Ultrasound assisted microextraction-nano material solid phase dispersion for extraction and determination of thymol and carvacrol in pharmaceutical samples: Experimental design methodology

In the present study, for the first time, a new extraction method based on “ultrasound assisted microextraction-nanomaterial solid phase dispersion (UAME-NMSPD)” was developed to preconcentrate the low quantity of thymol and carvacrol in pharmaceutical samples prior to their HPLC-UV separation/determination. The analytes were accumulated on nickel sulfide nanomaterial loaded on activated carbon (NiS-NP-AC) that with more detail identified by XRD, FESEM and UV-vis technique. Central composite design (CCD) combined with desirability function (DF) was used to search for optimum operational conditions. Working under optimum conditions specified as: 10 min ultrasonic time, pH 3, 0.011 g of adsorbent and 600 μL extraction solvent) permit achievement of high and reasonable linear range over 0.005-2.0 μg mL−1 (r2 > 0.9993) with LOD of thymol and carvacrol as 0.23 and 0.21 μg L−1, respectively. The relative standard deviations (RSDs) were less than 4.93% (n = 3).