Background: Thymol and carvacrol are the most important dietary constituents in thyme
species. These two active compounds are used for the standardization of pharmaceutical compounds.
Objective: In this work, a simple and reliable ultrasonic assisted dispersive solid phase microextraction
method (USA-DSPME) coupled with high performance liquid chromatography-ultra violet detection
system was developed to determine thymol and carvacrol in pharmaceutical syrups. The efficiency of
SPME sorbent was examined through several sorbents and finally Graphene Oxide (GO) was applied
for extraction of the analytes. Method: The efficiency of GO was compared with three reduced forms of
GO adsorbents as well. Several effective factors on the extraction performance were investigated.
Results: Under the optimized conditions for the GO sorbent, inter and intra-day relative standard deviations
(RSDs, n = 3) and the Limits of Detections (LODs) were lower than 5.0% and 0.02 μg/ml, respectively.
Moreover, good linear ranges were observed in wide concentration ranges with R-squared
larger than 0.9961 for both thymol and carvacrol.
Conclusion: The present method is reliable and simple for determination of carvacrol and thymol in