TY - JOUR
T1 - Equilibrium sampling through membranes (ESTM) of acidic organic pollutants using hollow fibre modules in continuous steady-state mode
AU - Larsson, Niklas
AU - Utterback, Karl
AU - Toräng, Lars
AU - Risberg, Johan
AU - Gustafsson, Per
AU - Mayer, Philipp
AU - Jönsson, Jan Åke
PY - 2009
Y1 - 2009
N2 - Hollow fibre (HF) membrane modules were applied in continuous mode for equilibrium sampling through membranes (ESTIM) of polar organic pollutants. Phenolic compounds (chlorophenols, cresols and phenol) served as model substances and ESTM was tuned towards the measurement of freely dissolved concentrations (C(free)). HF membrane modules were constructed using thin-walled membrane, 1-m module length and low packing density in order to optimise the uptake kinetics of the analytes into the acceptor solution. Such custom made devices were tested and compared to commercially available modules. The former modules performed best for continuous ESTIM. The custom made modules provided steady-state equilibrium within 20-40 min and enrichment that was in general agreement with calculated distribution ratios between acceptor and sample. In experiments during which sample concentration was changed, acceptor response time to decreased sample concentration was around 30 min for custom built modules. In the presence of commercial humic acids, analytes showed lower steady-state enrichment, which is due to a decrease in C(free). Continuous ESTM may be automated and is suggested for use in online determination of C(free) of pollutants and studies on sorption of pollutants. Future studies should include optimisation of the membrane liquid and factors regarding the residence time of the acceptor solution in the fibre lumen. Qualitative aspects of DOM should also be included, as natural DOM can be fractionated. C(free) could be correlated to DOM properties that have previously been shown to influence sorption, such as aromaticity, carboxylic acid content and molecular size. (C) 2009 Elsevier Ltd. All rights reserved.
AB - Hollow fibre (HF) membrane modules were applied in continuous mode for equilibrium sampling through membranes (ESTIM) of polar organic pollutants. Phenolic compounds (chlorophenols, cresols and phenol) served as model substances and ESTM was tuned towards the measurement of freely dissolved concentrations (C(free)). HF membrane modules were constructed using thin-walled membrane, 1-m module length and low packing density in order to optimise the uptake kinetics of the analytes into the acceptor solution. Such custom made devices were tested and compared to commercially available modules. The former modules performed best for continuous ESTIM. The custom made modules provided steady-state equilibrium within 20-40 min and enrichment that was in general agreement with calculated distribution ratios between acceptor and sample. In experiments during which sample concentration was changed, acceptor response time to decreased sample concentration was around 30 min for custom built modules. In the presence of commercial humic acids, analytes showed lower steady-state enrichment, which is due to a decrease in C(free). Continuous ESTM may be automated and is suggested for use in online determination of C(free) of pollutants and studies on sorption of pollutants. Future studies should include optimisation of the membrane liquid and factors regarding the residence time of the acceptor solution in the fibre lumen. Qualitative aspects of DOM should also be included, as natural DOM can be fractionated. C(free) could be correlated to DOM properties that have previously been shown to influence sorption, such as aromaticity, carboxylic acid content and molecular size. (C) 2009 Elsevier Ltd. All rights reserved.
KW - Membrane extraction
KW - Equilibrium sampling
KW - Freely dissolved concentration
KW - Hollow fibre
KW - Continuous extraction
KW - Liquid chromatography
U2 - 10.1016/j.chemosphere.2009.06.010
DO - 10.1016/j.chemosphere.2009.06.010
M3 - Journal article
C2 - 19589557
SN - 0045-6535
VL - 76
SP - 1213
EP - 1220
JO - Chemosphere
JF - Chemosphere
IS - 9
ER -