Polythiophene/graphene oxide nanostructured electrodeposited coating for on-line electrochemically controlled in-tube solid-phase microextraction

- A novel polythiophene/graphene oxide (PTh/GO) nanostructured coating was introduced.
- PTh/GO was prepared on inner surface of stainless steel tube by electrochemical method.
- It was used for on-line electrochemically controlled in-tube solid phase microextraction.
- Antidepressants drugs of amitriptyline and doxepin were extracted as model analytes.
- The method was applied for analysis of the drugs in human urine and plasma samples.

In this work, a novel polythiophene/graphene oxide (PTh/GO) nanostructured coating was introduced for on-line electrochemically-controlled in-tube solid phase microextraction of amitriptyline (AMI) and doxepin (DOX) as antidepressant drugs. The PTh/GO coating was prepared on the inner surface of a stainless steel tube by a facile in-situ electro-deposition method and it was used as a working electrode for electrochemically control in-tube solid phase microextraction. In the PTh/GO coating, GO acts as an anion dopant and sorbent. The PTh/GO coating, compared to PTh and GO coatings, exhibited enhanced long lifetime, good mechanical stability and a large specific surface area. Regarding the in-tube SPME, some important factors such as the extraction and desorption voltage, extraction and desorption times and flow rates of the sample solution and eluent, which could affect the extraction and separation efficiency of the analytes, were optimized. Total analysis time of this method including the online extraction and desorption time was about 21 min for each sample. AMI and DOX were extracted, separated and determined with limits of detection as small as 0.3 μg L−1 and 0.5 μg L−1, respectively. This method showed good linearity in the range of 0.7-200 μg L−1, 2.3-200 μg L−1 and 2.9-200 μg L−1 for AMI, and in the range 0.9-200 μg L−1, 2.5-200 μg L−1 and 3.0-200 μg L−1 for DOX in water, urine and plasma samples, respectively; the coefficients of determination were also equal to or higher than 0.9976. The inter- and intra-assay precisions (RSD%, n = 3) were in the range of 2.8-3.4% and 2.9-3.9% at the three concentration levels of 5, 25 and 50 μg L−1, respectively. Finally, under the optimal conditions, the method was applied for the analysis of the drugs in human urine and plasma pretreated samples and good results were obtained.