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Equilibrium sampling through membranes of freely dissolved chlorophenols in water samples with hollow fiber supported liquid membrane

In English

Författare

Summary, in English

The freely dissolved concentration (C-free) of pollutants is generally believed to be bioavailable and thus responsible for toxic effects. The C-free of organic weak acids and bases consists of a dissociated and a nondissociated fraction. By using chlorophenols as model compounds, a negligible-depletion extraction technique, equilibrium sampling through membranes (ESTM), was developed for the measurement of the nondissociated part of the C-free. Polypropylene hollow fiber membranes (280-mu m i.d., 50-mu m wall thickness, 0.1-mu m pore size, 15-cm length) were impregnated with undecane in the pores in the fiber wall as liquid membrane and filled with buffer solution in the lumen as acceptor. Then, the hollow fiber membranes were placed into the sample (donor) for an equilibrium extraction after sealing the two ends. The chlorophenol concentrations in the acceptor were then determined by direct injection into a HPLC system. Finally, the C-free Of the nondissociated and the dissociated species of a chlorophenol were calculated based on its measured concentration in the acceptor, its pK(a) value, and the measured pH in sample and acceptor. Theoretically calculated distribution coefficients (D = 8-970) agree well with the experimental enrichment factors (E-e(max) = 6-1124), and the equilibration time was observed to increase with increasing distribution coefficients (hours to days). The freely dissolved concentration of five chlorophenols, with a wide range of pKa (4.9-9.2) and log K-OW (2.35-5.24), were successfully determined in model solutions of humic acids and at low-ppb levels in river and leachate water.

Publiceringsår

2005

Språk

Engelska

Sidor

4800-4809

Publikation/Tidskrift/Serie

Analytical Chemistry

Volym

77

Issue

15

Dokumenttyp

Artikel i tidskrift

Förlag

The American Chemical Society (ACS)

Ämne

  • Analytical Chemistry

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1520-6882