Sensitivity of an analytical procedure towards the examined compounds constitutes a very important aspect, which is absolutely essential in the quantitation of trace compounds in the studied samples. The greater the sensitivity of an analytical method, the lower the concentration of a given compound that can be quantified. A common approach to enhancing the sensitivity of chromatographic analysis for the compound of interest is its prior derivatization, typically achieved through silylation or acylation [[1], [2], [3], [4], [5], [6], [7]]. Yet, as shown in the report concerning the analysis of cannabigerol (CBG) [8], a compound with an alkyl-diene chain and a phenolic group, a significantly greater increase of gas chromatography–mass spectrometry (GC–MS) signal for CBG can be obtained, not by its silylation/acylation, but by its transformation before analysis into its cyclic form, known as the pyranic CBG derivative. The poor response of the MS detector to CBG is primarily due to the transformation of the compound into its pyranic form, caused by the absorption of electron energy by CBG molecules in the MS ionization chamber. In consequence, a decreased number of CBG ions reach the sensor of the MS detector. CBG cyclization at the sample preparation stage eliminates CBG cyclization in the ionization chamber – i.e. eliminates the consumption of energy for creating the cyclic form of CBG. When no energy is consumed on CBG cyclization in the ionization chamber, all of it is used to ionize the cyclic CBG structure created before MS detection. Thus, the preliminary cyclization of CBG causes a nine-fold increase of its GC–MS signal – three times greater than CBG silylation/acylation. The cyclic structure (more specifically, the pyran structure) of CBG is formed in the intra-molecular reaction between the alkyl-diene chain and the phenolic group, the moieties belonging to the CBG molecule. The question arises whether the phenomenon of cyclization in the MS ionization chamber is specific to CBG or if it also occurs in other compounds that possess an alkene moiety in the ortho- position relative to the phenolic OH group. If so, does a preliminary cyclization of such compounds (e.g. during the sample preparation procedure) result in an increase of their GC–MS signal? This article addresses these questions by presenting the results of GC-MS analyses conducted on a group of eight selected ortho-allylphenols [ortho-allylphenol (o-AP), ortho-eugenol (o-Eug), 2-allyl-4-nitrophenol (4-NO2-o-AP), 2-allyl-6-nitrophenol (6-NO2-o-AP), 2-allyl-4,6-dinitrophenol (4,6-diNO2-o-AP), 2-allyl-4-chlorophenol (4-Cl-o-AP), 2-allyl-6-chlorophenol (6-Cl-o-AP) and 2-allyl-4,6-dichlorophenol (4,6-diCl-o-AP)] - for their structures see Fig S1 in supplementary materials. Within this group of compounds, the average person is most likely to encounter preparations containing o-Eug. Therefore, this o-allylphenol derivative was selected as a representative for more detailed investigation. While the quantitative determination of natural eugenols (eugenol, isoeugenol, biseugenol) in blood, food and cosmetics by GC–MS does not pose a major analytical challenge, the determination of trace amounts of their synthetic representative, o-Eug, is a serious problem because its MS signal is very low compared to that from natural eugenols. As o-Eug is often added to synthetic and natural fragrance compositions to give them a specific aromatic hint [[9], [10], [11]], more sensitive and accurate methods of eugenols quantification in bio-matrices and commercially available food products and cosmetics are constantly being developed to attain the necessary sensitivity for their detection and ensure accurate quantification. The remaining derivatives of ortho-allilophenol (4-NO2-o-AP, 6-NO2-o-AP, 4,6-diNO2-o-AP, 4-Cl-o-AP, 6-Cl-o-AP, 4,6-diCl-o-AP) used in the research, as well as o-AP itself, are less commonly found in commercially available products. They are components of plant protection formulations, and their potential use in the production of anticancer drugs and antiseptic agents is being proposed [[12], [13], [14]].