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Highlights: [•] Implementation of organic solvent gradients in micellar liquid chromatography, MLC. [•] Screening of β-blockers in urine samples with direct injection in gradient MLC. [•] 1-Propanol gradients allows the elution of β-blockers of diverse polarity. [•] Gradient elution starting with pure micellar solution benefits direct injection. [•] Optimisation of organic solvent gradients in MLC can be performed with DryLab®. [ABSTRACT FROM AUTHOR]

An HPLC-UV method to determine compounds having a hydroxyl functional group in plant essential oils is developed. The sample is diluted with 1,4-dioxane and the analytes are derivatized with phthalic anhydride. The derivatives (phthalates hemiesters) are separated on a C8 column using an acetonitrile (ACN)/water gradient. Separation conditions were optimized using the DryLab(®) method development software. For the alcohols and phenols present in mint and rose essential oils, optimization led to a ca. 40min gradient time and a column temperature of 8°C. The alcohol and its derivatives were identified using HPLC with mass spectrometry (MS) detection. A large sensitivity enhancement was obtained by derivatization protocol. The HPLC-UV method was compared to GC with flame ionization detector (FID) and GC-MS. The limits of detection (LODs) obtained by the proposed method were better than those obtained by GC-FID and of the same order as those achieved by GC-MS. The three methods were satisfactorily applied to the determination of alcohols in essential oils. Therefore, the recommended method is of interest as an alternative to GC methods, to investigate the presence of compounds having an alcohol group at low concentrations in essential oils., (Copyright © 2013 Elsevier B.V. All rights reserved.)