Measuring binding and speciation of hydrophobic organic chemicals at controlled freely dissolved concentrations and without phase separation

Varvara Gouliarmou, Kilian E.C. Smith, Lis Wollesen de Jonge, Philipp Mayer

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The binding and speciation of hydrophobic organic chemicals (HOCs) in aqueous solutions were determined by controlling chemical activity and measuring total concentrations. Passive dosing was applied to control chemical activities of HOCs in aqueous solutions by equilibrium partitioning from a poly(dimethylsiloxane) polymer preloaded with the chemicals. The HOC concentrations in the equilibrated solutions [C-solution(eq)] and water [C-water(eq)] were then measured. Free fractions of the HOCs were determined as C-water(eq)/C-solution(eq), whereas enhanced capacities (E) of the solutions for HOCs were determined as C-solution(eq)/C-water(eq). A mixture of polycyclic aromatic hydrocarbons served as model analytes, while humic acid, sodium dodecyl sulfate, hydroxypropyl-beta-cyclodextrin, and NaCl served as model medium constituents. The enhanced capacities were plotted versus the concentrations of medium constituents, and simple linear regression provided precise partition ratios, salting out constants, and critical micelle concentrations. These parameters were generally in good agreement with published values obtained by solid phase microextraction and fluorescence quenching. The very good precision was indicated by the low relative standard errors for the partition ratios of 0.5-8%, equivalent to 0.002-0.03 log unit. This passive dosing approach allows binding and speciation of HOCs to be studied without any phase separation steps or mass balance assumptions.
Original languageEnglish
JournalAnalytical Chemistry
Volume84
Issue number3
Pages (from-to)1601-1608
ISSN0003-2700
DOIs
Publication statusPublished - 2012
Externally publishedYes

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