## 1 Introduction  
Solid phase microextraction (SPME) is a solventless sampling and preconcentration technique that has gained popularity since its introduction by [PERSON] and co-workers in the early 1990s [1]. This technique combines the sampling, extraction, concentration, and sample introduction into the apparatus steps in a single micro device [2]. The corner stone of this device is the polymeric coating material, which allows for the sorption/desorption of the compounds of interest. Polydimethylsiloxane (PDMS), polyacrylate (PA), and divinylbenzene (DVB) [3] are the most commonly used commercially available coatings. However, and despite their many advantages, these coatings might restrict and hinder the detection and analysis of certain compounds due to their lack of specificity. To overcome this problem, a broad range of alternative phases, spanning from carbon-based nanomaterials [4],metal-organic frameworks [5], biomaterials [6], and ionic liquids [7], have been recently studied and evaluated. Ionic liquids (ILs) have emerged as promising coating materials for SPME due to their unique properties: besides their almost null vapor pressure and low flammability, the most advantageous feature of ILs is their chemical tunability [8], which can be attained through a plethora of cations and anions that can be appropriately chosen to prepare task-specific ILs. This is particularly attractive in the development of highly specific SPME fiber coatings, since the number of cation-anion combinations can be, theoretically, as high as \(10^{18}\)[9]. ILs in SPME coatings were introduced by [PERSON] et al. [10] in 2005. The authors prepared a 1-octyl-3-methylimidazolium hexafluorophosphate ([C\({}_{\text{s}}\)mim][PF\({}_{6}\)]) coating to analyze a mixture of aromatic compounds present in paints. Despite their innovative use, the proposed fiber coatings were less sensitive than the commercial ones, probably due to the small amount of IL used. Another drawback of using ILs in SPME fiber coatings is their significant decrease in viscosity with temperature, resulting in a loss of coating and a consequent need of recoating before each extraction. In this line, poly(ionic liquids) (PILs), a sub-group of polyelectrolytes [11] that combines the mechanical and thermal properties of polymers with the high tunability and versatility of ILs, have been considered as more promising alternatives in this type of analyte-selective application [12; 13; 14]. analytes such as polycyclic aromatic hydrocarbons [15], CO\({}_{2}\)[16], alcohols and amines [17; 18], and benzene derivatives among others [19; 20] have been the focus of SPME analysis using PILs coatings. The good results, both in terms of stability and performance, confirm the real advantage of using PILs as SPME coatings. However, all of these studies are restricted to imidazolium-based polycations [21], and therefore the most appealing feature of these materials, their tunability, still remains totally underexplored. Considering the increasing challenges faced by analytical chemistry in a wide range of domains, such as for example, environmental, food, and health sciences, the development of new SPME coating material clearly deserves a deeper investigation. Consequently, we here unravel the effect of changing the polycation in PILs-based SPME fibers, moving from imidazolium-based polymers to pyrrolinium-based polymers. Similarly to ionic liquids, where the choice of the cation-anion combination leads to improved performances, PILs tunability can be crucial for this type of highly specific tasks. In this work, we present the use of pyrrolinium-based PILs (Pyrr-PILs) bearing different alkyl chain lengths (C2, C8, and C14) as SPME fiber coatings. Although the excellent properties of these PILs in gas separation processes have been formerly demonstrated [22], their synthesis called upon complex high temperature processes and nasty solvents [23].