LC-determination of five paraben preservatives in saliva and toothpaste samples using UV detection and a short monolithic column

The present study reports the development and application of an HPLC–UV method for the simultaneous separation and determination of five paraben preservatives (methyl-, ethyl-, propyl-, n-butyl- and iso-butyl-paraben) in real samples. All analytes were separated efficiently in less than 20 min using a simple H₂O:ACN linear gradient and a short monolithic column (50 mm × 4.6 mm i.d.) at a flow rate of 3.0 mL min⁻¹. Phenoxyethanol was used as chromatographic internal standard. The method was validated for linearity, limits of detection and quantification, accuracy and precision. Human saliva and toothpaste samples were analyzed after SPE pretreatment on Licrolut RP-18 cartridges. The detection limits varied between 0.1 and 0.3 mg L⁻¹ in all cases and the percent recoveries between 86 and 113%.