Evaluating the measurement uncertainty in determination of eugenol content in cloves by gas chromatography

Cloves (Syzygium aromaticum) are valued for their high eugenol content, necessitating accurate quantification for quality control. This study determined eugenol in a commercial clove sample using Gas Chromatography with Flame Ionization Detection, employing methyl salicylate as an internal standard following the Chinese Pharmacopoeia 2015 methodology. A comprehensive evaluation of the measurement uncertainty associated with this determination was performed according to the Guide to the Expression of Uncertainty in Measurement and EURACHEM/CITAC guidelines. Major potential uncertainty sources, including the relative correction factor, peak areas (analyte and internal standard), sample volume, internal standard concentration, sample mass, and repeatability, were identified and quantified. The average eugenol content was found to be 17.91% m/m. The eugenol content met the threshold required by the Chinese Pharmacopoeia (which mandates not less than 11.0% m/m) and confirmed the suitability of the commercial product for medicinal use. The combined relative standard uncertainty was calculated as 0.199, leading to an expanded uncertainty of 7.12% (coverage factor k = 2), corresponding to an absolute uncertainty of ± 1.28% m/m eugenol content (or ± 12.8 mg/g). The primary contributors to the overall uncertainty were identified as the peak area of the internal standard and method repeatability, validating the method's reliability for quality control purposes within the established uncertainty limits.