A fast and reliable method to quantify neral and geranial (citral) in essential oils using ¹H NMR spectroscopy

Abstract

Citral (3,7‐dimethyl‐2,6‐octadienal), a mixture of geranial and neral (two stereoisomeric monoterpene aldehydes), is considered an important raw material in the fields of fragrance, pharmaceutical, food and cosmetic industries. It is a well‐known biologically active compound present in various essential oils. A fast and reliable experimental method was developed and validated in order to quantify citral in essential oils using 1H NMR spectroscopy (experiment time at the minute level). The quantitative procedure, using anisole as internal standard, showed a perfect linearity of measurements (R2 = 0.9999), a very good accuracy (relative errors comprised between −1.9% and 0.3%) and an excellent precision (reproducibility 17.8 mg ± 1.0%). The procedure was also checked with three mixtures of weighted monoterpenes and the contents of citral, measured by GC and 1H NMR, were absolutely comparable. Then, the method was successfully applied to measure the contents of citral in 10 commercially available essential oils. Among the investigated samples, citral varied from 2.9% (Zingiber officinalis) to 90.6% (Bakhousia citriodora).