Solid-phase microextraction to determine micropollutant–macromolecule partition coefficients

Abstract

Aqueous micropollutants such as estradiol can have a large environmental impact-even at low concentrations. Part of understanding this impact involves determining the extent to which the micropollutants interact with macromolecules in water. In environmental samples, relevant macromolecules to which micropollutants bind are referred to as dissolved organic matter, and the most common examples of these in freshwater and coastal seawater are fulvic and humic acids. In living organisms, the most common macromolecules that affect bioavailability of a drug (or toxin) are proteins such as albumin. Using [2, 4, 6, 7 - (3)H]estradiol as an example compound, this protocol uses solid-phase microextraction and scintillation detection as analytical tools to quantify the amount of radiolabeled micropollutant available in solution. The measured free concentration after exposure to various concentrations of macromolecule (dissolved organic matter or protein) or micropollutant is used to determine the partition coefficient in the case of micropollutant-macromolecule interactions. The calibration and preparatory studies take at least 8 d, and the steps to determine the partition coefficient can be completed within 3 d. The protocol could be modified such that nonlabeled compounds are studied; instead of detection of activity by a liquid scintillation counter (LSC), the compounds can be quantified using gas chromatography-mass spectrometry (GC-MS) or liquid chromatography (LC)-MS(/MS).

Microheterogeneous Distribution of Hydroxyl Radicals in Illuminated Dissolved Organic Matter Solutions

“…K CDOM CP (L kg C –1 ) is the CDOM-water partitioning coefficient for CPs and was determined through a nd-SPME method; the results are included in Table . The fraction of CPs bound to DOM ( f CDOM ) is modeled by eq . the fraction of non-bound CPs, named aqueous CPs, is …”

“…The K CDOM values of various CPs in SRNOM solutions were determined by using a negligible depletion solid-phase microextraction (nd-SPME) method described in refs and . In detail, CP stock solutions were prepared by dissolving predetermined amounts of CPs in methanol.…”

Volatile Organic Compounds, Spectral Characterization and Morphology of Ammonium Nitrate Fuel Oil (ANFO) Samples

“…While adsorption occurs with PA fibers, absorption occurs with DVB/CAR/PDMS fibers 16. Although the extraction through the absorption process seems to be more efficient, giving to the PA fiber a greater extraction value, the fiber composed by three polymeric materials, DVB/CAR/PDMS, has less deviation, less %RSD, and possibly a wider range of chemical structures to extract, thanks to its chemical composition 17. Taking into account this, it was decided to choose the DVB/CAR/PDMS fiber to continue with the optimization of parameters, as well as the validation of the methodology.…”

Effect of Binding Components in Complex Sample Matrices on Recovery in Direct Immersion Solid-Phase Microextraction: Friends or Foe?

“…In reality, many target analytes show a preference toward binding with species present in complex sample matrices. While many applications of SPME, such as negligible depletion SPME, have as a goal the nondisturbance of bound analytes present in the sample, 24 in some applications, such as bioanalysis and food applications, some of these bound analytes can be dissociated from the matrix−analyte complex due to the employment of limited sample volumes as well as high affinity coating chemistries. In such cases, the binding equilibrium (shown in Figure S1) shifts left, facilitating the extraction of larger amounts of free-form analytes by the coating, resulting in a clean "via free form" extraction process.…”