## 1 Introduction  
Industrial process monitoring and automation is an important field of applied research, which involves development and implementation of novel process analytical technologies (PAT) in a variety of industries such as food, pharmaceutical, specialty chemicals, and petroleum. Monitoring and control of processes at the industrial scale are inherently challenging due to the scale, sensitivity, and complexity of the manufacturing units. A large number of PAT instrumentation, sensors and measurement techniques [1; 2] have recently emerged such as attenuated total reflectance Fourier-transform infrared (ATR-FTIR), focused beam reflectance measurement (FBRM), Raman spectroscopy, particle vision and measurement (PVM) [3], electrical capacitance tomography [4; 5], electrical resistance tomography [6] and ultrasound tomography [7; 8]. Depending on the characteristics of the process, the properties of the liquid or solid phase, and the type of measurement technique (i.e. in situ, online, or offline), different sensor technologies are adopted. Additionally, different new data acquisition and processing methods have been developed to speed up computations or improve measuring accuracy [9], for example, parallel computing, artificial neural networks [10], and machine learning [11]. PAT is particularly important in crystallization processes for the production of value-added materials. In these processes, real-time monitoring can augment understanding of the fundamentals of the crystallization mechanisms (e.g., nucleation and growth), quantify the concentration evolution, and eventually control the crystal size distribution (CSD) [12]. Crystallization is an essential separation and purification technique in the industry that can be carried out in different ways. The main driving force of the process is the supersaturation of the solute [13,14]. In crystallization from solution, supersaturation could be generated by changing the solubility of the primary solvent through the addition of a second solvent-antisolvent. Crystallization occurs because the antisolvent reduces the solute solubility in the resulting mixed solvent. The antisolvent crystallization approach, which is usually performed in a semi-batch manner, is customary practice in pharmaceuticals, nutraceutical, and agrochemicals [15]. The antisolvent method is comparatively less energy demanding and can be carried out at ambient temperature conditions [16]. In addition, it has a more significant effect on the crystalline structure and morphology due to a profound change in solvent activity; thus, it has a potential for the production of highly purified solid materials [12]. Given the importance of antisolvent crystallization technique in industrial processes, a wide range of multidisciplinary studies have been conducted to increase the understanding of the kinetics of the process and to develop sensors and monitoring instrumentation. Ultrasonic power and offline measurements were used to control crystal size distribution during antisolvent crystallization of paracetamol [17], sodium chloride [18], and glycine [19], and combined cooling/antisolvent crystallization of acetylsalicylic acid in ethanol-water mixtures were monitored using ATR-FTIR and FBRM spectroscopy [20]. The antisolvent crystallization process of sodium benzoate was monitored with a combination of in situ FBRM and ultraviolet-visible spectroscopy sensors [21]. Amongst the many different approaches for process monitoring, electrical impedance spectroscopy (EIS) is a well-known method that has been extensively used in various manufacturing industries such as pulp and paper [22], bio-analytical applications [23, 24, 25], and food characterization [26, 27]. Impedance spectroscopic measurements can be performed quickly and are economically cheaper. Wideband impedance spectroscopic measurements can pave the way towards process evaluation in a multi-parameter acquisition system [28].