## 2 Results and Discussion  
### Cannabinoids Content  
Current ambiguous all-purpose regulations allow huge variations in the quality and safety of the CBD-based preparations available on the market and clear labelling regarding the exact concentration of CBD is not yet mandatory. Our results demonstrate that CBD concentrations were not always in accordance with producer information (Table 1). As a matter of fact, nine out of 14 tested samples presented concentrations that differed notably from the declared amount, while the remaining five preserved CBD levels within optimal limits (the variation was less than 10%). Our analysis also revealed that two preparations (particularly oils 8 and 10) exhibited higher levels of CBD than those specified by producers, while in another two (samples Oil_3 and Oil_14) the CBD content was far inferior to the stated values. In one sample, the theoretical CBD concentration was not indicated on the label and therefore values obtained could not be compared to the producer's statement. Taken together, the results highlighted the extreme variability of the commercialised CBD oil preparations, justifying the need for stricter regulations/controls. Precise information regarding the composition of each lot that is available on the market is crucial for consumers who have to be able to properly adapt the recommended dose to the available/purchased preparation [9]. These results are in agreement with those obtained from a preliminary study toward the labeling accuracy of cannabidiol extracts preparations from products available on the US market. In the tested products, 26% contained less CBD than labeled, which could negate any potential clinical response [30]. The over labeling of CBD products in the study was similar in magnitude to levels that triggered warning letters to 14 businesses in 2015-2016 from the US Food and Drug Administration suggesting that there is a continued need for federal and state regulatory agencies to take steps to ensure label accuracy of these consumer products. Although CBD is a principal constituent of the examined cannabis oil extracts, the original plant is only capable of producing its acid form, cannabidiolic acid (CBDA). Decarboxylation of CBDA catalysed by thermal exposure during extraction conditions leads to the conversion of CBDA to the CBD as the corresponding decarboxylated (neutral) counterpart. Therefore, the determination of CBDA is important in order to evaluate the CBDA decarboxylation rate and effectiveness of the reaction during the extraction process [31]. Interestingly, looking through the web sites of the CBD oil producers enrolled in this survey, it can be found that some of them published an analytical report in which only the total CBD content as the sum of CBD + (0.877 CBDA) is reported. This is quite problematic as the biological effects of the neutral and acidic forms are remarkably different [5]. Generally, expressing the CBD content as a sum of the acidic and neutral forms is conditioned by the analytical method applied. Concretely, it occurs when gas chromatography (GC), one of the most commonly used analytical platforms for cannabinoid analysis, is used [31]. It involves the heating of the sample at high temperature in the injector prior to the chromatographic separation that leads inevitably to the decarboxylation of the cannabinoid acids. Therefore, the analytical result is the sum of the acid and neutral forms. The GC method is still officially employed by the authorities for the determination of cannabinoids, but obviously is unsuitable. A few research groups continue to suggest that an accurate cannabinoid profile should be evaluated by determining the acid and neutral forms separately [12; 31]. Results obtain in this study confirms this necessity. Employing the LC-HRMS technology, we were able to distinguish the acidic form from neutral CBD, and to examine the wide concentration range.