Search results for "Semipermeable membrane"

Passive Air Sampling

2016

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…

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…

Convective electrodiffusion processes through graft-modified charged porous membranes

1999

Convective diffusion and electrophoresis across a charged porous membrane showing variable permeability properties were studied. The membrane used was prepared by grafting poly(acrylic acid) (PAA) onto a porous polyvinylidene fluoride (PVDF) membrane. The degree of grafting was selected to be relatively low, 18 wt%, to compromise between the ion selectivity and hydraulic permeability of the membrane. The possible electric field induced effects on the membrane permselectivity were examined after the membrane had been characterized by convective diffusion and concentration cell potential measurements. The measured electrophoresis data, however, could be modelled using the extended Teorell–Mey…

Use of semipermeable membrane devices for assessment of air quality in Tangier (Morocco)

2009

Semipermeable membrane devices (SPMDs) have been used for the evaluation of the contamination of air in both the urban and the industrial area in Tangier (Morocco). Benzene, toluene, ethylbenzene a...

Assessing air quality inside vehicles and at filling stations by monitoring benzene, toluene, ethylbenzene and xylenes with the use of semipermeable …

2007

BTEX (benzene, toluene, ethylbenzene, and xylenes) were used as target molecules to evaluate the quality of air inside motor vehicles and near filling stations, using semipermeable membrane devices (SPMDs) as low-cost passive sampling devices. A direct, fast, simple methodology based on the use of headspace-gas chromatography-mass spectrometry detection (HS-GC-MS) was developed for BTEX determinations, without any sample pre-treatment. SPMDs (25.4 cm2 surface, filled with 100 microL triolein) were employed as static samplers. After the selected deployment time, the SPMDs were heated inside a HS vial at 150 degrees C for 20 min and BTEX compounds were determined by GC-MS in selected ion moni…

Microwave-assisted extraction of polybrominated diphenyl ethers and polychlorinated naphthalenes concentrated on semipermeable membrane devices

2006

Abstract Microwave-assisted extraction (MAE) has been evaluated as an alternative to dialysis for the extraction of polybrominated diphenyl ethers (PBDEs) and polychlorinated naphthalenes (PCNs) sampled by semipermeable membrane devices (SPMDs), using gas chromatography coupled to tandem mass spectrometry (GC–MS–MS). For MAE optimization a two level full factorial design 2 3 , plus a centre point, which involves 11 randomized runs was used. The results showed that the temperature had a significant influence on the extraction of the nine PBDEs and four PCNs tested. Also, the solvent volume had a positive influence on the extraction of PBDEs and PCNs, but only in latter compounds, it achieves…

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…

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…