Tubular Exchange Research Articles

Functionalization of High-Density Polyethylene Capillaries for Open Tubular Ion Chromatography.

Ion chromatography is the anion analysis benchmark. A miniature form, Open Tubular Ion Chromatography (OTIC), has attractive attributes for efficient ion separations. Here, we fabricate and characterize high-density polyethylene (HDPE) open tubular anion exchange columns (OTCs). We attach positively charged latex particles onto negatively charged capillary surfaces. For efficient OTIC, column diameters need to be < ∼20µm; functionalizing the bore is challenging. Methods to introduce acid groups to an HDPE capillary bore, e.g., sulfonation using chlorosulfonic or sulfuric acid solutions, with or without grafting of an aromatic ring through photo- or chemical grafting first, are explored. Following quaternary ammonium latex attachment, the ion exchange capacity and separating abilities of each OTC were measured as an index of OTC performance. Gradual loss of capacity was observed for many of these; high-resolution mass spectrometry confirmed the leaching of detached oxidized/sulfonated oligomeric fragments and consequent poisoning of the latex sites. Ways to ameliorate this and/or to rejuvenate the columns are also described.

Production of Novel Tubular Electrochemical Hydrogen Compressor

For most applications, especially transport, hydrogen needs to be compressed due to its low volumetric density. Conventionally, mechanical compressors are used for hydrogen compression, but they possess disadvantages such as high maintenance due to moving parts and a limited one-stage compression ratio. A promising technology to overcome those obstacles is electrochemical hydrogen compression, in which hydrogen is compressed in an electrochemical membrane reactor.To date, only planar electrochemical reactors for hydrogen compression have been investigated although tubular designs offer advantages in membrane area to reactor volume ratio, sealing options, pressure stability and reactor complexity. However, high contact and membrane resistances and scalable manufacturing processes are still challenges to be addressed for the advent of tubular electrochemical compressors in application.Herein we introduce a manufacturing process for tubular electrochemical hydrogen compression reactors. The developed cell comprises a catalyst coated porous tubular anode covered by a tubular proton exchange membrane, which was subsequently coated with the cathode catalyst layer. The porous anode was prepared via metal 3D printing. 3D printing enables tailored porosity and geometry by which mass transport is enhanced. The catalyst layer was applied by manual spray coating. Constant current experiments and electrochemical impedance spectroscopy were performed to characterize the as prepared tubular electrochemical compressor. The results revealed the importance of tailored contacting concepts and the optimization of components regarding water transport, as the efficiency of the process is dominated by contact and membrane resistances.

The Impact of the Nitric Oxide (NO)/Soluble Guanylyl Cyclase (sGC) Signaling Cascade on Kidney Health and Disease: A Preclinical Perspective

Chronic Kidney Disease (CKD) is a highly prevalent disease with a substantial medical need for new and more efficacious treatments. The Nitric Oxide (NO), soluble guanylyl cyclase (sGC), cyclic guanosine monophosphate (cGMP) signaling cascade regulates various kidney functions. cGMP directly influences renal blood flow, renin secretion, glomerular function, and tubular exchange processes. Downregulation of NO/sGC/cGMP signaling results in severe kidney pathologies such as CKD. Therefore, treatment strategies aiming to maintain or increase cGMP might have beneficial effects for the treatment of progressive kidney diseases. Within this article, we review the NO/sGC/cGMP signaling cascade and its major pharmacological intervention sites. We specifically focus on the currently known effects of cGMP on kidney function parameters. Finally, we summarize the preclinical evidence for kidney protective effects of NO-donors, PDE inhibitors, sGC stimulators, and sGC activators.

Functionalized Cycloolefin Polymer Capillaries for Open Tubular Ion Chromatography.

We describe novel cycloolefin polymer (COP)-based open tubular capillary ion exchange columns. COP capillaries (inner diameter of 19-28 μm) were successfully sulfonated at room temperature using a cocktail of ClSO3H (85-95% w/w) and HOAc or H2SO4. The cation exchange capacity is controlled by the sulfonation time and the sulfonation solution composition and can be as high as 300 pequiv/mm2. Following sulfonation, the capillaries were coated with 65-nm-diameter anion exchanger (AEX) latex nanoparticles that attach electrostatically. The typical anion exchange capacities were ∼20 pequiv/mm2. The chromatographic behavior of the AEX latex-coated COP capillaries are greatly dependent on the degree of sulfonation. When the base is heavily sulfonated, neutrals elute after the anions. The position of the water dip varies with the degree of sulfonation; the elution order is normal (water dip appear before anions) only with lightly sulfonated columns. On silica (-SiOH) or poly(methyl methacrylate) (-COOH) surfaces, AEX latex attachment is not stable over long periods in significant concentrations of strong base (e.g., ≥10 mM NaOH). Latex attachment on sulfonated COP surfaces are much stronger; several types show sufficient binding to be used over long periods at practical eluent concentrations, paving the way for suppressed hydroxide eluent ion chromatography (IC), which is discussed in a companion paper. Another interesting feature of COP capillaries lies in their flexibility. If softened at modestly elevated temperatures (e.g., boiling water), they can be coiled down to <1 mm coil radii, revealing, for the first time, the beneficial effects, albeit small, of centrifugal force on mass transfer in open tubular columns.

Polymethylmethacrylate Open Tubular Ion Exchange Columns: Nondestructive Measurement of Very Small Ion Exchange Capacities

We describe an approach to prepare an open tubular ion exchange (OTIE) column by coating a monolayer of anion exchange nanoparticle to a 16-20 μm bore polymethylmethacrylate (PMMA) capillary. The latex nanoparticle was electrostatically attached to carboxylate groups on the inner wall of capillary, pretreated with strong base for hydrolyzing the ester. Several approaches to nondestructively measure ion exchange capacities (IEC) of the columns were examined: (a) adsorption-desorption of an intensely fluorescent ion, e.g. fluorescein, and off-line fluorometry, (b) loading a weakly retained ion (e.g., IO3(-)), frontal displacement by a strongly bound ion (e.g., Cl(-)), and online optical or conductometric boundary detection, and (c) similar to the above except displacement being accompanied by reaction (e.g., acid-base titration). To our knowledge, this is the first time on-column titration has been used to measure capacities. By using different pH displacer solutions, we demonstrate for the first time the possibility of pKa-differentiated ion exchange capacity measurements. The cation exchange capacity of bare PMMA capillaries was on the order of 1 pequiv/mm(2) with little dependence on time and temperature of hydrolysis conditions. After AS18 latex coating, the strong base anion exchange capacity was on the order of 10 pequiv/mm(2), very close to what would be estimated on the basis of monolayer coverage of the surface by individual latex particles. The latex used contained a significant, additional amount of weak base character, about the same as the strong base ion exchange capacity.

Feature and Applications of “EDCORE”

Unlike the conventional flat membrane, the tubular ion exchange membrane “EDCORE” can stand unsupported. It has sufficient mechanical strength for use in electro-deposition electrode diaphragms, and possesses electrochemical properties equivalent to or better than those of the flat ion exchange membrane. We developed an electro-deposition electrode chamber consisting of tubular ion exchange membranes and it had a good reputation with our customers for long time.This paper describes the characteristics of our tubular ion exchange membrane and the applications for electro-deposition of our electrode chamber.

Multilayer chitosan-based open tubular capillary anion exchange column with integrated monolithic capillary suppressor

We describe a multilayered open tubular anion exchange column fabricated by alternately pumping solutions of chitosan and glutaraldehyde. The column is terminated in an integrally bonded monolithic suppressor cast around a mandrel of a tungsten wire, composed of an acrylic acid (AA)–ethylene dimethacrylate (EDMA) monolith that is made with sufficient porogen for the monolith to function as a membrane. For a 4.5 m long 75 μm bore column coated with 24 successive layers of the condensation polymer (estimated to contain ∼72 molecular layers) and coupled to 1 cm length of a suppressor fabricated with 55–60% AA, effective separation of several common anions (F −, Cl −, NO 2 −, Br −, NO 3 −, average number of theoretical plates ∼12,000) and adequate suppression of 1 mM KOH used as eluent was observed at a flow rate of 800 nL min −1 to obtain sub-picomol detection limits at an operating pressure of ∼1 bar. The separation is not time efficient but the system can be meritorious in unique niche applications where a small form factor is desired and liquid volume and power consumption are more important than separation speed.

Use of disposable open tubular ion exchange pre-columns for in-line clean-up of serum and plasma samples prior to capillary electrophoretic analysis of inorganic cations

A simple analytical system using disposable, open-tubular ion exchange clean-up precolumns coupled in-line to capillary electrophoresis for direct injection of biological samples is presented. The clean-up precolumns were prepared from fused silica capillaries by thermally initiated layer-by-layer polymerization of poly(butadiene-maleic acid) (PBMA) directly on the capillary wall. Typically, 6 cm long precolumns with 4-layers of PBMA were used for sample pretreatment. A robust and reproducible coupling between the precolumn (75 μm ID) and the analytical capillary (50 μm ID) was achieved using an inexpensive, commercially available low dead volume union. No extra dispersion of the analyte zones was observed. Proteins and other high molecular weight compounds from biological sample matrices were retained on the cation-exchanger sites of the precolumn, which eliminated their adsorption on analytical capillary walls and ensured stable electroosmotic flow and migration times of target analytes. Unretained small inorganic cations migrated freely into the analytical capillary for separation and detection. Applicability of the sample clean-up procedure was proved by determination of major inorganic cations in blood serum and plasma samples using capillary electrophoresis with contactless conductivity detection. Separations were performed in background electrolyte solution consisting of 15 mM l-arginine, 12.5 mM maleic acid, 3 mM 18-crown-6 at pH 5.5 and repeatabilities of migration times and peak areas were below 1.5% and 7.3%, respectively. Less than 1 μL of biological sample was required for injection.

Prediction of Flow-Induced Vibrations in Tubular Heat Exchangers—Part II: Experimental Investigation

It has become evident that the modeling of the complex dynamics of fluidelastic forces that give rise to vibrations of tube bundles requires a great deal of experimental insight. Accordingly, the prediction of the flow-induced vibration due to unsteady cross-flow can be greatly aided by semi-analytical models, in which some coefficients are determined experimentally. A laboratory test rig with an instrumented test bundle is constructed to measure the fluidelastic coefficients to be used in conjunction with the mathematical model derived in Part I of this paper. The test rig admits two different test bundles, namely, the inline-square and 45deg rotated-square tube arrays. Measurements were conducted to identify the flow-induced dynamic coefficients. The developed scheme was utilized in predicting the onset of flow-induced vibrations in two configurations of tube bundles, and results were examined in the light of Tubular Exchange Manufacturers Association (TEMA) predictions. The comparison demonstrated that TEMA guidelines are more conservative in the two configurations considered.

Gravity‐flow open tubular cation chromatography

We describe ion chromatography (IC) on open tubular cation exchange columns with a controllable capacity multilayered stationary phase architecture. The columns of relatively large bore (75 microm id) are fabricated by coating fused-silica capillaries with multiple layers of poly(butadiene-maleic acid) (PBMA) copolymer and crosslinking the deposited layers by thermally initiated radical polymerisation. Column capacity increases in a predictable manner with increase in the number of successively coated layers. Gravity flow with a modest head (< 2 m) can provide the desired separations within a reasonable period. We provide a minimalist configuration where no suppression is used, the sample is injected hydrodynamically as in CE, and detection is accomplished by an inexpensive homebuilt contactless conductivity detector or a capacitance to voltage digital converter. A 1 m long 75 microm bore column coated with two layers of PBMA allows gravity-flow open tubular IC to separate four alkali cations in < 10 min with a 1 mM tartaric acid (TA) eluent. Simultaneous separation of alkali and alkaline earth metal cations can be accomplished in less than 25 min using 1.75 mM pyridinedicarboxylic acid as an eluent. Contactless conductometric detection (C(4)D) allows LODs down to 150 nmol/L, corresponding to 30 fmol injections. Analysis of real water samples is demonstrated.

Open Tubular Anion Exchange Chromatography. Controlled Layered Architecture of Stationary Phase by Successive Condensation Polymerization

The preparation and performance of a multilayered stationary phase for open tubular anion exchange chromatography in relatively large bore (75 microm diameter) columns are described. The inner surface of a fused-silica capillary tube is coated with up to 25 successive porous polymeric layers formed by condensation polymerization of a primary amine with a diepoxide. Each layer of the anion exchange stationary phase consists of copolymer of methylamine (MA) and 1,4-butanedioldiglycidyl ether (BDDE). The polymer layers are sufficiently porous or permeable; each successive layer of the stationary phase incrementally increases the observed column capacity and chromatographic performance in the open tubular mode. Even though the column inner diameter is far from optimum for open tubular liquid chromatography, we demonstrate the baseline separation of a suite of inorganic anions (F-, Cl-, NO2-, Br-, NO3-) in a 5 m x 75 microm column coated with 25 layers of the anion exchange polymer using 1 mM KOH eluent and suppressed contactless conductometric detection at a flow rate of 1 microL/min (operating pressure of approximately 1 bar) with a plate count of >30,000. Strategies for construction of microsuppressor devices used in open tubular ion chromatography are discussed.

Fabrication of Support Tubular Proton Exchange Membrane For Fuel Cell

The support tubular proton exchange membranes (STPEMs) were fabricated successfully by impregnating porous silica pipe into a solution of perfluorinated resin. The structures of the inner, outer, and cross section of support PEM tube were characterized intensively by scanning electron microscopy observation. In addition, the conductivity and impermeability were measured by electrochemical impedance spectroscopy (EIS) and the bubble method, respectively. Results show that the conductivity of the PEM can reach as low as 1.46S∕m when using the silica pipe of 0.7mm wall thickness. Subsequently, the ST membrane electrode assembly for direct methanol fuel cell (DMFC) and proton exchange membrane fuel cell (PEMFC) applications was prepared first by loading Pt∕C and Pt–Ru∕C catalyst ink onto the outer and inner surfaces of the PEM tube, respectively. The performances of the tubular DMFC and the PEMFC were tested on a self-made apparatus, which shows that the power density of tubular DMFC can reach 10mWcm−2 when 4molL−1 methanol solution flows through the anode at 80°C, and that the power density of tubular PEMFC can reach up to 60mWcm−2 when hydrogen flows at the rates of 20mlmin−1 through the anode at 60°C, both the cathodes adopting air-breathing mode.

Advanced treatment of swine wastewater by electrodialysis with a tubular ion exchange membrane

ABSTRACTTo remove the excess nitrogen and phosphorus in swine wastewater, an electrodialysis technique was applied to an advanced treatment method. The laboratory‐scale swine wastewater treatment system constructed for the present study consisted of an activated sludge process, as the main treatment unit, and electrodialysis, as an advanced treatment unit. This system was operated for 200 days and the processing performance was evaluated. By electrodialysis, approximately 99% of NO3– and PO43– in the activated sludge‐treated water (AT solution) was removed during operation. Furthermore, electrodialysis decreased the color density of the AT solution at a rate of 58%. The advanced treatment of swine wastewater by electrodialysis proved to be an efficient technique to remove excess nitrogen and phosphorus, and decrease color density.

Fast separations with open tubular ion exchange capillary columns

AbstractFused silica columns of 4.6 μm i.d. were coated with 3‐sulfopropylsilane as a cation exchanger and 3‐(2‐aminoethyl‐amino)‐propylsilane as an anion exchanger. Fast separations of cations (&lt; 25 seconds) and of anions (&lt; 35 seconds) were obtained, using a potentiometric microelectrode as a detector. In proceeding towards smaller i.d.s, a mixture of alkali metal cations could be separated successfully in an uncoated fused silica capillary of 2.3 μm i.d. as a result of retention by the surface silanol groups at pH 9.4.

Lithium-Sodium Countertransport: Physiological Moorings for Red Cell Transport Disorders in Hypertension

Erythrocyte lithium-sodium countertransport, a mode of ouabain-insensitive monovalent cation metabolism, is increased in human essential hypertension, but no pathophysiological link to hypertension has yet been established. Similarities between red cell lithium-sodium countertransport and renal proximal tubular sodium-hydrogen ion exchange suggest a possible role for a countertransport analogue in the control of proximal fluid reabsorption. To test this hypothesis, we measured red cell countertransport and renal lithium clearance, a reliable measure of proximal tubular sodium reabsorption, in normotensives and hypertensives. We found that lithium clearance is (a) inversely correlated with red cell countertransport, (b) decreased in essential hypertensives (reflecting increased proximal sodium reabsorption), and (c) lower in normotensive subjects with a family history of hypertension than in those without such a history. The mechanism by which enhanced proximal tubular sodium reabsorption is related to essential hypertension is unknown, but in addition to its connection to lithium clearance, red cell countertransport is correlated with total peripheral resistance and diastolic compliance of the left ventricle. It is therefore possible that alterations of transport demonstrated in red cells reflect generalized membrane characteristics shared by cardiovascular and renal tissues. Measurements of lithium clearance provide a useful tool for further characterizing the control of renal proximal tubular fluid reabsorption in hypertension. Studies using these measurements may help to explain mechanisms of salt sensitivity and differential responses to antihypertensive therapies as well as yield insights into the heritable basis of human hypertension.

Ion penetration through tubular ion exchange membranes

Etude sur du polytetrafluoroethylene, polyacetate d'ethyl vinyle et polyperfluorosulfonate. Influence de la taille et de la charge de l'ion

Tubular interpolymer ion exchange membranes 1. Cation exchange membranes based on polyethylene modified with styrene‐divinylbenzene copolymers

AbstractTubular cation exchange membranes were prepared from the system polyethylene/poly(styrene‐co‐divinylbenzene) [PE/poly(St‐co‐DVB)] by extruding tubes followed by their sulfonation with a solution of chlorosulfonic acid in 1,2‐dichloroethane. The content of DVB in the system PE/poly(St‐co‐DVB) as well as the parameters of extrusion and sulfonation were varied. The best properties for the use in the Donnan dialysis had membrane tubes containing 4 wt.‐% of DVB in the aromatic component of the polymer system, sulfonated with a 20 vol.‐% solution of chlorosulfonic acid for 6 h.

Hemodynamic characterization of hypertension induced by chronic intrarenal or intravenous infusion of norepinephrine in conscious rats.

The present study was designed to determine the hemodynamic changes underlying the hypertension induced by chronic intrarenal infusion of norepinephrine (NE) in conscious rats. NE was infused for a 5-day period intrarenally with osmotic minipumps via a chronic catheter in the right suprarenal artery at rates of 4 and 36 micrograms . kg-1 . hr-1 or intravenously at a rate of 36 micrograms . kg-1 . hr-1. Control rats received a 1 microliter . hr-1 intrarenal infusion of pyrogen-free 0.9% NaCl. In separate experiments, short-term effects were measured continuously during a 22- to 24-hour intrarenal infusion of 4 and 36 micrograms NE . kg-1 . hr-1 or intravenous infusion of 36 micrograms NE . kg-1 . hr-1. Intrarenal infusion of NE produced a more pronounced long-term hypertensive effect than infusion of the same dose intravenously. This hypertension was characterized by a rapid and sustained increase in total peripheral resistance index (TPRI). Despite of the initial renal vasoconstriction, specifically produced during the first 24 hours of intrarenal NE application, cardiac index (CI) in parallel to stroke volume index (SVI) decreased significantly during intrarenal as well as during intravenous NE infusion. Furthermore, no signs of sodium retention were observed. Both rates of intrarenal NE infusion have been shown previously to produce a significant long-term increase in plasma potassium concentration, and the present study indicates that this is presumably the result of decreased urinary potassium output. It is concluded that chronic hypertension produced by intrarenal or intravenous infusion is not volume-dependent. The relatively greater increase in TPRI during intrarenal NE infusion is attributed to vascular wall receptor sensitization by increased plasma potassium levels resulting from effects of intrarenally present NE on tubular cation exchange mechanisms.

Kidney and urinary bladder functions of the rainbow trout in Mg and Na excretion.

Magnesium concentration in the urinary bladder of marine teleosts is high and [Na] is low. The inverse relationship may be due to the coupling of Mg secretion to Na reabsorption through a common tubular transport system or coupling may be indirect. Unanesthetized sea-water-adapted Salmo gairdneri were infused with saline or MgCl2, and ureteral urine was collected. Over a wide range of Mg excretion rates, tubular Mg secretion and Na reabsorption show no clear correlation as might be expected from an obligatory tubular Mg/Na exchange. Instead ureteral Mg and Na concentrations and excretion rates are positively correlated. These data are not consistent with the presence of a tubular exchange system. When ureteral urine was allowed to remain in the urinary bladder before being analyzed the inverse relationship between [Mg] and [Na] developed because the bladder reabsorbed Na and H2O, thereby concentrating Mg. Hence, tubular Mg/Na exchanges do not produce the inverse Mg/Na relationship in bladder urine. Instead, Mg is secreted in the nephron, while Na and H2O are reabsorbed from the bladder.

Effects of flow rate and potassium intake on distal tubular potassium transfer.

Potassium transport was studied across proximal and distal tubular epithelium in rats on a normal, low- and high-potassium intake during progressive loading with isotonic saline (150 mM) or a moderately hypersomotic urea (200 mM) sodium chloride (100 mM) solution. Free-flow micropuncture and recollection techniques were used during the development of diruesis and tubular fluid (TF) analyzed for inulin-14C, potassium (K) and sodium (Na). Tubular puncture sites were localized by neoprene filling and microdissection. During the large increase in tubular flow rates (10 times): 1) fractional potassium reabsorption fell along the proximal tubule, 2) TFk along the distal tubule remained constant and independent of flow rate in control and high-k rats; thus, net potassium secretion increased in proportion to and was limited by flow rate. 3) In low-K rats TF k fell; with increasing flow rates distal K secretion was not effectively stimulated. 4) Distal tubular sodium reabsorption increased in all animals with flow rate, but tubular Na-K exchange ratios varied greatly. It is suggested that whenever sodium delivery stimulates distal tubular potassium secretion it does so by 1) increasing volume distal tubular potasssium secretion and by 2) augmenting the transepithelial electrical potential difference (lumen negative).