Search results for "Semipermeable membrane"
showing 10 items of 24 documents
Comparison of Three Techniques for Lipid Removal from Seal Blubber: Gel Permeation, Acid Treatment, and Dialysis with Semipermeable Membrane
2000
Abstract Harbor seal blubber samples were analyzed for PCDD/Fs and PCBs by splitting the initial extract into three aliquots and applying three different techniques for lipid removal (the first step of sample cleanup methodology for GC-HRMS analysis): gel permeation chromatography (GPC), sulfuric acid treatment, and dialysis through semipermeable membrane. Correlation coefficients of analyte concentrations obtained from three sets of replicate samples ranged from 0.965 to 0.994. In addition, a number of seal blubber samples were processed without pre-extraction using only the dialysis technique. The analyte concentrations in these samples correlated well with the analyte concentrations obta…
Lipid-Filled semipermeable membrane devices and mussels as samplers of organochlorine compounds in lake water.
1995
Semipermeable membrane sampling devices (SPMDs) and caged lake mussels (Anodonta piscinalis) were simultaneously deployed at four lake watercourse sites in Central Finland four weeks in August 1992. This study was part of the regular annual monitoring of the organochlorine compounds (OCC) in pulp-mill recipient watercourses of Finland with bivalves. Chlorohydrocarbons (CHCs), chlorophenol compounds (PCPs), chloroanisoles (PCAs) and chloroveratroles (PCVs) were analyzed from lipid extract of mussels and from the synthetic triolein lipid of the SPMDs. Hexane-diethyl ether (9:1, v/v) dialysis using polyethylene membrane was applied in dean up of the SPMD lipids and, for comparison, to six sets…
Electrochemical behaviour of Nafion®+cupromeronic phthalocyanine films
1999
Abstract The surface of indium tin oxide (ITO) and graphite+polymer composite electrodes can be modified by Nafion ® films containing a little amount of dispersed electroactive substances, such as phthalocyanines. This procedure allows electroanalytical information on the electroactive deposited substance to be obtained. The preparative methods of these type of modified electrodes are discussed from voltammetric results in this work. The proposed equivalent circuit explains the voltammetric differences between these electrodes. The Nafion ® net acts as a permeable membrane to the hydrogen ions. Besides, the presence of methylviologen within the Nafion ® film makes the electron transport thr…
Uptake rates of semipermeable membrane devices (SPMDs) for PCDDs, PCDFs and PCBs in water and sediment.
2000
Uptake rates of several PCDDs, PCDFs and PCBs were measured for semipermeable membrane devices (SPMDs) under controlled conditions in bulk water and sediment. The study was performed at 19 degrees C and 11 degrees C, and water and sediment concentrations were measured during the exposure. Linear uptake rates for specific PCDD/Fs and PCBs in 19 degrees C water varied from 34 to 111 l/m2 day and in 11 degrees C water from 8.8 to 96 l/m2 day for the whole SPMD. Uptake rates at 19 degrees C sediment ranged from 9.0 to 80 mgOC/m2 day and in 11 degrees C sediment, from 3.0 to 31, mgOC/m2 day. Partitioning of the compounds between membrane and lipid was also measured during the linear uptake phase…
Donnan equilibrium of ionic drugs in pH-dependent fixed charge membranes: theoretical modeling.
2002
Abstract We have studied theoretically the partition equilibrium of a cationic drug between an electrolyte solution and a membrane with pH-dependent fixed charges using an extended Donnan formalism. The aqueous solution within the fixed charge membrane is assumed to be in equilibrium with an external aqueous solution containing six ionic species: the cationic drug (DH + ), the salt cations (Na + and Ca 2+ ), the salt anion (Cl − ), and the hydrogen and hydroxide ions. In addition to these mobile species, the membrane solution may also contain four fixed species attached to the membrane chains: strongly acid sulfonic groups (SO 3 − ), weakly acid carboxylic groups in dissociated (COO − ) a…
Determination of volatile organic compounds in contaminated air using semipermeable membrane devices
2009
Abstract Semipermeable membrane devices (SPMDs) were evaluated as passive samplers for the determination of 26 volatile organic compounds (VOCs) in contaminated air of occupational environments. A direct methodology based on the use of head-space-gas chromatography–mass spectrometry (HS-GC–MS) was developed for VOCs determinations in SPMDs, without any sample pre-treatment and avoiding the use of solvents. A desorption temperature of 150 °C for 10 min was sufficient for a sensitive VOCs determination providing limits of detection in the range of 15 ng SPMD−1 for 21 of 26 studied compounds. Linear and equilibrium uptake models were established for each VOC from compound isotherms. Highly vol…
Membranes Directly Prepared from Solutions of Unsubstituted Cellulose
2005
Summary: Starting from 5 wt.-% solutions of a prehydrolysis kraft pulp ( = 135 kg · mol−1) in the mixed solvent (dimethylacetamide + 7 wt.-% LiCl) we have prepared cellulose membranes on different supports according to the phase inversion process using above all acetone (AC) and 2-propanol as precipitants. In this context we have studied the phase behavior of the quasiternary system (DMAc+LiCl)/AC/cellulose. The obtained membranes are mechanically stable and in their mechanical and separation properties on the whole comparable to membranes consisting of regenerated cellulose. With respect to gas separation the ideal selectivity of CO2 in combination with N2 and O2 turns out to be opposite f…
Fluorenylmethoxycarbonyl-N-methylamino Acids Synthesized in a Flow Tube-in-Tube Reactor with a Liquid-Liquid Semipermeable Membrane
2013
Both steps of the N-methylation of 9-fluorenylmethoxycarbonyl (Fmoc) amino acids were carried out in a microstructured tube-in-tube reactor equipped with a semipermeable Teflon® AF 2400 membrane as the inner tubing. In the first step, gaseous formaldehyde was passed through the inner membrane to effect the acid-catalyzed conversion of the Fmoc amino acids into the corresponding N-Fmoc oxazolidinones. In the second step, liquid–liquid transfer of trifluoroacetic acid was used for the first time in such a reactor for the reductive opening of these oxazolidinones to give Fmoc N-methylamino acids in high yields.
Lipid-containing semipermeable membrane devices (SPMDs) as concentrators of toxic chemicals in the lower Fraser River, Vancouver, British Columbia.
1998
Abstract Semipermeable membrane devices (SPMDs) were deployed in the water column and in the sediments of the Lower Fraser River (B.C., Canada) to compare the levels and the congener profiles of polychlorinated dibenzo- p -dioxins (PCDDs), dibenzofurans (PCDFs) and non- ortho -chlorinated biphenyls (N-o,o′-PCBs) against those sampled by an Infiltrex resin column water sampler. Also the relationship between what was present in the ecosystem as sampled by SPMDs and what was accumulated in the tissue of resident benthic-feeding fish was explored. Only the lipid portion of the SPMDs was prepared for analysis, due to some technical difficulties in cleaning the polyethene tubing. The calculated w…
Semipermeable membrane to retain platinum atoms in the electrodeposition process of alpha spectrometry sources
1998
Abstract In earlier work alpha sources electrodeposited on stainless steel backings were analyzed by X-ray fluorescence (XRF) and Rutherford backscattering spectrometry (RBS) finding that during the electrodeposition process large quantities of platinum from the anode were deposited on the cathode surface jointly with the actinides. In the present work, a method to retain platinum atoms using an electrodeposition cell with a semipermeable membrane located between anode and cathode is proposed and tested. The XRF and RBS of alpha sources electrodeposited using this method show that there is less platinum on the stainless steel backing, thereby improving the quality of sources to be measured …