Solid-Phase Extraction for Photometric Determination of Rosmarinic Acid in Lemon Balm (Melissa Officinalis) Extracts

The aim of this study was evaluation of the solid-phase extraction for elimination of interference compounds from lemon balm extracts aimed for photometric determination of rosmarinic acid. In experiments, evaluated conditions were as follows: composition and volume of mobile phase, ratio between volume of sample and mass of stationary phase and flow rate of mobile phase during separation. The results indicated that interfered compounds were eliminated. The lemon balm extracts should be pretreated by adsorption on normal stationary phase (silica gel) in ratio sample volume to silica gel weight 1:1 (v/w) elution by mobile phase - diethyl ether: acetic acid (9:1; v/v) - volume - 40 times of crude extract volume - with flow rate 5 ml/min. After selection of SPE conditions, the method was validated with comparison to HPLC analysis. The results suggest that this method may be useable for determination of rosmarinic acid by photometric measurement based on the complexation of Fe2+ ions with rosmarinic acid.