Essential oils are appreciated worldwide for their pleasant aroma, in addition to their therapeutic, pharmacological, and cosmetic functions. For these reasons, adulteration is a common practice that decreases product quality causing economic and health issues. In this study, we present for the first time the application of a simple, inexpensive and disposable paper-based optoelectronic nose (i.e. colorimetric sensor array) to (i) discriminate sixteen different types of essential oils and (ii) detect adulterated samples. The colorimetric array was prepared by adding 1.5 μL of 9 chemo-responsive dyes with different chemical properties to each circular spot of the paper-based device. 1 mL of each essential oil was transferred to a flask and bubbled with synthetic air at an airflow of 200 mL min⁻¹. Then, the optoelectronic nose was exposed to the airstream containing the volatiles from the sample for 5 minutes. Digital images from before and after exposure were obtained using a smartphone and the RGB values were extracted using appropriate software. The color changes provided a unique color map fingerprint for each essential oil. Hierarchical clustering analysis (HCA) and principal component analysis (PCA) were successfully employed using a customized smartphone app, showing suitable discrimination of all studied essential oils as well as among adulterated and non-adulterated samples. The proof-of-concept showed the potential of the optoelectronic nose approach for the discrimination of different essential oils and the identification of adulterated samples, providing a valuable tool for quality control procedures.

中文翻译：

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纸基光电鼻的设计和应用，用于使用化学计量学网络应用程序现场辨别精油

精油除了具有治疗、药理和美容功能外，还因其令人愉悦的香气而受到全世界的赞赏。由于这些原因，掺假是一种常见的做法，会降低产品质量，从而导致经济和健康问题。在这项研究中，我们首次提出应用简单、廉价且一次性的纸基光电鼻（即比色传感器阵列）来（i）区分十六种不同类型的精油和（ii）检测掺假样品。通过向纸基装置的每个圆形点添加 1.5 μL 9 种具有不同化学性质的化学响应染料来制备比色阵列。^{将1 mL每种精油转移至烧瓶中并用合成空气以200 mL min -1}的气流鼓泡。然后，将光电鼻暴露在含有样品挥发物的气流中5分钟。使用智能手机获得曝光前后的数字图像，并使用适当的软件提取 RGB 值。颜色变化为每种精油提供了独特的颜色图指纹。使用定制的智能手机应用程序成功地采用了层次聚类分析（HCA）和主成分分析（PCA），显示出对所有研究的精油以及掺假和非掺假样品的适当区分。概念验证显示了光电鼻方法在区分不同精油和识别掺假样品方面的潜力，为质量控制程序提供了宝贵的工具。