A Look at a New Packed In-Tube Solid Phase Extraction Method
New technological developments are constantly shaping the world of medical and biological advancements. In the realm of cannabis extraction, these advancements can lead to exciting new possibilities in the administration and effectiveness of the plant for various applications. A new process developed by using a novel packed in-tube solid-phase extraction method to determine different levels of ∆ 9-tetrahydrocannabinol (THC) in varying stages of plant development and in biological fluids holds exciting promise.
Researchers have created this new extraction technique by utilizing synthesized nanoparticles dry-packed into a stainless-steel cartridge.  These particles were synthesized by using a copper/cobalt/chromium layered double hydroxide to create a plate-like nano-sorbent. The researchers used ultrasonic extraction to pull THC from plant leaves. After preconcentration, which reduced background/matrix effects that could obscure the THC, samples from different life cycle stages of the cannabis plant were run through this packed in-tube technology. The authors also analyzed THC extracted from human serum and plasma samples.
Overall, five independent variables, including the pH of the sample solution, extraction time and flow rate, and desorption time and flow rate were evaluated. Extractions times varied from 5 to 30 minutes, with 20 minutes proving to be optimal. The ideal pH for the best extraction efficiency was measured to be 10.0. At this basic pH, THC is deprotonated (loses a hydrogen), producing the anion (negatively charged ion). The THC concentrations were quantified using liquid chromatography.
Initial results using this method are intriguing. The sorbent displayed chemical stability, high anion exchange, and a long shelf-life. The in-tube extraction method demonstrated linearity for THC amounts ranging from 0.09-500 µg L-1, 0.3-500 µg L-1 and 0.4-500 µg L-1 with coefficients of determination (R2) of 0.9999, 0.9991 and 0.9994 in water, serum, and plasma samples, respectively. Limits of detection were recorded between 0.02-0.1 µg L-1.
These results highlight this method’s ability to effectively extract and quickly analyze trace amounts of THC from plant matter and biological fluids. The authors point out that the method is simpler, less expensive, “greener”, and less wasteful than conventional techniques. This holds promise in regards to phytochemical composition for cultivators as well as pharmacodynamic studies into the effectiveness and absorption of THC in the human system.
The technology used in this method was expanded from the in-tube solid-phase microextraction technique first developed in the late 1990s as a fast, inexpensive, and solvent-free style of extraction. The older extraction method often displayed low stability and long extraction times, however, and the newer layered double hydroxide style of extraction may remedy those problems. 
This new development into an existing, technology might very well lead the way for fast, efficient, and effective THC extraction and analysis. Assessing different levels of THC in varying developmental stages of the cannabis plant life cycle could also lead to new uses and applications of the plant.
- Asiabi H., et al. “Developing a Novel Packed In-Tube Solid-Phase Extraction Method for Determination ∆ 9-Tetrahydrocannabinol in Biological Samples and Cannabis Leaves.” J Sep Sci, preprint, 2019. Journal Impact Factor = 2.516