## 1 Introduction  
Olive oil is a widely used food ingredient around the world. According to the International Olive Council, the global table olive production has more than tripled in the past three decades, reaching over three million tons in the 2020-2021 crop year [1; 2], with a 162% increase in consumption [1]. Despite its widespread acceptance, extra virgin olive oil (EVOO) produced in Europe, particularly in Mediterranean countries such as Spain and Italy, is considered to be of the highest quality and nutritional value. However, the table olive production of the European Union is limited, accounting for less than one-third of the world's table olive production in 2020-2021 [2]. Furthermore, European EVOOs have a higher market value, making them vulnerable to adulteration with cheaper vegetable oils such as sunflower, rapeseed, corn, or soybean oils. As a result, reliable quality assurance techniques are needed to protect consumers' interests. According to previous studies, the UV-Vis spectroscopy combined with chemometrics is one of the important techniques for the adulteration detection, authentication of the geographic location or the grade of a specific olive oil product. For instance, [PERSON] et al. quantified the level of adulteration in Spanish EVOO from their UV-Vis spectra [3; 4]. The level of adulteration was quantified using linear and nonlinear modeling based on 17 chaotic parameters calculated by UV-vis scans. Linear models with more independent variables showed better statistical results. A radial basis network model with one input node and one output neuron was used for nonlinear modeling. [PERSON] et al. established an effective detection model of Italian EVOO-vegetable oil combined with principal component analysis (PCA) and partial least-squares regression (PLSR) using UV-Vis [5]. Furthermore, subsequent studies also reported that UV-Vis spectroscopy was applied to establish EVOO adulteration models [6; 7]. The UV-Vis spectroscopy has been used to determine the geographic origin of EVOO as well [8; 9]. In these studies, UV-Vis spectroscopy and high-performance liquid chromatography with a diode array detector were used to quantify main pigments in several EVOOs and compared the advantages and disadvantages of both techniques. The methods were applied to a selection of monovarietal EVOOs produced in different geographical areas in Mediterranean countries. The differences among EVOOs produced in different geographic areas were analyzed using principal component analysis (PCA) and independent component analysis to evaluate the correlation between pigments' content such as chlorophylls and carotenoids in olive oils and experimental factors such as ripeness stage, geographic origin, and cultivars. For brevity, \"experimental factor\" is addressed as factors for all subsequent descriptions. Our previous research also demonstrated that the microtiter plate reader can be utilized as a high-throughput UV-Vis spectrometer to establish an effective differentiation model for different EVOO manufacturers [10]. The advantages of UV-Vis are two-fold: both the cost is significantly lower and the sample treatment is usually simpler compared with other methods such as chromatography, infrared, and Raman spectroscopy that require either relatively expensive instruments or complex experimental procedures. However, the UV-Vis spectroscopy also has the tradeoff of relatively low selectivity and sensitivity. Therefore, to establish an effective and robust EVOO adulteration detection model, an in-depth understanding of the characteristics of the spectroscopic fingerprints under different factors is necessary. Multi-factors can significantly impact the chemical analysis procedure, such as accuracy, sensitivity, and reproducibility. In the case of EVOO adulteration detection, factors such as origin, adulteration level, and type of the adulterant can affect the robustness of the model.