PTFE Tube Research Articles

Artificial Ureter in Patients with Extensive Ureteral Damage.

loss of significant lengths of ureter when substitution with bowel or bladder fails is a disaster in urology. This study is conducted to evaluate the results of subcutaneous nephron-vesical bypass (SNVB) in ureteral damage of different etiologies. Seventeen SNVB were employed in patients with ureteral injuries. We employed a device consisted of an internal silicone tube covered by a coiled PTFE tube to replace the ureter. This is called artificial ureter (AU). Proximal end of the AU was introduced in the kidney percutaneously, the tube was passed through a subcutaneous tunnel, while the distal end was inserted in the bladder through a small suprapubic incision. Follow-up ranged from six months to ten years. We removed the prosthetic ureter in one patient due to gross hematuria two months after insertion. One of the patients was reoperated two days after the procedure because of urinary leakage. In all other patients, the procedure was safe and effective. Subcutaneous nephron-vesical bypass is a safe and appealing alternative to a nephrostomy tube. This is a permanent device with no need for exchange. The technique can be applied in ureteral injuries due to various causes.

Non-proximate mass spectrometry using a heated 1-m long PTFE tube and an air-tight APCI ion source

Direct and rapid trace-level gas analysis is highly needed in various fields such as safety and security, quality control, food analysis, and forensic medicine. In many cases, the real samples are bulky and are not accessible to the space-limited ion source of the mass spectrometer. In order to circumvent this problem, we developed an airtight atmospheric-pressure chemical ionization (APCI) ion source equipped with a flexible 1-m-long, 2-mm-i.d. PTFE sniffing tube. The ambient air bearing sample gas was sucked into the heated PTFE tube (130 °C) and was transported to the air-tight ion source without using any extra pumping system or a Venturi device. Analytes were ionized by an ac corona discharge located at 1.5 mm from the inlet of the mass spectrometer. By using the airtight ion source, all the ionized gas in the ion source was introduced into the vacuum of the mass spectrometer via only the evacuation of the mass spectrometer (1.6 l min−1). Sub-pg limits of detection were obtained for carbaryl and trinitrotoluene. Owing to its flexibility and high sensitivity, the sniffing tube coupled with a mass spectrometer can be used as the stethoscope for the high-sensitive gas analysis. The experimental results obtained for drugs, hydrogen peroxide and small alkanes were discussed by DFT calculations.

Dual thermostating in flow analysis

An advanced strategy involving concentric tubes is proposed for fast and controlled heating (or cooling) of the reaction medium in flow analysis. Different temperatures are set by sequentially circulating two thermostated water streams through the outer larged bore (2.0mm i.d.) silicone tube, which acted as a water-jacket of the inner (0.8mm i.d.) PTFE tube, and directing the sample zone to flow through it. Each end of the outer tube is connected to a three-way valve that selects the stream to flow inside it. For 25–85cm tube lengths and a 12.0mLmin−1 flow rate, the time interval required for temperature attainment, and the uniformity of temperature along the tube were evaluated. For the 85-cm tube, low differences in temperatures along the coil (1.1–8.7°C) and between programmed and attained values (2.3–13.4°C) were noted within a wide range of pre-set temperatures (15–75°C). The feasibility of the innovation in flow analysis was demonstrated in a model system relying on the iodide-nitrite reaction. The strategy allows fast (15–120s) thermostating of the reaction medium in a versatile and simple way, and is especially attractive when two controlled temperatures are set during the analytical course. Potentialities and limitations of the innovation are discussed.

PTFEチューブを分離場とするアミロイド線維の分離分析

PTFEチューブを分離場とするアミロイド線維の分離分析

ChemInform Abstract: Br2F7‐ and Br3F10‐: Peculiar Anions Showing μ2‐ and μ3‐Bridging F‐Atoms.

AbstractMBr3F10 (M: Rb, Cs) and RbBr2F7 are obtained in the reaction of equimolar amounts of MCl and BrF3 (prepared by passing gaseous F2 through liquid Br2) using Freon‐113 as both a moisture protection and coolant for the exothermic reaction (PTFE tube, 98, 97, and 91% yield, respectively).

The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors.

In this paper, a micro-fluidic optimized process for the continuous flow synthesis of azo compounds is presented. The continuous flow synthesis of Sudan II azo dye was used as a model reaction for the study. At found optimal azo coupling reaction temperature and pH an investigation of the optimum flow rates of the reactants for the diazotization and azo coupling reactions in Little Things Factory-MS microreactors was performed. A conversion of 98% was achieved in approximately 2.4 minutes and a small library of azo compounds was thus generated under these reaction conditions from couplers with aminated or hydroxylated aromatic systems. The scaled up synthesis of these compounds in PTFE tubing (i.d. 1.5 mm) was also investigated, where good reaction conversions ranging between 66–91% were attained.

A simple tool for tubing modification to improve spiral high-speed counter-current chromatography for protein purification.

A simple tool is introduced which can modify the shape of tubing to enhance the partition efficiency in high-speed countercurrent chromatography. It consists of a pair of interlocking identical gears, each coaxially holding a pressing wheel to intermittently compress plastic tubing in 0 - 10 mm length at every 1 cm interval. The performance of the processed tubing is examined in protein separation with 1.6 mm ID PTFE tubing intermittently pressed in 3 mm and 10 mm width both at 10 mm intervals at various flow rates and revolution speeds. A series of experiments was performed with a polymer phase system composed of polyethylene glycol and dibasic potassium phosphate each at 12.5% (w/w) in deionized water using three protein samples. Overall results clearly demonstrate that the compressed tubing can yield substantially higher peak resolution than the non-processed tubing. The simple tubing modifier is very useful for separation of proteins with high-speed countercurrent chromatography.

Finite element modeling of continuous-flow microwave heating of fluid foods and experimental validation

In this study, heating of fluid foods in a specially designed continuous-flow microwave heating unit (915 MHz and 5 kW maximum power) was simulated by finite element method using COMSOL Multiphysics. Experiments were then conducted with different test fluids (distilled water, 0.5% and 1% CMC solutions) at different flow rates (1, 2, 3 L/min) to validate the model. The pilot-scale unit consisted of a PTFE tubing which was helically configured within cylindrical cavity of the unit. Cross-sectional temperature distribution at the exit of the tube was measured by specially designed thermocouple system at thirteen points. Numerical and experimental results showed that heating was more uniform for distilled water in comparison to CMC solutions at all flow rates. A comparison of the results of this study to the literature showed that more uniform heating can be achieved for high-viscosity fluid food products by using helical tube in continuous-flow microwave heating systems.

Rapid analysis and identification of meat species by laser-ablation electrospray mass spectrometry (LAESI-MS).

Laser-ablation electrospray ionization mass spectrometry (LAESI-MS) was applied to analyze fresh meat species without sample pretreatment. The study demonstrates that the LAESI-MS technique is a promising, rapid and accurate method for meat identification using a protocol combining principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). A focused IR-laser was used for meat sample ablation at a wavelength of 2940nm. The ablated particulates were carried through a transfer PTFE tube using air as carrier gas, delivered to the electrospray plume and ionized. A TOF-MS was used to detect the ion signal. The raw mass spectra were analyzed using the PCA and PLS-DA protocol. Five fresh meat samples, chicken, duck, pork, beef and mutton, were identified by the developed LAESI-MS technique using the protocol combining PCA and PLS-DA. The discrimination accuracy of all meat species is 100%, and the score plot also shows good identifying ability. Five fresh meat samples were analyzed using the LAESI-MS technique. Each set of raw mass data was collected within 30s and analyzed by the PCA and PLS-DA protocol. Eighteen, 19, 18, 17, and 15 markers for chicken, duck, pork, beef, and mutton, respectively, have been selected successfully for meat identification. The results demonstrate that LAESI-MS is a new reliable and rapid method for meat identification. Copyright © 2016 John Wiley & Sons, Ltd.

The influence of operating conditions on the mass transfer performance of a micro capillary contactor with liquid–liquid slug flow

The application of two-phase slug flows for extraction processes in micro capillaries was investigated and the mass transfer performance under different conditions was analysed. As contacting capillaries PTFE or FEP tubes were used with internal diameters ranging from 0.5mm to 1mm. Two extraction systems were experimentally tested for the evaluation and the extraction efficiencies were measured for various flow rates and slug lengths. In the experiments the slug length was manipulated at a constant flow rate by means of a specially developed slug valve and a complete separation was ensured by a newly designed robust phase separator. Besides single-step experiments, a counter-current microfluidic flow was realised by connecting co-current flow modules in a counter-current arrangement and performance results for a two-stage counter-current operation were also obtained.

Hydrogel-based flexible micro-reference electrodes for use in alkaline and neutral pH solutions

Two types of nonbreakable, flexible micro-reference electrodes filled with gel-electrolytes were prepared for use in solutions with alkaline and neutral pH. The electrodes are intended for electrochemical measurements, in which chloride-free conditions are important. Due to the flexible, bendable construction of the electrodes, electrochemical experiments at locations difficult to access with common reference electrodes are enabled. Hg|HgO-type electrodes were prepared from amalgamated Au wires, followed by oxidation of the amalgam, which is mounted in a PTFE tube filled with 0.1M NaOH solution immobilized in a PAA-g-PEO gel. The potential of this type of electrode was found to be 0.162 ± 0.002 V (SHE) at room temperature. Cu|CuSO4 electrodes, consisting of a Cu wire immersed in a saturated CuSO4 solution jellied with gelatin, showed a stable open-circuit potential of 0.312 ± 0.001 V (SHE). Further characterization of the electrodes was performed in terms of electrochemical impedance spectroscopy and micro-polarization measurements. As an alternative to the flexible electrodes, rigid electrodes in glass enclosure were fabricated in analogy to the flexible-type electrodes.

Determination of clothianidin in food products by using an automated system with photochemically induced fluorescence detection

A flow-through system based on the integration of solid-phase spectroscopic detection implemented with photochemically induced fluorescence (PIF) is proposed for the determination of clothianidin (a non-fluorescent neonicotinoid insecticide) through a multicommutated method. The pesticide is injected into the carrier stream (0.015molL−1C2H4O2/NaC2H3O2, pH=5.0) and flows towards a homemade photoreactor, which consists of a PTFE tubing loosely coiled around a low-pressure mercury lamp (15W). After the photochemical reaction of clothianidin, the generated fluorescent photoproduct is transported to a flow cell packed with Sephadex-SP C-25 where it is retained and monitored (λex=357nm/λem=418nm). The method presents a detection limit of 1.5ngmL−1, a sample throughput of 23h−1 and inter-day relative standard deviation lower than 3%. The described system has been satisfactorily applied to the determination of clothianidin in samples of drinking water, rice and honey. Taking into account that the maximum residue limit specified in the Codex Alimentarius Commission for rice grains is 0.5mgkg−1, recovery experiments have been carried out for clothianidin concentrations in the 0.3-10.0mgkg−1 range.

Separation of proteins by cation-exchange sequential injection chromatography using a polymeric monolithic column.

Since sequential injection chromatography (SIC) emerged in 2003, it has been used for separation of small molecules in diverse samples, but separations of high molar mass compounds such as proteins have not yet been described. In the present work a poly(glycidyl methacrylate-co-ethylene dimethacrylate) (GMA-co-EDMA) monolithic column was prepared by free radical polymerization inside a 2.1-mm-i.d. activated fused silica-lined stainless steel tubing and modified with iminodiacetic acid (IDA). The column was prepared from a mixture of 24% GMA, 16% EDMA, 20% cyclohexanol, and 40% 1-dodecanol (all% as w/w) containing 1% of azobisisobutyronitrile (AIBN) (in relation to monomers). Polymerization was done at 60 °C for 24 h. The polymer was modified with 1.0 M IDA (in 2 M Na2CO3, pH 10.5) at 80 °C for 16 h. Separation of myoglobin, ribonuclease A, cytochrome C, and lysozyme was achieved at pH 7.0 (20 mM KH2PO4/K2HPO4) using a salt gradient (NaCl). Myoglobin was not retained, and the other proteins were separated by a gradient of NaCl created inside the holding coil (4 m of 0.8-mm-i.d. PTFE tubing) by sequential aspiration of 750 and 700 μL of 0.2 and 0.1 M NaCl, respectively. As the flow was reversed toward the column (5 μL s(-1)) the interdispersion of these solutions created a reproducible gradient which separated the proteins in 10 min, with the following order of retention: ribonuclease A < cytochrome C < lysozyme. The elution order was consistent with a cation-exchange mechanism as the retention increased with the isoelectric points.

An improved design of spiral tube assembly for separation of proteins by high-speed counter-current chromatography

A new spiral tube assembly was designed to improve the column capacity and partition efficiency for protein separation. This spiral tube assembly has greater column capacity than the original tubing because of an increase in radial grooves from 4 to 12 to accommodate more spiral layers and 12 narrow spots instead of 4 in each circular loop to interrupt the laminar flow that causes sample band broadening. Standard PTFE tubing (1.6mm ID) and the modified flat-twisted tubing were used as the separation column. The performances of both assemblies were compared for separating three stable test proteins including cytochrome c, myoglobin, and lysozyme using a two phase aqueous–aqueous solvent system composed of polyethylene glycol 1000 (12.5% w/w) and dibasic potassium phosphate (12.5% w/w). All samples were run at 1, 2, 3, and 5mL/min at both 800rpm and 1000rpm. The separation of these three protein samples produced high stationary phase retentions at 1, 2, and 3mL/min, yet separated efficiently at 5mL/min in 40min. After comparing the separation efficiency in terms of the peak resolutions, theoretical plate numbers, and separation times, it was determined that the flat-twisted tubing was more effective in separating these protein samples. In order to validate the efficacy of this novel assembly, a mixture of five protein samples (cytochrome c, myoglobin, ovalbumin, lysozyme, and hemoglobin) were separated, under the optimal conditions established with these three protein samples, at 1mL/min with a revolution speed of 1000rpm. There were high stationary phase retentions of around 60%, with effective separations, demonstrating the efficiency of the flat-twisted spiral tube assembly. The separation time of 6h was a limitation but can potentially be shortened by improving the strength of the column that will permit an increase in revolution speed and flow rate. This novel spiral separation column will allow rapid and efficient separation of mixtures with high yield of the constituent components.

High-Throughput Contact Flow Lithography.

High-throughput fabrication of graphically encoded hydrogel microparticles is achieved by combining flow contact lithography in a multichannel microfluidic device and a high capacity 25 mm LED UV source. Production rates of chemically homogeneous particles are improved by two orders of magnitude. Additionally, the custom-built contact lithography instrument provides an affordable solution for patterning complex microstructures on surfaces.

PTFE-Membrane Flow Reactor for Aerobic Oxidation Reactions and Its Application to Alcohol Oxidation

A “tube-in-shell” membrane flow reactor has been developed for aerobic oxidation reactions that permits continuous delivery of O2 to a liquid-phase reaction along the entire length of the flow path. The reactor uses inexpensive O2-permeable PTFE (“Teflon”) tubing that is compatible with elevated pressures and temperatures and avoids hazardous mixtures of organic vapor and oxygen. Several polymeric materials were tested, and PTFE exhibits a useful combination of low cost, chemical stability and gas diffusion properties. Reactor performance is demonstrated in the aerobic oxidation of several alcohols with homogeneous Cu/TEMPO and Cu/ABNO catalysts (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl and ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl). Kinetic studies demonstrate regimes where the overall rate is controlled by the kinetics of the reaction or the transport of oxygen through the tube wall. Near-quantitative product yields are achieved with residence times as low as 1 min. A parallel, multitube reactor e...

New analytical spiral tube assembly for separation of proteins by counter-current chromatography

A new spiral column assembly for analytical separation by counter-current chromatography is described. The column is made from a plastic spiral tube support which has 12 interwoven spiral grooves. The PTFE tubing of 1.6mm ID was first flattened by extruding through a narrow slit and inserted into the grooves to make 5 spiral layers with about 60ml capacity. The performance of the spiral column assembly was tested with separation of three stable protein samples including cytochrome C, myoglobin and lysozyme in a polymer phase system composed of polyethylene glycol 1000 and dibasic potassium phosphate each at 12.5% (w/w) in water. At 2ml/min, three protein samples were well resolved in 1h. The separation time may be further shortened by application of higher revolution speed and flow rate by improving the strength of the spiral tube support in the future.

Continuous Process for Phase-Transfer-Catalyzed Bisalkylation of Cyclopentadiene for the Synthesis of Spiro[2.4]hepta-4,6-diene

The transfer of a highly exothermic phase-transfer-catalyzed bisalkylation of cyclopentadiene with 1,2-dichloroethane from batch to continuous mode using standard and widely available laboratory equipment is presented. Besides the optimization of the reaction temperature and residence time, the efficient mixing of the organic phase (cyclopentadiene, 1,2-dichloroethane, and MeBu3NCl) and the aqueous phase (30% NaOH) was studied in detail and optimized by the use of a simple, homemade “PTFE Raschig ring static mixer” consisting of a PTFE tube filled with small pieces cut from the same PFTE tube. A flow set-up with two PTFE Raschig ring static mixers and three residence time units with a three-stage temperature profile allowed the synthesis of highly energetic spiro[2.4]hepta-4,6-diene in a yield of 95% with a productivity of 15 g/h under safe conditions.

ChemInform Abstract: Synthesis and Characterization of Barium Tetrafluoridobromate(III) Ba(BrF4)2.

AbstractThe title compound is synthesized by the reaction of BaF2 with liquid BrF3 under Freon‐113 (PTFE tube, 99% yield).

Continuous Heterogeneously Catalyzed Oxidation of Benzyl Alcohol Using a Tube-in-Tube Membrane Microreactor

A Teflon AF-2400 tube-in-tube microreactor is investigated for the continuous, solvent-free, catalytic oxidation of benzyl alcohol with oxygen. The semipermeable Teflon AF-2400 tube acts as the interface between the gaseous oxidant and the liquid substrate. Because of the inherent safety of this contacting method, the use of pure oxygen is possible. The semipermeable tube was packed with 1 wt % Au–Pd/TiO2 catalyst particles and placed inside a PTFE tube to provide an annular region which was pressurized with pure oxygen. This design allowed continuous penetration of oxygen through the inner tube during the reaction, resulting in higher oxygen concentration in the catalyst bed and significantly improved conversion compared to a reactor operating with an oxygen presaturated feed. The amount of oxygen available for reaction in the tube-in-tube microreactor was 2 orders of magnitude higher than that in a nonpermeable reactor with oxygen presaturated feed. The semipermeable tube reactor performance in terms of both conversion and selectivity was enhanced by increasing the gas pressure, the catalyst contact time and by dilution of the catalyst. The highest conversion of benzyl alcohol obtained for the range of conditions investigated was 44.1%, with 73.0% selectivity to benzaldehyde, at 120 °C; catalyst contact time, 115 gcat·s/galcohol; and catalyst dilution factor, 4.