Feasibility Study of a Non-Contact Differentiation of Cannabidiol Concentrations Using Interdigital Electrodes

This feasibility study presents a novel noncontact method for differentiating standard cannabidiol (CBD) concentrations using optimized interdigital electrodes. The electrode design, with a 100 mm² sensing area on a 64 mm × 77 mm FR-4 substrate, was improved through finite element analysis. Methanol-CBD solutions (25-1000 ppm) in 2 mL glass vials were analyzed using a vector network analyzer connected via a high-frequency SMA connector, focusing on scattering parameter (S-parameter) changes. The method demonstrated high effectiveness in CBD concentration differentiation, achieving a concentration resolution of 145 MHz/50 ppm based on resonant frequency shift, with an error of 0.17% of the reading, and 0.5 dB/50 ppm using S₁₁ amplitude measurement. The proposed method offers a promising, linear, and precise technique for noncontact CBD standard analysis, with potential applications in future research. In addition, impedance measurements can be applied to enhance concentration differentiation further.