Approach for simultaneous cannabidiol isolation and pesticide removal from hemp extracts with liquid-liquid chromatography

In this work, a computer-aided approach for selecting biphasic solvent systems for simultaneous cannabidiol (CBD) isolation and pesticide removal from hemp extracts with liquid-liquid chromatography (LLC) was investigated. By taking advantage of a fully predictive thermodynamic model (COSMO-RS), a considerable number of ternary solvent systems were screened and potential systems were identified with practically no experimental effort; the partition coefficient of the target component CBD was used as screening parameter. After the experimental validation, three solvent systems were chosen: solvent system I: n-heptane/methanol/water 4/3/1 v/v/v, solvent system II: n-heptane/acetone/water 2/5/1 v/v/v and solvent system III: n-heptane/acetonitrile/water 5/3/2 v/v/v. The 59 pesticides regulated by the state of Oregon in cannabis products were included in the next step with the aim to propose a classification system of the most critical pesticides for obtaining pesticide-free CBD. Based on CBD/pesticide separation factors (α_CBD/PEST), four critical levels were defined. Depending on the solvent system, it was shown that 50–70 % of the Oregon-listed pesticides were found to be non-critical (α_CBD/PEST > 4), while only 13–22 % were retrieved as highly and medium critical (α_CBD/PEST < 2). Using the acquired knowledge, a guideline for the selection of the best solvent system candidate for the simultaneous LLC separation of CBD and removal of Oregon-listed pesticides from hemp extracts was proposed. Following a series of LLC experiments with a pesticide-spiked hemp extract, it was shown that the pesticide classification lists can be used to select the most promising solvent system to achieve the removal of most of the contaminating pesticides.