Determination of non-steroidal anti-inflammatory drugs in urine by hollow-fiber liquid membrane-protected solid-phase microextraction based on sol–gel fiber coating

A new rapid, simple and effective cleanup procedure is demonstrated for the determination of ibuprofen, naproxen and diclofenac in urine samples by using hollow-fiber liquid membrane-protected solid-phase microextraction (HFLM-SPME) based on sol–gel technique and gas chromatography–flame ionization detector (GC–FID). In this technique, a sol–gel coated fiber was protected with a length of porous polypropylene hollow fiber membrane which was filled with water-immiscible organic phase. Subsequently the whole device was immersed into urine sample for extraction. Poly(ethylene glycol) (PEG) grafted onto multi-walled carbon nanotubes (PEG-g-MWCNTs) was used as extraction phase to prepare the sol–gel SPME fiber. Important parameters influencing the extraction efficiency such as desorption temperature and time, organic solvent, extraction temperature and time, pH, stirring speed and salt effect were investigated and optimized. Under the optimal conditions, the method detection limits (S/N = 3) were in the range of 0.03–0.07 ng mL−1 and the limits of quantification (S/N = 10) between 0.08 and 0.15 ng mL−1. Relative standard deviations for intra-day and inter-day precisions were 4.8–9.0% and 4.9–8.1%, respectively. Subsequently, the method was successfully applied to human urine fractions after administration of ibuprofen, naproxen and diclofenac.