Dual-mode electrochemical/colorimetric capillary-driven microfluidic device for simultaneous determination of Δ⁹-tetrahydrocannabinol and cannabidiol in cannabis flower

Abstract

Cannabis flower is well-known for its high levels of cannabidiol (CBD). However, the medical-grade cannabis flowers must meet strict standards to guarantee high CBD content and minimal to no contamination of Δ⁹-tetrahydrocannabinol (Δ⁹-THC). Given their similar redox potentials as determined by electrochemical detection, a dual readout approach becomes essential for accurately measuring the individual concentrations of Δ⁹-THC. In this work, we developed a capillary-driven microfluidic device that integrated electrochemical and colorimetric detections. The device was made from low-cost, transparent hydrophilic PET film and double-sided adhesive film with a pump-free delivery function. Once the sample solution was loaded, analysis of total Δ⁹-THC and CBD was conducted using an electrochemical technique, with a limit of detection (LOD) of 0.26 μg/mL and linear ranges of 0 – 120 μg/mL for both total Δ⁹-THC and CBD. Simultaneously, the sample solution autonomously flowed to the colorimetric zone within the transparent hydrophilic PET film, with corresponding LOD and linear ranges of 0.44 μg/mL and 0–120 μg/mL specifically for CBD. The method involved subtracting the CBD concentration obtained by colorimetry from the total Δ⁹-THC and CBD concentration obtained by electrochemical detection. Therefore, the proposed device, with its excellent analytical performance and advantageous features of affordability, simplicity, and fully portable light-controlled box, offers a practical alternative for quality control in the assessment of Δ⁹-THC and CBD levels in cannabis flowers.