedly delaying the evaporation time of a Potassium Ferricyanide solution surrounding a freshly plucked human hair follicle. Absorption of Incoming electromagnetic radiation is a property of (K₃[Fe(CN)₆]). The introduction of energy from an exogenous non-biological material, namely a hydrocolloid wound dressing fragment justifies inclusion in future research protocols.

Fabrication of High-Density Vertical Closed Bipolar Electrode Arrays by Carbon Paste Filling Method for Two-Dimensional Chemical Imaging.

In this study, a carbon paste filling method was proposed as a simple strategy for fabricating high-density bipolar electrode (BPE) arrays for bipolar electrochemical microscopy (BEM). High spatiotemporal resolution imaging was achieved using the fabricated BPE array. BEM, which is an emerging microscopic system in recent years, achieves label-free and high spatiotemporal resolution imaging of molecular distributions using high-density BPE arrays and electrochemiluminescence (ECL) signals. We devised a simple method to fabricate a BPE array by filling a porous plate with carbon paste and succeeded in fabricating a high-density BPE array (15 μm pitch). After a detailed observation of the surface of the BPE array using a scanning electron microscope, the basic electrochemical and ECL emission characteristics were evaluated using potassium ferricyanide solution as a sample solution. Moreover, inflow imaging of the sample molecules was conducted to evaluate the imaging ability of the prepared BPE array. In addition, Prussian Blue containing carbon ink was applied to the sample solution side of the BPE array to provide catalytic activity to hydrogen peroxide, and the quantification and inflow imaging of hydrogen peroxide by ECL signals was achieved. This simple fabrication method of the BPE array can accelerate the research and development of BEM. Furthermore, hydrogen peroxide imaging by BEM is an important milestone for achieving bioimaging with high spatiotemporal resolution such as biomolecule imaging using enzymes.

Influence of KNO3 on Capacitive Properties of Active Carbon in Potassium Ferricyanide Solutions

Influence of KNO3 on Capacitive Properties of Active Carbon in Potassium Ferricyanide Solutions

Electrochemical Detection of Dopamine at Fe3O4/SPEEK Modified Electrode.

Reported here is the design of an electrochemical sensor for dopamine (DA) based on a screen print carbon electrode modified with a sulphonated polyether ether ketone-iron (III) oxide composite (SPCE-Fe3O4/SPEEK). L. serica leaf extract was used in the synthesis of iron (III) oxide nanoparticles (Fe3O4NPs). Successful synthesis of Fe3O4NP was confirmed through characterization using Fourier transform infrared (FTIR), ultraviolet–visible light (UV–VIS), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). Cyclic voltammetry (CV) was used to investigate the electrochemical behaviour of Fe3O4/SPEEK in 0.1 M of phosphate buffer solution (PBS) containing 5 mM of potassium ferricyanide (III) solution (K3[Fe(CN)6]). An increase in peak current was observed at the nanocomposite modified electrode SPCE-Fe3O4/SPEEK) but not SPCE and SPCE-Fe3O4, which could be ascribed to the presence of SPEEK. CV and square wave voltammetry (SWV) were employed in the electroxidation of dopamine (0.1 mM DA). The detection limit (LoD) of 7.1 μM and 0.005 μA/μM sensitivity was obtained for DA at the SPCE-Fe3O4/SPEEK electrode with concentrations ranging from 5–50 μM. LOD competes well with other electrodes reported in the literature. The developed sensor demonstrated good practical applicability for DA in a DA injection with good resultant recovery percentages and RSDs values.

Comparative studies on vitamin B1 deficiency in whole blood of chronically haemodialysed patients: chromatographic, fluorimetric and PCA study

The levels of thiamine diphosphate (ThDP), the most active biologically form of vitamin B1, were assessed in whole blood oflong-term haemodialysed patients (n = 50), by applying chromatographic methods based on RP-HPLC technique with isocratic elution and fluorescence detection. The target analyte, thiochrome diphosphate (ThODP), was obtained by pre-column derivatization of vitamin B1 contained in blood samples, applying deproteination with trichloroacetic acid, following by oxidation with alkaline solution of potassium ferricyanide(III) and stabilization with DTT before assays. A simple and sensitive assay was developed, and the results were referenced to the commercially available test. Steady-state and time-resolved studies on emissive properties of ThODP enabled optimization of the proposed assay. The F-Snedecor test shown no statistically significant differences between both approaches. Assessed parameters of the proposed assay, such as linearity, precision, sensitivity, and recovery, were satisfactory if compared to the reference one. The LOQ value for ThDP in whole blood of studied group of patients was of 0.5 ng/mL and the recovery of88%. The results disclosed high individual variabilities in the interdialytic deficiencies of ThDP among the patients − ranged from afew percent to values close to 100%. A comprehensive clinical data, characterizing patients under study, were processed together, and analysed by employing achemometric discriminative tool, the Principal Components Analysis,to find interdependences among clinical data characterizing patients. The three Principal Components were disclosed, that in sum explained almost 50% of the observed variability of the clinical data set. Among the clinical parameters involved in PCs were dialyzer membrane and type, duration as well as levels of creatinine, haemoglobin, and red blood cells in patients’ whole blood.

Generation of Electricity from Pool Wastewater Using Bio-Mass Based Activated Charcoal Electrodes Through Microbial Fuel Cell

Conventionally, we use platinum/palladium as electrodes and Nafion as separator in the microbial fuel cells (MFCs), which are expensive and hazardous in nature. In this research, we employed bio-waste derived activated charcoal electrodes and eco-friendly lab glove separator for assessing the performance of laboratory-scale MFCs. The Activated Charcoals (AC) were synthesized from Palm fibers (Borassus flabellifer), Gooseberry seeds (Ribes grossularia) and Indian-almond (Terminalia catappa) seeds at high-temperature carbonization followed by ZnCl2 activation. The ACs was characterized in terms of pH and ash content. The porous structure and pore size distribution of the carbonized products and ACs were analyzed by Field Emission Scanning Electron Microscopy, and identified that the ACs possesses more porous structure than their carbonized precursors. We employed pool sludge (inoculums) as anodic solution and potassium permanganate solution as cathodic solution instead of using hazardous potassium ferricyanide solution. Here, we attained the highest voltage output of 0.92 V for the palm fiber-AC electrode based MFC. In this research, we employed cost effective and eco-friendly bio-waste based electrodes, eco-friendly separator, non-hazardous cathodic solution and nutrient-rich inoculums, thus the proposed scheme could be used for fabricating low cost, non-polluting and high performance MFCs.

(Keynote) Electrochemical Interface Using a New Double Mediator System for Intracellular NADH Sensing and Acute Cytotoxicity Test

Introduction Nicotinamide Adenine Dinucleotide (reduced form), NADH is a very important redox compound that is essential for metabolic reactions and ATP production in all living cells. Intracellular NADH metabolism is also important to consider the cancer treatment. Intracellular NADH has been conventionally measured by WST assay using a cell membrane-permeable redox mediator, 1-methoxy PMS (1-Methoxy-5-methylphenazinium methylsulfate) and a water soluble tetrazolium to form formazan. This colorimetric method is very easy and useful for cell counting and cytotoxicity test. However, WST assay is time-consuming and then it is not able to apply for evaluation of acute cytotoxicity by chemical compounds including drugs and pollutants. On the other hand, some research groups have already shown that electrochemical method with double mediator system is useful to monitor rapidly intracellular NADH level corresponding to the cell viability [1-5].In this paper, we would like to report the usefulness of the electrochemical interface using a small screen printed carbon electrode (SPCE) and a new double mediator system combining 1-methoxy PMS and ferricyanide. It was demonstrated that our electrochemical interface was available for faster and wide range of mammalian cell counting as compared with WST assay. Furthermore our method could be applied to acute cytotoxicity test on mammalian cells. The optimization of measurement condition is mentioned in the presentation and the advantages of our new double mediator system against other double mediator system are also discussed in the presentation. Experimental method We used PC12 cell (Rat adrenal pheochromocytoma cell line) as a mammalian cell sample. For the cell counting, the medium was exchanged to HBSS before experiments. After measurement of cell density of the original cell suspension with a hemocytometer, cell suspension was exactly diluted to prepare various density of cell suspension. Each diluted cell suspension was taken in a well of 96 well plate and final concentration of 500 μM potassium ferricyanide and 10 μM 1-metoxy PMS solution were added in a drop wise to the cell suspension. After incubation for 10 minutes, a SPCE (working electrode area is 1 mm2) was immersed into the cell suspension and chronoamperometric measurement was immediately performed by potential application at +0.5V vs. Ag/AgCl reference electrode on the SPCE.We further tried to test the acute cytotoxicity of oxamic acid that is a famous inhibitor of anaerobic glycolysis. Each concentration of oxamic acid/HBSS was prepared and added into PC12 cell/HBSS suspension (6 x 105 cells /well) in a well (final concentration of oxamic acid: 0 to 20 mM) and the cell suspension was incubated for 1hour. And then potassium ferricyanide (final 500 mM) and 1-metoxy PMS (final 10 μM) solutions were added into the cell suspension. After incubation for more 10 minutes, a SPCE was immersed into the cell suspension and chronoamperometric measurement was immediately performed by potential application at +0.5V. Results and c onclusions In the first stage it was demonstrated that our electrochemical interface with a new combination of double mediator system was very useful for very wide range of cell counting. The amperometric oxidation current showed very good linearity vs. the number of viable cells in the range from 7500 to 96400 cells/well (Data is not shown). The result strongly supported the combination of 1-methoxy PMS and ferricyanide is effective to monitor intracellular NADH level and to speculate the cell viability.Therefore, in the second stage, we applied our electrochemical interface to test the acute toxicity by oxamic acid. Figure 1 shows the decrease of oxidation current of the double mediator system after 1 hour oxamic acid treatment. The decrease of oxidation current was clearly dependent on the concentration of oxamic acid as shown in Figure 2. It indicated that intracellular NADH level corresponding to the cell viability was rapidly decreased by oxamic acid treatment. This result suggested that our electrochemical interface with a new double mediator system might be useful to evaluate acute cytotoxicity of drugs.

C-MEMS Derived Glassy Carbon Electrodes-Based Sensitive Electrochemical Biosensors

In this work, we have prepared glassy carbon electrodes using conventional carbon-microelectromechanical (C-MEMS) process. SU-8 photoresist has been used as the carbon precursor. The carbon thin film electrodes have then been tested by cyclic voltammetry measurements in the potential range of −800 mV to 800 mV vs Ag/AgCl electrode in presence of 10 mM potassium ferricyanide solution, without any functionalization. The samples have also been immobilized with anti-Hepatitis-B surface antigen (HBsAg) monoclonal antibody by physical adsorption. The presence of antibodies has been further confirmed by UV-VIS spectrophotometry. It has been observed that the current peak reduces distinctly and the fractional change in current magnitude is around 33% and 75% at the potential of 175 mV vs Ag/AgCl electrode for 10 fM and 100 fM concentration respectively. Hence, the presented study is the proof-of concept of electrochemical sensing behavior of HBsAg using functionalized glassy carbon electrodes which when integrated with low cost microfluidic platform can be suitable for point-of-care diagnostics.

Fabrication of Photocurable Hyaluronic Acid Coated Microneedle Sensor for Glucose Monitoring

Introduction Microneedle (MN) has been developed to diagnose and detect the biomarkers which are related to various diseases such as diabetes mellitus (DB) and caner. The biomarkers could be extracted from interstitial fluid (ISF) in the human body by using MN with a minimally-invasive and pain-free manner. In particular, glucose sensing has widely been investigated due to increase of DB patients who suffered inconvenience of frequent monitoring of glucose levels. MN-based sensors targeting ISF glucose monitoring was introduced and showed the possibility to replace the existing blood-based glucose sensing technologies [1-3]. We hypothesized that the coating of a MN surface with swellable material such as hydrogel could increase detection sensitivity and time for stabilization. Thus, we developed a swellable hydrogel coated MN sensor which could extract the glucose from ISF with swelling for a short time. Methacrylated hyaluronic acid (MeHA), photo-crosslinkable hydrogel, was utilized to absorb ISF containing biomarkers for electrochemical reaction with the metallized surface of a MN. Cyclic voltammetry (CV) with a model redox species, ferricyanide, were performed to characterize the MeHA-coated MN sensors for the detection of glucose. Experimental Methods To fabricate the MeHA coated MN sensor, 3×3 SU-8 MN array was transfer molded on the 1 cm × 2 cm of the glass wafer. The female PDMS mold which was patterned MN shapes were filled with SU-8 in a vacuum condition and the mold was gently transferred on the glass wafer. After UV curing, the MN electrode was prepared by the Ti-gold sputtering. MeHA was synthesized by modifying from the hydroxyl groups to the methyl group in basic condition. Dimethylformamide, methacrylic anhydride, and sodium chloride were mixed in the 2% of hyaluronic acid solution while a solution was controlled in basic condition. The precursor was washed three times by ethanol and was freeze-dried to obtain the MeHA sponges. Then, the MeHA sponges were dissolved into the deionized water which was contained 0.05% of the photoinitiator for preparing the MeHA solution. The MeHA solution was poured on the surface of gold-sputtered SU-8 MN arrays and the swellable MN sensor was fabricated after drying. Before measuring the glucose, potassium ferricyanide (K3[Fe(CN)6]) which was the standard redox solution to conduct CV was used as an alternative of the biomarker. The MeHA coated MN electrode was used as a working electrode and a Pt mesh electrode was used as a counter electrode. The MN sensor was immersed into the potassium ferricyanide solution and the CV was conducted while the concentration chose 10 mM, 10 μM, and 1 μM to confirm sensitivity and detection limit of the three-electrode system with MeHA coated MN sensor. Results and Discussion The 3×3 array of SU-8 MNs fabricated on a glass wafer had the height of 640 μm and the aspect ratio of 1.6. The MeHA was successfully synthesized and the MeHA film had a swelling ratio of 450% after 10 sec swelling in the phosphate buffered saline. By using the three-electrode system including the MeHA uniform coated MN electrode, in vitro sensing tests were performed with various concentrations of potassium ferricyanide. As the results of the CV analysis, when the concentration of potassium ferricyanide was 10 mM, the anodic and cathodic peak currents of the measured I-V curve were 135 and 144 μA, respectively. Although the peaks were observed from the CV plots, it was hard to measure the exact value of peak currents when the concentration of potassium ferricyanide, 10 μM, and 1 μM. Nevertheless, the current peaks of 10 μM was slightly higher than the peaks of the 1 μM sample. Since the peak current was increased in proportion to the level of potassium ferricyanide, it was concluded that the MeHA coated MN sensor system could be used to measure the biomarker. These results also support that the biomarkers could be extracted from the ISF by the swelling behavior of the MeHA coated on the surface of MNs. Summary The MeHA coated MN sensor was fabricated with simple molding techniques and various photocurable materials such as SU-8 2010 and MeHA. The ferricyanide could be extracted by using the swelling behavior of the MeHA. As the results of in vitro test, the various concentration of potassium ferricyanide solution was measured with the three-electrode system including MeHA coated MN sensor and the detection limit was observed at least 1 μM. Reference 1. Sharma, Sanjiv, et al. "A pilot study in humans of microneedle sensor arrays for continuous glucose monitoring." (2018).2. Caliò, A., et al. "Polymeric microneedles based enzymatic electrodes for electrochemical biosensing of glucose and lactic acid." Sensors and Actuators B: Chemical 236 (2016): 343-349.3. Ribet, Federico, Göran Stemme, and Niclas Roxhed. "Real-time intradermal continuous glucose monitoring using a minimally invasive microneedle-based system." Biomedical microdevices 20.4 (2018): 101.

Electrochemical Interface Using a New Double Mediator System for Intracellular NADH Sensing and Acute Cytotoxicity Test

Introduction Nicotinamide Adenine Dinucleotide (reduced form), NADH is a very important redox compound that is essential for metabolic reactions and ATP production in all living cells. Intracellular NADH metabolism is also important to consider the cancer treatment. Intracellular NADH has been conventionally measured by WST assay using a cell membrane-permeable redox mediator, 1-methoxy PMS (1-Methoxy-5-methylphenazinium methylsulfate) and a water soluble tetrazolium to form formazan. This colorimetric method is very easy and useful for cell counting and cytotoxicity test. However, WST assay is time-consuming and then it is not able to apply for evaluation of acute cytotoxicity by chemical compounds including drugs and pollutants. On the other hand, some research groups have already shown that electrochemical method with double mediator system is useful to monitor rapidly intracellular NADH level corresponding to the cell viability [1-5].In this paper, we would like to report the usefulness of the electrochemical interface using a small screen printed carbon electrode (SPCE) and a new double mediator system combining 1-methoxy PMS and ferricyanide. It was demonstrated that our electrochemical interface was available for faster and wide range of mammalian cell counting as compared with WST assay. Furthermore our method could be applied to acute cytotoxicity test on mammalian cells. The optimization of measurement condition is mentioned in the presentation and the advantages of our new double mediator system against other double mediator system are also discussed in the presentation. Method We used PC12 cell (Rat adrenal pheochromocytoma cell line) as a mammalian cell sample. The cells were grown in culture flasks containing DMEM with 5% FBS and 10%HS at 37℃ with 5% CO2 atmosphere. For the cell counting experiment, the medium was exchanged to HBSS before experiments. Cells were removed from the bottom of culture flask by trypsin treatment and suspended in HBSS. After measurement of cell density of the original cell suspension with a hemocytometer, cell suspension was exactly diluted to prepare various density of cell suspension. Each diluted cell suspension was taken in a well of 96 well plate and final concentration of 500 μM potassium ferricyanide and 10 μM 1-metoxy PMS solution were added in a drop wise to the cell suspension. After incubation for 10 minutes, a SPCE (working electrode area is 1 mm2) was immersed into the cell suspension and chronoamperometric measurement was immediately performed by potential application at +0.5V vs. Ag/AgCl reference electrode on the SPCE. The electrochemical measurement was carried out using a potentiostat (Multi-Autolab Cabinet, Metrohm Autolab).We further tried to test the acute cytotoxicity of oxamic acid that is a famous inhibitor of anaerobic glycolysis. Acute cytotoxicity test was carried out with the same electrochemical instrument by following procedure. Each concentration of oxamic acid/HBSS was prepared and added into PC12 cell/HBSS suspension (5.5 x 105 cells /well) in a well (final concentration of oxamic acid: 0 to 20 mM) and the cell suspension was incubated for 1hour. And then potassium ferricyanide (final 500 mM) and 1-metoxy PMS (final 10 μM) solutions were added into the cell suspension. After incubation for more 10 minutes, a SPCE was immersed into the cell suspension and chronoamperometric measurement was immediately performed by potential application at +0.5V. Results and Conclusions In the first place, it was demonstrated that our electrochemical interface with a new combination of double mediator system was very useful for very wide range of cell counting. The amperometric oxidation current showed very good linearity vs. the number of viable cells in the range from 7500 to 964000 cells/well (Data is not shown). The result strongly supported the combination of 1-methoxy PMS and ferricyanide is effective to monitor intracellular NADH level and to speculate the cell viability.Therefore, in the second place, we applied our electrochemical interface to test the acute toxicity by oxamic acid. The inset of Figure 1 shows the decrease of oxidation current of the double mediator system after 1 hour oxamic acid treatment. The decrease of oxidation current was clearly dependent on the concentration of oxamic acid. It indicated that intracellular NADH level corresponding to the cell viability was rapidly decreased by oxamic acid treatment. This result suggested that our electrochemical interface with a new double mediator system might be useful to evaluate acute cytotoxicity of drugs.

Colorimetric Determination of Uric Acid in Live samples

A simple, sensitive and precise colorimetric method for uric acid determination was described. The method based on the complexion reaction between uric acid, potassium ferricyanide, and ferric chloride in hydrochloric acid medium to form blue colored charge transfer complex measured at maximum wavelength 752 nm. The optimum conditions obtained were volume 0.3 ml for hydrochloric acid, 1.25 ml for both potassium ferricyanide and ferric chloride solutions, 60?C and 8 minutes as maximum temperature and time of reaction, the order of mixing additives was uric acid, ferric chloride, potassium ferricyanide, and hydrochloric acid. The highly accurate and precise results obtained with RSD%, Recovery%, Ere%, and D.L were (0.755 to 4.376), (99.676 to 97.831), (-0.033 to -2.169), and 0.1569 µg mL-1 respectively, the calibration graphs were linear in the concentration range of (2.0-200µg ml-1), the . molar absorptivity (5937.473L mol-1 cm-1) The proposed methods were successfully applied for the determination of uric acid in serum and urine samples for twenty persons.

General formation of Prussian blue analogue microtubes for high-performance Na-ion hybrid supercapacitors

One-dimensional (1D) hollow-structured nanomaterials with desirable compositions have aroused huge attention in the field of electrochemical energy storage. In the present study, 1D hierarchical cobalt hexacyanoferrate (CoHCF) microtubes were initially fabricated using a facile self-templated method with the electrospun polyacrylonitrile (PAN)-cobalt acetate (Co(Ac)2) as templates. After the chemical reaction was performed between the templates and a potassium ferricyanide solution, the core-shell PAN-Co(Ac)2@CoHCF nanofibers were successfully fabricated. Subsequently, the CoHCF microtubes were finally obtained via the selective dissolution of the PAN-Co(Ac)2 cores. Benefiting from the unique structural characteristic, the CoHCF microtubes electrode exhibited prominent electrochemical characteristics in Na2SO4 aqueous electrolyte, including a high specific capacitance of 281.8 F g−1 (at 1 A g−1), and good rate capability as well as long cycling stability (93% capacitance retention after 5000 cycles). The hybrid supercapacitor assembled with CoHCF microtubes and activated carbon (AC) as the positive and negative electrodes, respectively, exhibited a high energy density of 43.89 W h kg−1, a power density of 27.78 kW kg−1, as well as a long cycle life. Note that this versatile self templated synthetic strategy could be extended to fabricate other 1D hollow Prussian blue (PB) or its analogues (PBA) with controllable composition, which have a potential application in a range of fields.

A magnetically induced fluidized-bed reactor for intensification of electrochemical reactions

High electrochemical conversion rates can be obtained if the ratio of electrode surface to solution volume is maximized. In this context, packed bed electrodes consisting of fine conductive particles offer exceptionally high specific surfaces. However, in case of electrochemical reactions involving suspended solids or gases, packed bed electrodes are not suitable due to the risk of blockage. Fluidized bed electrodes can avoid this risk, but encounter problems regarding the electrical contacting between the electrode particles. In this work, we show that a magnetic stabilization of the fluidized bed electrode improves the contacting of the electrode particles and results in strongly improved yields. With electrode particles having a mean size of 175 µm and consisting mainly of carbon and magnetite, it was found that the yield of the reduction of a 3 mM potassium ferricyanide solution approached 100% when flowing through the fluidized bed with superimposed magnetic field, while the yield was less than 50% without the application of a magnetic field. To achieve this enhancement, the effective electrode surface of the fluidized bed must be increased by up to 400% when applying a magnetic flux density of 20 mT. Our results show that the magnetic stabilization of a fluidized bed electrode significantly improves the usability of this type of electrochemical reactor. We anticipate that the designed reactor will be a starting point for further investigations of applying fluidized bed electrodes for challenging electrochemical processes including solids and gases, as they can be found for example in waste water treatment or electro-biotechnology.

A Microwatt Dual-Mode Electrochemical Sensing Current Readout With Current-Reducer Ramp Waveform Generation.

An electrochemical sensing chip with an integrated current-reducer pattern generator and a current-mirror based low-noise chopper-stabilization potentiostat circuit is presented. The pattern generator, utilizing the current reducer technique and pseudo resistors, creates a sub-Hz ramp signal for the cyclic voltammetric (CV) measurement without large-size passive components. The proposed design adopts the chopper-stabilization and low-noise biasing technique for the potentiostat and a counter-based time-to-digital converter to reduce the amplitude noise effects and to convert the sensing current signal to digital codes for further data processing. The design is fabricated using a 0.18-μm CMOS process and achieves a 41pA current resolution in the current range of ±5μA while maintaining the R2 linearity of 0.998. The system consumes 16μW from a 1.2V supply when a 5μA sensing current is detected. The power efficiency of the readout interface is 0.31, and the sensing current dynamic range is 108dB. The design is fully integrated into a single chip and is successfully tested in the dual-mode (CA/CV) measurements with commercial gold electrodes in a potassium ferricyanide solution in sub-millimolar concentrations.

Wall to Bed Mass Transfer in the Presence of Double Cone Promoter in a Three Phase Fluidized Bed with Conical Entry of Electrolyte

Abstract Investigations have been carried out experimentally to study the effect on wall-to-bed mass transfer coefficient in presence of double cone promoter in a three-phase fluidized bed with a conical entry of electrolyte. The system chosen was an electrolyte as liquid phase, glass spheres of different diameters as solid phase and inert nitrogen as gas phase. The electrolyte was an equimolar solution of potassium ferricyanide and potassium ferrocyanide each of 0.01 N with 0.5 N sodium hydroxide as indifferent electrolyte. The reaction considered was the reduction of ferricyanide ion. The experiment had been carried out at temperature range of 36 to 38 o C at which the physical property values of the electrolyte were known from literature. The mass transfer coefficient was computed from the measured limiting current. It was found that the mass transfer coefficient was relatively independent of liquid velocity within the range covered in the present experiment. The k L increased marginally with increasing gas velocity. The k L was not influenced significantly by particle size and diameter of promoter within the present study range. The entire experimental data have been correlated in terms of Coulburn j D -factor and particle Reynolds number. Keywords: Mass transfer coefficient based on liquid side, k L, Coulburn j D -factor, particle Reynolds number, Rep , Froude number based on gas velocity, Fr g , Schmidt number, Sc

Core-Shell Prussian Blue Analogs with Compositional Heterogeneity and Open Cages for Oxygen Evolution Reaction.

Here, a reduction‐cation exchange (RCE) strategy is proposed for synthesizing Fe–Co based bimetallic Prussian blue analogs (PBAs) with heterogeneous composition distribution and open cage nanocage architecture. Specially, bivalent cobalt is introduced into a potassium ferricyanide solution containing hydrochloric acid and polyvinyl pyrrolidone. The uniform PBAs with opened cages are formed tardily after hydrothermal reaction. Time‐dependent evolution characterization on composition elucidating the RCE mechanism is based on the sequential reduction of ferric iron and cation exchange reaction between divalent iron and cobalt. The PBA structures are confirmed by electron tomography technology, and the heterogeneous element distribution is verified by energy‐dispersive X‐ray spectroscopy elemental analysis, leading to the formation of core–shell PBAs with compositional heterogeneity (Fe rich shell and Co rich core) and open cage architecture. When the PBA catalysts are used to boost the oxygen evolution reaction (OER), superior OER activity and long‐term stability (low overpotential of 271 mV at 10 mA cm−2 and ≈5.3% potential increase for 24 h) are achieved, which is attributed to the unique compositional and structural properties as well as high special surface areas (576.2 m2 g−1). The strategies offer insights for developing PBAs with compositional and structural multiplicity, which encourages more practical catalytic applications.

Porous tal palm carbon nanosheets: preparation, characterization and application for the simultaneous determination of dopamine and uric acid.

A novel porous tal palm carbon nanosheet (PTPCN) material was synthesized from the leaves of Borassus flabellifer (tal palm) and used for developing an electrochemical sensor through modifying a glassy carbon electrode (GCE) simply by drop-casting on it a solution of the material for the sensitive simultaneous detection of dopamine (DA) and uric acid (UA), even in the presence of interfering species. The drop-casting solution was prepared by simply dispersing the PTPCNs in ethanol without using any other binding materials (e.g. Nafion). The surface morphologies of the PTPCNs were studied through field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction spectroscopy (XPS) studies revealed the chemical composition of the PTPCNs' surface. Their structural properties were studied using X-ray diffraction (XRD) and Raman spectroscopy. Brunauer–Emmett–Teller (BET) analysis confirmed the surface area and pore volume to be 1094.53 m2 g−1 and 0.74 cm3 g−1, respectively, while Barrett–Joyner–Halenda (BJH) pore-size distribution showed the average pore size to be 22 nm. The sufficiently large surface area and pore-size distribution suggested better electrocatalytic properties compared to the average modifying materials. The modified electrode (PTPCNs/GCE) was characterized through impedimetric and CV techniques in standard potassium ferricyanide solution for evaluating their charge-transfer resistance and electrochemical properties. The limits of detection (S/N = 3) were 0.17 μM and 0.078 μM and the sensitivities were 1.2057 μA μM−1 cm−2 and 2.693 μA μM−1 cm−2 for UA and DA, respectively. The possible interactions that took place between the PTPCNs and the analytes that aided in the enhancement of the electroanalytical performance of the PTPCNs/GCE are discussed based on the experimental findings and established theoretical concepts. The PTPCNs/GCE was successfully employed for analyzing real samples, like dopamine injection and urine.

The light triggered dissolution of gold wires using potassium ferrocyanide solutions enables cumulative illumination sensing

Electronic systems with on-demand dissolution or destruction capabilities offer unusual opportunities in hardware-oriented security devices, advanced military spying and controlled biological treatment. Here, the dissolution chemistry of gold, generally known as inert metal, in potassium ferricyanide and potassium ferrocyanide solutions has been investigated upon light exposure. While a pure aqueous solution of potassium ferricyanide–K3[Fe(CN)6] does not dissolve gold, an aqueous solution of potassium ferrocyanide–K4[Fe(CN)6] irradiated with ambient light is able to completely dissolve a gold electrode within several minutes. Photo activation and dissolution kinetics were assessed at different initial pH values, light irradiation intensities and ferrocyanide concentrations. Addition of small amounts of the heavy metal thallium (260 ppb) also provides tunability of the dissolution kinetics. An investigation of the involved chemical and physical processes of photochemistry, cyanide diffusion and surface reaction results in an understanding of the rate limiting steps and yields an overall transformation of irradiated light energy to dissolved gold of 2.6%. A potential application of this novel gold dissolution method as a cumulative light sensor is demonstrated and discussed.