Polythiophene doped with graphene oxide as in-tube solid phase microextraction phase

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  • Published: Dec 13, 2016
  • Author: Rafael Lucena
  • Channels: Gas Chromatography / Ion Chromatography / Detectors / Laboratory Informatics / HPLC / Sample Preparation / Proteomics & Genomics / Electrophoresis / MRI Spectroscopy / X-ray Spectrometry / Proteomics / Atomic / UV/Vis Spectroscopy / Infrared Spectroscopy / Raman / Base Peak / Chemometrics & Informatics / NMR Knowledge Base

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Tube solid phase microextraction (ITSPME) presents a higher efficiency than the classical SPME technique as the sample is continuously passed through the sorptive phase. Although conventional phases allow the extraction of neutral compounds, the extraction of ionic species is a little bit more complicated. Electrochemically controlled SPME, consisting on the application of an electric field during the analyte retention, makes possible these determinations. Electrochemically controlled SPME requires special coatings to be developed, where material conductivity is essential. Researchers from Tarbiat Modares University in Iran have recently proposed the use of polythiophene/graphene oxide composite in this context. The extraction, and further determination by liquid chromatography-UV detection (LC-UV), of amitriptyline and doxepin from biosamples (plasma and urine) has been used as model analytical problem.

The coating is synthesized over the inner surface of a stainless steel tube by the electropolymerization of a thiophene (monomer) solution containing graphene oxide (dopant) which is continuously recirculated using a pump. In such conditions the coating thickness can be well controlled as it is deduced from the precision of the measurements. The scanning electron microscopy pictures clearly demonstrated the effect of the inclusion of GO in the polymer structure.

Once the tube is synthesized, it is applied to the extraction of the samples. A dedicated manifold that allows the direct coupling of the extraction with the LC is also proposed by the authors. The retention of the cationic analytes over the coating requires the application of a negative potential in the tube while the elution is enhanced by the application of a positive potential. The developed extraction requires 21 min per sample and it provides, in combination with LC-UV, limits of detection as low as 0.3 µg/L with relative standard deviations better than 3.9 %.

Reference:

J. Chromat. A, 2016, 1475, 8. Yamini et al. Polythiophene/graphene oxide nanostructured electrodeposited coating for on-line electrochemically controlled in-tube solid-phase microextraction.

Blog post by: Rafael Lucena

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