Revisiting the Response Mechanism of Polymeric Membrane Based Heparin Electrodes

Potentiometric membrane electrodes that respond to heparin and other polyanions were introduced in the early 1990s. Herein, the mechanism of polymer membrane electrode type heparin sensors is revisited. The extraction/diffusion of heparin is studied via both potentiometric and impedance spectroscopic techniques using a prefractionated heparin preparation that contains polyanionic species >10 000 Daltons. The reversal in EMF response using this heparin preparation indicates diffusion of higher MW heparin fragments to the backside of the membrane. Diffusion coefficients are calculated using a novel formula derived from the phase boundary potential model and Fick′s second law of diffusion. Impedance spectroscopy is also employed to show that high MW heparin species are extracted and diffuse across the PVC membranes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90404/1/53_ftp.pd

The Influence of Thermal Crosslinking on Solubility of Films Prepared from Collagen Hydrolysate

The presented work describes a method of utilizing collagen hydrolysate obtained through enzymatic hydrolysis of chrome-tanned shavings for preparing biodegradable films. Films were prepared by casting from a solution of collagen hydrolysate with added plasticizer (glycerol) and cross-linking agent (starch dialdehyde). Films thus prepared were subjected to thermal annealing at 60, 70, 80 and 90 oC for 24 hours. Thermal annealing is a mode of physical cross-linking of biodegradable films. The work studied effect of thermal crosslinking on film solubility. Solubility curves are important for applying biodegradable films in industrial practice. Thermal annealing was found to affect the cross-linking degree of prepared film in significant manner, hence, also, its solubility. Results indicate that collagen hydrolysate, following certain modification by plasticizer and cross-linking agent is capable of producing films whose properties may be additionally modified.RESUMEN: El trabajo presentado describe un método para utilizar una solución de un hidrolizado colagénico por hidrólisis enzimática de rebajaduras de cuero al cromo en la preparación de películas biodegradables. Películas fueron preparadas por vaciado desde una solución del hidrolizado colagénico con un plastificante añadido (glicerina) y un agente reticulante (almidón dialdehídico). Las películas así preparadas fueron sometidas a un fraguado térmico de 60, 70, y 90ºC durante 24 horas. Fraguado térmico es un método de reticulación de películas biodegradables. El trabajo estudió el efecto del fraguado térmico sobre la propiedad de solubilidad de la película. Curvas de solubilidad son importantes en las prácticas de aplicación industrial de películas biodegradables. El fraguado térmico, se encontró que afecta en forma significante el grado de reticulación de las películas así preparadas, luego entonces, su solubilidad. Resultados indican que el hidrolizado de colágeno, con consiguientes modificaciones por plastificante y agente reticulante, es capaz de producir películas cuyas propiedades pueden ser adicionalmente modificadas

REMOVAL OF DIQUATERNARY AMMONIUM CATIONS FROM AS-SYNTHESIZED SSZ-16 ZEOLITE

Zeolites are stable microporous aluminosilicates with numerous applications in chemical technology such as separation of species and catalytic transformations. Our study is focused on a weakly explored zeolite SSZ-16 with pore constrictions defined by 8-membered oxygen rings. Key results are the preparation of Et6-diquat-5 dication used as a structure directing agent (SDA) and finding the optimum synthesis conditions with respect to zeolite phase purity. Stability of SDA was examined in conditions similar to those of autoclave synthesis (concentration, pH, temperature). Moreover, the content and location of SDA species in zeolite phase and conditions of SDA decomposition were investigated

REMOVAL OF DIQUATERNARY AMMONIUM CATIONS FROM AS-SYNTHESIZED SSZ-16 ZEOLITE

Zeolites are stable microporous aluminosilicates with numerous applications in chemical technology such as separation of species and catalytic transformations. Our study is focused on a weakly explored zeolite SSZ-16 with pore constrictions defined by 8-membered oxygen rings. Key results are the preparation of Et6-diquat-5 dication used as a structure directing agent (SDA) and finding the optimum synthesis conditions with respect to zeolite phase purity. Stability of SDA was examined in conditions similar to those of autoclave synthesis (concentration, pH, temperature). Moreover, the content and location of SDA species in zeolite phase and conditions of SDA decomposition were investigated

Electrochemical evidence of catalysis of oxygen reduction at the polarized liquid–liquid interface by tetraphenylporphyrin monoacid and diacid

Cyclic voltammetry is used to study the role of 5,10,15,20-tetraphenyl-21H,23H-porphine (H2TPP) in the reduction of molecular oxygen by decamethylferrocene (DMFc) at the polarized water|1,2-dichloroethane (DCE) interface. It is shown that this rather slow reaction proceeds remarkably faster in the presence of tetraphenylporphyrin monoacid (H3TPP+) and diacid (H4TPP2+), which are formed in DCE by the successive transfer of two protons from the acidified aqueous phase. A mechanism is proposed, which includes the formation of adduct between H3TPP+ or H4TPP2+ and O2 that is followed by electron transfer from DMFc to the adduct leading to the observed production of DMFc+ and to the regeneration of H2TPP or H3TPP+, respectively

Pulsed chronopotentiometric membrane electrodes based on plasticized poly(vinyl chloride) with covalently bound ferrocene functionalities as solid contact transducer

Ion-selective membrane materials based on poly(vinyl chloride) (PVC)-containing covalently attached redox-active ferrocene (Fc) groups are characterized here as all-solid-state pulsed voltammetric ion sensors. The redox capacity of the membrane increases 7-fold with a doubling of the Fc content and 3-fold with the addition of 10 wt % of the lipophilic electrolyte ETH 500, tetradodecylammonium tetrakis(4-chlorophenyl) borate. This salt improves the ionic conductivity of the membrane and appears to make the Fc groups electrochemically more accessible. A too high content of the two, on the other hand, was found to cause undesired sensitivity to redox-active species present in the sample solution. Dilution of the membrane with a plasticizer eliminated this redox sensitivity while preserving its high redox capacity. A practical application of the designed electrodes in electrochemical analysis was demonstrated with a multi-pulse protocol that includes a current-controlled ion uptake pulse, followed by an open-circuit potential (OCP) measurement and a regeneration pulse. Potentiometric calibration curves obtained with this protocol exhibited a linear response with near-Nernstian slopes for acetate, nitrate, chloride, and perchlorate ions with the selectivity expected for an ion-exchanging membrane