Metabolomics fingerprinting of Egyptian calendula (Calendula officinalis L.) essential oil and absolute by direct infusion into rapid evaporative ionization mass spectrometry

The present research is intended to provide a rapid and thorough method for the detection and characterization of the metabolites present in Calendula officinalis L. derived products, avoiding long analysis times and use of excessive amounts of solvents and energy, with a significant reduction of waste generation. Rapid Evaporative Ionization Mass Spectrometry (REIMS) was explored as ambient ionization source, coupled with a quadrupole-time of flight (Q-ToF) high-resolution tandem MS detector to enhance identification capability. Samples were introduced in REIMS-Q-ToF system by direct infusion excluding clean-up procedures and chromatographic separations. A characteristic fingerprint of the samples was obtained in a very short time (30–60 s). A huge number of phytochemical compounds belonging to different chemical classes was detected by matching the mass accuracy data in commercial and online database. Conventional gas and liquid chromatography analysis were also used as confirmatory methods. The adherence of the developed REIMS-Q-ToF method to green chemistry principles was quantitatively estimated and compared with conventional chromatographic techniques. For this purpose, different greenness evaluation tools (Analytical greenness metric (AGREE) and Modified Complementary Green Analytical Procedure Index (ComplexMoGAPI)) were applied along with Blue applicability grade index (BAGI) for practicality evaluation.