## 1 Introduction  
The development of effective and rapid techniques for preconcentration, isolation, and detection of target compounds is of great importance in the field of analytical chemistry [1]. The solid-phase microextraction (SPME) technique coupled with GC-MS fits this criterion. Functionally, SPME relies on the principles of sorption and desorption, where a target compound binds to an SPME apparatus (typically a polymeric sorptive fiber), which can be subsequently injected into a GC-MS or HPLC instrument for analysis [1, 2]. SPME has a wide scope of analytical uses, including urine and blood analysis [3], pollutant monitoring [4], and food quality assurance [5]. A wide variety of sorptive substrate materials may be used for SPME fabrication, such as polydimethylsiloxane (PDMS) [1, 6], carbon nanotubes (CNT) [7], conductive polymers [8, 9], molecularly imprinted polymers (MIPs) [10], and metal-organic frameworks [11]. Different materials can be especially advantageous, for instance, CNT are mechanically durable and have a high surface area for enhanced compound sorption [2]. Conductive polymers, such as polypyrrole, have an affinity for the sorption of charged analytes, where desorption can be controlled by an applied voltage [12]. Additionally, the chemical structure of certain conductive polymers may lend well for sorption of polar and conjugated compounds alike [9].  
Electrochemical sensors are advantageous for chemical analysis due to their rapid response times and portability. In contrast, chromatographic techniques are lab-localized and suffer from slow analysis times. Due to their electrocatalytic activity and conductivity, CNTs are favorable for use in electrochemical sensing [13]. CNT-based electrochemical sensors can measure a wide range of electroactive analytes, including, but not limited to, microbes [14], pesticides [15], hormones [16], and antioxidants [17]. Similarly, polyaniline (PANI), a conductive polymer, has several advantages, thus making it useful for incorporation into electrochemical sensing devices such as inherent electrical conductivity and stability [18]. Structurally, PANI can exist in several oxidation states, including oxidized (pernigraniline), partially oxidized (emeraldine and nigraniline), and reduced forms (leucoemeraldine) [19]. The scope of application of PANI-based electrodes is wide, with literature examples including detection of glucose [20], lactate/pH [21], hydrogen peroxide [22], and heavy metal [23]. Due to their applications in both SPME and electrochemical sensing, CNT- or PANI-based SPME fibers may allow for simultaneous electrochemical and SPME-coupled GC-MS, thereby extending their scope of analytical applications. This integrated approach provides a unique synergy with an electrochemical detection ideal for rapid chemical screening, while GC-MS is useful for qualitative and confirmative analytics.  
SPME remains a viable technique for diverse analytes extraction. Improvements in SPME tailorable materials chemistry is necessary to extend the scope of their applications. However, the high cost (\(\sim\)$250) per fiber [24] and fragility of commercial SPME fibers remains a significant disadvantage. In this work, we demonstrate a frugal and mechanically robust PANI@CNT/CNC SPME microneedle (MN) useful for electrochemical detection and for coupling to GC-MS, yielding a platform for dual complementary chemical analysis.  
The SPME stainless steel MN were fabricated via layer-by-layer (LbL) in-tube coating and were used in either electrochemical and/or SPME-coupled GC-MS analysis of different organic compounds in coffee, tea, and fruit samples. The use of the PANI@CNT/CNC SPME MN for dual electrochemical and SPME-coupled GC-MS was demonstrated using kiwi fruit, where in situ semi-quantitative antioxidant determination and organic composition analysis at different fruit sample penetration depths were performed. Figure 1 depicts a schematic for the dual SPME sensor platform for electrochemical and GC-MS detection.