Abstract
This work reports about a screening of four adsorbents with different polarity employed for the separation of the main phytocannabinoids contained in Cannabis sativa L., under normal phase liquid chromatography (NPLC). The effect of polarity and type of interaction mechanisms of the adsorbents (namely Si-, CN-, Diol-, and NH2-based SPs) on retention has been investigated under a variety of conditions either by using different combinations of apolar solvents (heptane or hexane) and alcohols (ethanol or isopropanol). The columns have also been employed for the separation of a real cannabis sample.Graphical Investigating the effect of polarity of stationary and mobile phases on retention of cannabinoids in normal phase liquid chromatography
Highlights
In the last years, there has been an increased interest around the potential of cannabis-based products for medical and nutraceutical purposes
These two cannabinoids are not directly synthesized by the plant but they are produced after exposure to heat and light of their acid precursors [1,2,3], which represent the most abundant compounds naturally occurring in Cannabis sativa L
The first part of this study focuses on the effect of the stationary phase on retention, at constant the mobile phase composition
Summary
There has been an increased interest around the potential of cannabis-based products for medical and nutraceutical purposes. The NH2 column was the most retentive for all cannabinoids, followed by Diol, CN and Si columns This retention behavior can be tentatively explained by considering the interplay of different factors including the polarity of the electron-rich functional groups present on the surface of stationary phases, the strength of the mobile phase and the characteristics of cannabinoids, in particular in relationship to their ability to behave as H bond acceptors-donors (Fig. 2). CBD and CBG seem to be most sensitive to changes in the polar modifier of the mobile phase, probably due to the presence of two hydroxy groups in their structure, while CBN, CBC and 9-THC are less affected Another interesting feature that can be evinced from these plots is that the apolar solvent (hexane or heptane), has a negliglible influence on the retention of all the cannabinoids. A possible explanation of the smaller retention observed when IPA is employed as the polar modifier could be that IPA, even though less polar than EtOH, is able to interact more strongly with polar functional groups linked through apolar propyl bridges on bonded stationary phases
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