Quantification of Carvacrol and Thymol in Herbs

Stock standard solutions of carvacrol and thymol (1000 mg L⁻¹) and I.S. (100 mg L⁻¹) were prepared in methanol. Working solutions were obtained via appropriate dilution of the stock standard solution with double distilled water. The solutions were stored in a suitable container and, then, kept at refrigerator (4 °C) in the dark place. Calibration standards were made at different concentration ranges, each one having three replicates. Furthermore, two plant materials (thymus, savory) were provided from Ilam Province, Iran. After identification, the samples were cleaned, air-dried and, finely, grounded. Subsequently, the extract was prepared via successive maceration of the powder. As follows, 5 mL of MeOH/water (80 : 20%) mixture was added to 0.2 g of samples. The mixture was sonicated for 20 min and, then, left in room temperature for 48 h. Afterwards, the mixture was centrifuged and filtered and, then, the supernatant was separated and stored at 4 °C for subsequent experiments.