Background: Cosmetic products are required to be safe for consumers under customary
conditions of use. Preservatives are used in cosmetics at relatively low concentrations to destroy, block,
and prevent the action of any harmful organisms by biological and chemical means. The frequency of
allergy to human skin for most preservatives has been described. For quality control of cosmetic products,
the determination of these preservatives is essential.
Methods: A simple, rapid and sensitive high-performance liquid chromatography (HPLC) method was
developed and validated for the simultaneous determination of preservatives; methylisothiazolinone
(MI), salicylic acid (SA), methylparaben (MP), ethylparaben (EP) and propylparaben (PP) in selected
cosmetic products. Each compound, together with caffeine (CA) (internal standard) was extracted from
the cosmetic matrices with 50% methanol using an ultrasonicator. Chromatography resolution of the
preservatives was performed on a Chromolith Speed Rod monolithic silica column (100 mm x 4.6 mm
i.d.) with acetonitrile, and 10 mM phosphate buffer (pH 3.0) as the mobile phase under gradient elution
conditions. The detection of all compounds was monitored with diode array detection and conducted at
Results: All preservatives were baseline separated at short run-time (< 8.0 min). The proposed method
was validated over the range of 0.3–75 µg mL-1 for MI and 0.1–50 µg mL-1 for SA, MP, EP, PP, respectively,
and no correlation coefficients lower than 0.999. The recoveries at the concentrations studied
ranged from 95.6% to 103.9% with RSDs less than 3.8%. The proposed method was validated in
compliance with ICH guidelines, in terms of accuracy, precision, limits of detection and quantitation
and other aspects of analytical validation.
Conclusion: The proposed method is a powerful alternative approach for identifying and determining
of the studied preservatives in commercial cosmetic samples. The limits of detection (LODs) and quantitation
(LOQs) at the nanogram level were far below the established restrictions in the Saudi Food and
Drug Authority Regulation, demonstrating the suitability of the proposed method for routine control.
Simple sample pretreatment with monolithic HPLC-PDA developed method produced a selective and
accurate analysis without an LC-MS/MS instrument.