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Cannabidiol (CBD) is a popular natural remedy used in many pharmaceutical, food, and cosmetic products. CBD is just one of over 100 chemical compounds found in the cannabis plant. Unlike tetrahydrocannabinol (THC), CBD is not psychoactive. This characteristic makes CBD an appealing option for those who are looking for relief from pain and other symptoms without the mind-altering effects associated with consuming marijuana or resin concentrates. CBD oil is made by extracting the compound from the plant, then diluting it with a carrier oil (e.g., coconut or hemp seed oil).

The standard HPLC method requires 45 minutes to perform by highly trained analysts. In contrast to the primary method, Vis-NIR spectroscopy is a cost-efficient and fast analytical solution for the determination of cannabinoid content in oils.

DS2500 Liquid Analyzer and a sample filled in a disposable vial.
Figure 1. DS2500 Liquid Analyzer and a sample filled in a disposable vial.

17 samples of three different CBD carrier oils (hemp, fish, and MCT (medium-chain triglycerides) oil) were measured in transmission mode with a DS2500 Liquid Analyzer. The built-in temperature control was set to 40 °C to acquire reproducible spectra. For convenience, disposable vials with a path length of 8 mm were used, which made cleaning of the sample vessels unnecessary. The Metrohm software package Vision Air Complete was used for all data acquisition and prediction model development.

Table 1. Hardware and software equipment overview
Equipment Metrohm number
DS2500 Liquid Analyzer 2.929.0010
DS2500 Holder 8 mm vials 6.7492.020
Disposable vials, 8 mm 6.7402.000
Vision Air 2.0 Complete 6.6072.208

All 17 measured Vis-NIR spectra (Figure 2) were used to create a prediction model for quantification of the cannabinoid content. The quality of the prediction models was evaluated using cross-validation, which display a very high correlation between Vis-NIR prediction and primary method values. The respective figures of merit (FOM) display the expected performance of a prediction during routine analysis.

Figure 2. Vis-NIR spectra of CBD oils with varying cannabinoid content measured on a DS2500 Liquid Analyzer.
Figure 3. Correlation diagram for the prediction of cannabinoid content in CBD oils using a DS2500 Liquid Analyzer.
Table 2. Figures of merit for the prediction of cannabinoid content in CBD oils using a DS2500 Liquid Analyzer.
Figures of Merit Value
R2 0.959
Standard error of calibration 0.99%
Standard error of cross-validation 1.21%

This application note demonstrates the feasibility of the DS2500 Liquid Analyzer for the determination of cannabinoid content in CBD oils. In comparison to the HPLC method (Table 3), the time to result is a major advantage of NIR spectroscopy, since a single measurement is performed within one minute.

Table 3. Time to result for the cannabinoid content determination in CBD oils using HPLC method.
Parameter Method Time to result and workflow
Cannabinoid content HPLC ∼5 min (preparation) + ∼40 min (HPLC)
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