An Electrochemical Gas Sensor for Δ 9 -Tetrahydrocannabinol in Cannabis Smoke: A Novel Approach for Air Quality Monitoring in Legal Cannabis Consumption Areas

As cannabis legalization expands globally, detecting Δ 9 -tetrahydrocannabinol (Δ 9 -THC) in air has become crucial for public health monitoring. This research addresses a significant gap by developing the first electrochemical sensor for gas-phase Δ 9 -THC detection, effectively overcoming electrode fouling challenges commonly found in liquid-phase sensing. Our innovative approach employs a manganese dioxide-modified screen-printed graphene electrode (MnO 2 /SPGE) with a poly(acrylic acid) membrane immobilized with Fast Blue B salt. This configuration creates a selective sensing interface that facilitates both accumulation and specific interaction with Δ 9 -THC molecules. The proposed sensor demonstrated excellent analytical performance with a linear detection range of 25–250 ppb (R 2 = 0.9905), a limit of detection of 4.5 ppb, and sensitivity of 0.06 μA/ppb. Interference studies revealed exceptional selectivity, with minimal signal variations (±5%) despite high concentration ratios of potential interferents commonly found in postcannabis smoking environments. The proposed sensor’s practical applicability was validated through comparative analysis with HPLC and GC–MS, successfully detecting Δ 9 -THC in cannabis tobacco smoke while showing no response to non- Δ 9 -THC-containing cigarette samples. This low-cost, disposable sensor offers significant advantages in simplicity, portability, and accessibility compared to conventional gas chromatography–mass spectrometry techniques, making it suitable for field applications in air quality monitoring related to cannabis investigations.