40 February / March 2020
experience of the oil used had shown that only olive oil required any additional dilution procedure. We also tested an e-liquid sample at a higher concentration of CBD.
The sample was diluted in isopropyl alcohol (IPA) and methanol. The solution was filtered and further diluted with methanol to obtain a sample with a CBD concentration within the linear range.
Results and Discussion Figure 4: Resolution of 11 common cannabinoids, 10-ppm mix at 220 nm.
As simulated by the retention modelling software; baseline resolution of all 11 cannabinoids was achieved in Figure 4 with good peak asymmetry for all cannabinoids including early eluting compounds, which can be affected by strong diluent sample injections. The maximum observed back pressure was registered at 486 bar / 7,050 psi (column dependent).
As shown in Figure 5, chromatographic repeatability was demonstrated via 6 replicate injections of a 10-ppm cannabinoid mixture with a %RSD of 0.6%.
Figure 5: Six replicate injections of 10-ppm cannabinoid mixture, %RSD of 0.6%.
A 6 level linearity plot was generated for each cannabinoid standard from 0.5 ppm through to 90.9 ppm. With a 10 µL injection this means the low standard equates to only 0.005 µg of cannabinoid on column can be routinely detected, see Figure 6.
Sample analysis
A CBD Oil sample was prepared five times, employing the methodology described in the sample preparation section, to ensure both the analytical method and sample preparation were robust. The chromatogram below demonstrates the robustness of the methods.
A vape sample was then prepared following the same procedure and tested using the same analytical method, the chromatogram can be seen in Figure 8.
Figure 6: Linearity plots for CBD, CBN, Δ9-THC and Δ9-THCA, 0.5, 1, 5, 10, 50 and 90.9 ppm. Reporting
Compliant industries have seen a push towards validated computer systems over the last decade. This move towards automated processes within analytical laboratories has seen an increase in compliant laboratories dedicating time and resources to complex reports.
Figure 7: Overlay of 5 prepared CBD oil samples, CBD was found with a %RSD Rt 0.116%, Area 1.178%.
As part of this study we also worked with data to build a custom report based on two injections of the same sample at differing concentrations, the final report not only reports all relevant details, but amalgamates the two injections data. This data allows for
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