Application of dispersive micro-solid phase extraction with high efficiency for determination trace amount of thymol in food and hygienic samples

In this research, dispersive micro-solid phase extraction (Dμ-SPE) method based on graphene oxide (GO) sorbent, as a green, accurate and efficient method has been applied for extraction/preconcentration and determination of thymol. At first, graphene oxide was synthesized and characterized by techniques including UV-Vis spectrophotometry, Fourier transforms (FT-IR) and X-ray diffraction (XRD). The effects of various parameters such as pH of the solution, stirring time, amount of adsorbent and the concentration of thymol by the Box–Behnken design method to determine the effective parameters and interactions and to optimize these parameters in the synthesized absorbent performance for determination of thymol was investigated. The highest absorbance of thymol in the optimal conditions; pH = 4, the initial concentration of 30 ng mL-1 of thymol, adsorbent amount of 20 mg and stirring time of 28 min was obtained. Under optimum conditions, the dynamic linear range, limit of detection (LOD) and limit of quantification (LOQ) were 15-600, 4.5 and 14.85 ng mL−1, respectively. Also, the relative standard deviation (RSD, %) of the method for 300 ng mL−1 of thymol, 4.6% (n = 5) was obtained. Finally, the proposed method was successfully applied for extraction and determination of thymol in honey and mouthwash samples.