The in-situ synthesis and application of nanocubic Co 3 O 4 -coated graphene oxide (Co 3 O 4 @ GO) was in- troduced for the first time to present a cost-effective, stable and convenient operation and a simple device for hollow fiber solid-phase microextraction (HF-SPME) of four selected nonsteroidal anti- inflammatory drugs (NSAIDs) including diclofenac, mefenamic acid, ibuprofen and indomethacin. The extracted analytes were desorbed by an appropriate organic solvent and analyzed via high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The prepared sorbent was approved using different characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The variables effective on the Co 3 O 4 @GO-HF-SPME method including extraction time, desorption time, desorption solvent volume, sample pH, stirring rate and ionic strength were screened via Plackett–Burman design and then optimized by Box–Behnken design. Under optimal condition, the calibration curves were linear within the range of 1.0–200.0 μg L −1 of analyte concentration with detection limits of 0.18–1.1 μg L −1 and the relative standard deviations less than 10.1%. The limits of quantification (LOQs) were in the range of 0.60–3.67 μg L −1 . Matrix effect was not observed with this method; therefore, standard addition is not necessary for quantification of target compounds. The enrichment factors were obtained in the range of 4 9–6 8. The relative recoveries of the urine sample analysis were calculated in the range of 93–102%. Finally, the presented method exhibited good sensitivity, excellent repeatability, high reusability and acceptable precision, which will be a promising method to analyze various nonsteroidal anti-inflammatory drugs in urine samples.
