Separation of Dopamine and Epinephrine by a Novel Electrophoresis Technique with Nafion Membrane as Separation Column

A novel electrophoresis technique, in which a strip of perflurosulfonic-acid (nafion 117) membrane was used to replace the conventional separation column and liquid buffer solution within, was developed and employed to separate the mixture of dopamine and epinephrine under a low separation voltage of 100 V with quadruple pulses amperometry detection. It was showed that the so-called Nafion membrane electrophoresis could be one of very simple and easy method and has the potentiality to be used to separate and analyze some small organic biologic molecules. Key words nafion membrane - electrophoresis - electrochemical detector - dopamine - epinephrine CLC number O 657. 7 Foundation item: Support by the Foundation of Electroanalytical Chemistry Open Lab (203231510), Changchum, China.Biography: Fang Cheng (1971-), male, Lecture, Ph. D, research direction: Electroanalysis.

Photophysical Behaviors of Azobenzene in Solvent-Swollen Nafion Membranes

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The removal of inevitable NOx species in catalysts and the selection of appropriate membrane for measuring electrocatalytic ammonia synthesis accurately

Ammonia synthesis by electrocatalytic nitrogen reduction reaction(NRR)is considered as a promising alternative to the Haber−Bosch process.However,due to the extremely low ammonia yield and easily accessible extraneous contamination in the laboratory,NRR study always suffers from fluctuation and variability.Finding and eliminating all kinds of possible extraneous contamination is crucial to evaluate the performance of electrocatalytic ammonia synthesis accurately.In this work,we systematically explored two factors that affect NRR results but are easy to be ignored:the selection of membrane for NRR and the unconscious N-source in NRR catalysts.After series of experiments,we proposed a low-cost and almost pollution-free Celgard 3501 membrane as the separator for NRR to avoid the adsorption and release of ammonia by the membrane.In addition,we proposed a pre-reduction strategy to remove residual or adsorbed NOx contaminants in catalysts.These two solutions will help the community to evaluate the NRR activity more accurately.

Monitoring of Anthocyanins and Colour in Electrochemically Processed <i>Hibiscus sabdariffa</i>Juice

The vital role of anthocyanins in Hibiscus sabdariffa L. is now known to most consumers. The richness of anthocyanins in antioxidants, vitamin C, minerals, etc., provides Hibiscus juice with proven nutritional qualities. The health requirements of recent years have made food products with added preservatives or processed at high temperatures less popular, thus explaining the new orientations towards innovative and interdisciplinary technologies. Anthocyanins from Hibiscus sabdariffa L. are, however, sensitive to degradation factors such as temperature, light, enzymes and also oxygen. The instability of anthocyanins has long been a subject of research using classic techniques such as heat treatment, the results of which are often limited by the rapid degradation and above all the destruction of the nutritional and organoleptic qualities of the product. Oxygen dissolved in juices is so far treated by bubbling with an inert gas or by adding other molecules such as preservatives which can cause a lot of health damage. The electrochemical approach is a new stabilisation technique that reduces the dissolved oxygen in the juice, cold and without the addition of other molecules. The electrolysis of Hibiscus juice was carried out by noble electrodes (Platinum and Stainless Steel) with a well-characterised Time/Potential or Time/Intensity couple. The electroreduced samples and the control were then stored at 4°C, 25°C and 37°C for more than 6 months. Monitoring of anthocyanins in the first month, of the samples and the control, showed a significant difference of 10% between the electroreduced extract and the untreated control at 37°C, which had previously been problematic for the heat treatment and even for the other membrane techniques. Oxygen reduction on the platinum electrode/ECS allowed the retention of more than 10% of anthocyanins after 4 weeks of storage at 25°C and 37°C. At 4°C, a significant difference of 5% between the electro-reduced Hibiscus juice and the control was maintained until the fifth month of storage with the 1/5 ratio (calyx/water). Non-significant losses in anthocyanin (10 mg/l), for the juice with reduced dissolved oxygen, were noted for the 1/5 and 1/15 ratios during the first month of storage at 4°C against 24 mg/l of significant losses for the 1/20 ratio. However, the untreated control showed significant losses for the ratios 1/20, 1/15 and 1/5. Oxygen dissolved in the juice therefore considerably degrades the anthocyanins of Hibiscus sabdariffa L. from the first month of storage at 4°C.

Modified Nafion Polymer Electrolyte Membranes by 7-Ray Irradiation Used in Direct Methanol Fuel Cells

Modification of the commercial polymer electrolyte membrane(PEM) Nafion 117 byγ-ray irradiation to produce an improved proton exchange membrane for direct methanol fuel cells(DMFCs) was described.The Nafion 117 membrane was exposed under 7-ray irradiation circumstance with the irradiation doses from 10~3 to 10~5 Gy.Subsequently the properties of the membrane itself,in terms of swelling ratio,water uptake rate, proton conductivity and methanol permeability,together with the performance of its membrane electrode assembly (MEA) in DMFC were analyzed and contrasted with the untreated material.When the Nafion 117 membrane was exposed underγ-ray irradiation circumstance,the degradation and crosslinking reactions occurred at the same time.Specific scopes of theγ-ray irradiation dose may cause the membrane crosslinking,thus reduce the membrane swelling ratio and decrease the methanol crossover.By reducing the membrane swelling ratio and methanol permeation,the single DMFC with the modified Nafion 117 membrane produced reasonable power density performance as high as 32 W/m^2 under 2 mol/L methanol solution at room temperature.

Nafion-Induced Metal-Metal Interactions in a Platinum(II) Terpyridyl Acetylide Complex:a Luminescent Sensor for Detection of Volatile Organic Compounds

The platinum(II) terpyridyl acetylide complex [Pt(terpy)(C≡CR)]ClO4 (terpy=2,2'∶6'2''-terpyridine, R=CH2CH2CH3) (1) was incorporated into Nafion membranes. At high loading the dry membranes exhibit intense photoluminescence with max at 707 nm from the 3MMLCT state, which was not observed in fluid solution. Upon exposure to the vapor of polar volatile organic compounds (VOC), this photoluminescence was significantly red-shifed. This process was fully reversible when the VOC-incorporated membrane was dried in air. The dramatic and reversible changes in the emission spectra made the Nafion-supported complex as an interesting sensor candi-date for polar VOC.

Nitrogen-rich Graphdiyne Film for Efficiently Suppressing the Methanol Crossover in Direct Methanol Fuel Cells

The inhibition of the methanol crossover is one of the intractable challenges in the direct methanol fuel cell.The graphdiyne(GDY)with atomic-level pores shows great potential in realizing the zero-permeation of methanol molecules.In this paper,an ultrathin layer of nitrogen-rich GDY film with a high nitrogen content is largely prepared and readily used for retarding the methanol permeation in the state-of-the-art commercial Nafion membrane.The high N-content in this porous GDY nanofilm remarkably increases the selective suppression in methanol transfer,and single-layer GDY film can efficiently prevent 43%methanol crossover and the value of the double-layer GDY film can be high up to 69%.The power performance and the long-term stability of the cell are obviously improved due to the reduced methanol crossover.

Printing ionic polymer metal composite actuators by fused deposition modeling technology

In this work,we printed a Nafion precursor membrane by fused deposition modeling(FDM)rapid prototyping technology and further fabricated IPMCs by electroless plating.The ion-exchange capacity of the Nafion membrane was tested,and the morphology of IPMCs was observed.The electro-mechanical properties of IPMCs under AC voltage inputs were studied,and grasping experiments were performed.The results show that the Nafion membrane after hydrolysis has a good ion-exchange ability and water-holding capacity.SEM observed that the thickness of the IPMC’s electrode layer was about 400 nm,and the platinum layer was tightly combined with the substrate membrane.When using a square wave input of 3.5 V and 0.1 Hz,the maximum current of IPMCs reached 0.30 A,and the displacement and blocking force were 7.57 mm and 10.5 mN,respectively.The new fabrication process ensures the good driving performance of the printed IPMC.And two pieces of IPMCs can capture the irregular objects successfully,indicating the feasibility of printing IPMCs by FDM technology.This paper provides a new and simple method for the fabrication of three-dimensional IPMCs,which can be further applied in flexible grippers and soft robotics.

Cathode catalysis performance of SmBaCuMO_(5+δ) (M=Fe, Co, Ni) in ammonia synthesis

The SmBaCuMO5+δ (M=Fe, Co, Ni) (SBCM) powders were synthesized by the citrate sol-gel method and the powders were sintered to ceramic pellets. The powders and sintered ceramic pellets were characterized with XRD, TEM and SEM measurements. The cathode catalytic performances of SBCM ceramic pellets for ammonia synthesis were studied from wet hydrogen and dry nitrogen at atmospheric pressure and low temperature, using SBCM ceramic pellets as cathode, Nafion proton exchange membrane as electrolyte, Ni-Ce0.8Sm0....