Fast chiral GC recognition of citrus essential oils evaluated with greenness metrics: is this analysis sustainable in industrial quality control?

Objective Citrus essential oils (EOs) are used in several fields around the world and require constant monitoring of their quality and authenticity to avoid risks of improper use or adulteration. Chiral analysis of these EOs is essential, not only to correlate enantiomeric distribution with organoleptic and biological properties, but also to authenticate genuine EOs and detect possible adulteration with cheaper synthetic substances or from different sources [1]. Enantioselective gas chromatography (Es-GC) wıth cyclodextrin derivatives as stationary phases is a well-established technique for chiral analysis of EOs, and has also been shown to be successfully used in fast GC mode after optimization of column dimensions and analytical conditions [2]. The use of fast GC is commonly regarded as one of the most important strategies to improve environmental performance of GC analyses, but few studies have “quantitatively” evaluated its impact in this respect. In addition, industrial quality control laboratories must not only face with increasing regulatory and public attention to environmental sustainability, but also with the multiplication of norms and quality standards requiring accurate and reliable measurements, as well as practical considerations such as productivity, cost, and simplicity of methods. This study therefore aims to: i) develop and speed up chiral recognition methods suitable for citrus essential oil authentication controls, and ii) determine, through a metric tool based on the additive RGB (Red- Blue-Green ) color model [3], whether the methods are a suitable trade-off between limited energy and chemicals’ consumption, high analytical performance, and reasonable laboratory productivity. Methods Cold-pressed essential oils of bergamot (Citrus limon (L.) Osbeck), sweet and bitter orange (Citrus × aurantium L., http://www.worldfloraonline.org) were analysed with MEGA-DEX DET-Beta capillary columns coated with 30% 2I-VIIO- ethyl-3I-VII-O-ethyl-6I-VII-O-tert-butyldimethylsilyl-β-cyclodextrin diluted in PS086 stationary phase (MEGA, Legnano, Italy). Standard methods carried out with a conventional column (25m x 0.25 mm dc x 0.25 mm df.) were translated and speeded up with columns of reduced dimensions (15m x 0.18 mm dc x 0.18mm df. and 10 m x 0.10mm dc x 0.10mm df). Data elaboration was performed by supervised and unsupervised statistical treatment and the performance of the methods was evaluated through the RGB calculation model [3]. Results: Es-GC-MS analysis of essential oils of citrus fruits allows to discriminate samples of different quality. In addition, the translation of the methods to shorter and narrower columns enables to reduce analysis time, while giving results comparable to those obtained with conventional columns. At the same time, fast GC enables a reduction in energy and gas consumption and a dramatic improvement in laboratory effectiveness. Conclusions: In a world increasingly moving towards "greenness", this study proposes an analytical approach to evaluate genuineness of citrus essential oils addressing the need to reduce the carbon footprint of analyses without altering analytical performance and increasing productivity.