## 1 Introduction  
Benzylpiperazine (BZP, **1**) is one of the dominant bioactive compounds in a relatively new class of piperazine-based illicit designer drugs in circulation [1]. This compound family includes 1-(3-4-methylenedioxypheny)piperazine (**2**), 1-(3-trifluoro-methylphenyl)piperazine (**3**), 1-(3-chlorophenyl)piperazine (**4**) and 1-(4-methoxyphenylyl)piperazine (**5**) (Figure 1). The **1**-hydrochloride salt (its most widely distributed form) is a white powder that is usually sold as tablets or capsules. It acts as a stimulant, increasing blood pressure, auditory vigilance and heart rate [2]. The biological activity of **1** is thought to be mediated through 5-HT-uptake inhibition and 5-HT1 antagonism effects [2, 3, 4, 5]. Co-administration of **1** with **3** results in psychoactive effects, including hallucinations, similar to those associated with 3,4-methylenedioxymethamphetamine (MDMA), and is 10 times more active than amphetamine [6, 7]. Ingestion of **1** can have lethal outcomes [8, 9]. Increasingly, countries have listed **1** as an illicit substance, but up until 2008, **1** was legally available to people over the age of 18 in United Kingdom and New Zealand [10, 11]. A laboratory-based analyses of **1** could easily be conducted by using spectroscopic and chromatographic techniques [12; 13], but reports on potential on-site detection have been limited to electrochemical methods [14; 15] and presumptive colour tests [12; 16]. While presumptive colour tests are rapid and cheap, these are prone to false positives, some tests are pH dependent and reagents have limited stability even with low temperature storage. Electrochemical methods rely on nonportable instrumentation with lower resolution than the chromatographic techniques. Spectroscopic on-site analysis is now possible with the emergence of portable instruments, e.g., FTIR; however, this would still require specialised training, as with all other forms of laboratory-based analytical instrumentation. Molecular imprinted polymers (MIPs) have been used by our group [17; 18] and others [19] for the capture and detection of illicit drugs. Nevertheless, there has been no report in the literature on MIPs designed for the capture of **1** to date. Thus, in this study, we aimed to develop **1**-selective MIPs, initially as an extraction and enrichment material and potentially as an on-site detection system. MIPs are generated from a functional monomer (FM), an analyte used as a template (T)-**1** in this study, a crosslinker (XL) for structural rigidity and a porogen (solvent) usually by radical polymerisation. Post-synthesis template extraction develops a complementary binding site within the polymer matrix, allowing highly selective analyte [20] or related analogue rebinding, i.e., dummy templating [21]. Due to their ease of synthesis, high stability and low cost, the use of MIPs as detection elements for several sensing platforms [22; 23; 24; 25] is gaining momentum. At their simplest, MIPs are used as highly specific solid-phase extraction systems and afford easy identification and quantification by traditional analytical means [26; 27; 28; 29; 30; 31]. Here we report on our efforts towards the development of a **1**-selective MIP via self-assembly and semi-covalent approaches. Being synthetically simpler, a majority of MIPs fall into the former classification. With self-assembly MIPs, the FM, T, XL and porogen are pre-mixed and allowed to self-associate prior to polymerisation. To optimise the formulation, pre-synthetic approaches such as virtual imprinting [32; 33; 34], semi-empirical calculations [11], thermodynamic studies [35; 36], spectroscopic (NMR [37; 38], UV-VIS [39; 40] and FTIR [41]) analyses, chemometric methods [42] and combinatorial screening [33; 43; 44] have been extensively employed. Commercially available FMs are commonly utilised, except in cases where specialty monomers are required. Covalent and semi-covalent MIPs, on the other hand, require the formation a T-FM adduct, which, at times, involves numerous synthetic steps.