## 1 Introduction  
During the last two decades, chemical analysis strategies were directed toward green chemistry norms, and consequently, solvent-free sampling methods have been placed at the center of attention [1]. As a result, the development of green and sustainable analysis procedures is currently an interesting multidisciplinary topic in a broad spectrum of sciences, including chemical analysis, environmental monitoring, biochemistry and medicinal chemistry [2]. Following these principals, one of the most important steps in analytical scale separation has been taken by introducing solid-phase microextraction (SPME), as a fast, solvent-free, easy-to-operate and efficient sampling strategy. In SPME, the separation and preconcentration processes have been merged into one step [3]. It reduces the expenses, waste, steps and time of analyses and can be easily automated and used for in vitro/in vivo biological monitoring studies [4]. SPME is coupleable with the most commonly-used chromatographic techniques such as gas chromatography (GC), high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) [5]. It can be applied in three sampling modes including direct-immersion (DI-SPME), headspace (HS-SPME) and membrane-protected SPME (MP-SPME) [6]. Different variables that affect analyte uptake, in SPME studies, such as sampling mode, the coating's chemistry, sample matrix complexity and the physicochemical properties of analytes, should be considered [7]. Headspace is the most used mode of SPME, which extracts analytes from the headspace of the sample, without contact with the sample matrix [8]. Nonetheless, it is only applicable for volatile and semi-volatile analytes [9]. On the other hand, in HS mode, fiber coating saturation occurrence is more pronounced due to its mass transfer mechanism. On the contrary, DI mode minimizes this phenomenon and provides an improved extraction for polar species, proving its priority for biochemical and in vivo studies [10]. This is important for polar analytes, which possess low volatility and are extremely soluble in aqueous matrices [11]. Among the different strategies that have been proposed to improve the efficiency of DI-SPME, electrochemically-enhanced or electroenhanced SPME (EE-SPME) [12] is the most efficacious approach. In this method, the utilization of the electrical potential of the SPME fiber increases the migration of polar analytes toward the fiber surface. For this reason, EE-SPME not only remarkably enhances the extraction efficiency, but also improves the selectivity of separation [13]. In this sampling mode, the fiber coating is directly contacted with the sample matrix. Therefore, in addition to the general variables, sample solution conditions including sample pH and ionic strength should be controlled more carefully [14]. The most used commercial SPME fibers are polydimethylsiloxane (PDMS), polyacrylate (PA), carboxan (CW), carboxan/polydimethylsiloxane (CAR/PDMS), polydimethylsiloxane/divinylbenzene, (PDMS/DVB), carboxan/divinylbenzene (CAR/DVB) and divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) [15]. Nevertheless, the commercial fibers have some drawbacks such as fragility, low capacity and high cost [16]. To overcome these limitations, use of handmade SPME fibers has become widespread in recent years. In this way, different nanomaterial solvents have been successfully used, alone or as composites [17]. These sorbents mostly have higher efficiency, compatibility, durability and lower cost in comparison with the commercial fibers [5]. In addition, very few commercial coatings are appropriate for sampling of highly polar and ionic analytes. One of the best choices to address this issue is the use of conductive polymers, especially their nanostructures [18]. Polypyrrole (PPy) is among the most popular conductive polymers for this purpose, which commonly is coated on the substrates using the electrophoretic deposition (EPD) method [19].