Sulfonated-doped polythiophene coatings for solid phase microextraction

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Figure 1. Structure of polythiophene
Despite their potential, the applicability of polythiophene (PT) based coatings in solid phase microextraction (SPME) is limited by their low thermal stability. In fact, PT coatings are not suitable for temperatures higher than 200 ºC and therefore they are not applicable for the extraction of a wide variety of semi-volatiles analytes. Moreover, the use of low desorption temperatures usually causes carry-over problems as the analytes are not effectively desorbed between two consecutive extractions. The improvement of the thermal stability of PT can be achieved by two different strategies which consist in the addition to the polymerization mixture of dopants with negatively charged groups. In the first approach, special reagents (like surfactants) are directly added to the polymerization mixture while in the second approach special monomers containing negative charged moieties are used to produce the so-called self-doped polymers.

The last approach, which involves a covalent bond of the negatively charged functional group to the polymer structure, has been recently employed to prepare sulfonated-polythiophene (SPT) coatings. The SPT coatings, which are obtained by an electrochemical deposition with a thickness of 25 µm, show an enhanced thermal stability (up to 350 ºC) compared to the PT-based ones. Moreover, the coatings can be reused up to 60 times with a negligible effect on their sorptive properties.

The SPT coatings have been applied for the determination of phthalate esters in water samples using a headspace-SPME procedure. The effect of all the extraction variables has been evaluated in depth and the final procedure allows the determination of the analytes by GC/FID with limits of detection lower than 0.12 ng/mL.

References

Link to the article: Preparation and evaluation of thermally stable nano-structured self-doped polythiophene coating for analysis of phthalate ester trace levels.

Link to the article: Electropolymerization of self-doped polythiophene in acetonitrile containing fluorosulfonic acid.

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