Multi-walled carbon nanotube-based dispersive solid phase extraction with following back-extraction for HPLC/UV determination of Rosmarinic acid in lemon balm and Rosemary plant samples

Abstract

In this paper, dispersive solid phase extraction with following back-extraction and HPLC/UV determination of Rosmarinic acid have been investigated. Multi-walled carbon nanotubes were used as sorbent in the suggested method. The effectiveness of some parameters such as extraction time, sorbent dosage, pH and ionic strength of the aqueous solution on Rosmarinic acid adsorption were studied. The extraction time of 5.0 min, adsorbent weight of 5.0 mg, and pH of 2.5 were obtained as the optimum experimental parameters. Adsorption of Rosmarinic acid molecules was almost independent from ionic strength. For back-extraction purpose a basic solution containing methanol was brought into contact with sorbent to desorb Rosmarinic acid molecules from sorbent containing adsorbed Rosmarinic acid molecules. Linear range of HPLC method for Rosmarinic acid quantification was 1.80–21.62 mg/L (R2 = 0.998). The relative standard deviation, limit of detection, and limit of quantification for the suggested method were 0.81%, 0.68 mg/L, and 2.86 mg/L, respectively. The proposed method was applied for extraction and HPLC/UV determination of Rosmarinic acid in Lemon balm and Rosemary plant samples. Comparison between obtained chromatograms before adsorption and after desorption processes showed that suggested extraction/back-extraction process has good selectivity and efficiency for separation of Rosmarinic acid molecules from interfering molecules existing in the plant extracts. The proposed method is efficient, low cost, fast, and simple for separation, extraction, and determination of Rosmarinic acid.