Ultrasound-assisted emulsification microextraction combined with ultra-high performance liquid chromatography-tandem mass spectrometry for the analysis of ibuprofen and its metabolites in human urine.

In this study, a fast, simple and efficient method based on ultrasound-assisted emulsification-microextraction (USAEME) coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was successfully developed for the determination of ibuprofen (IBU) and its four metabolites (1-hydroxyibuprofen (1-HIBU), 2-hydroxyibuprofen (2-HIBU), 3-hydroxyibuprofen (3-HIBU), carboxyibuprofen (CIBU)) in human urine. For this purpose, the influence of the different parameters affecting the USAEME procedure was evaluated in order to optimize the efficiency of the process. The optimum conditions were found to be: 100μL of 1-octanol as extraction solvent, 2mL of urine sample, 15% (w/v) NaCl to control the ionic strength, ultrasonication for 10min; and centrifugation for 5min at 6500rpm. After sample preparation, chromatographic separation was achieved on a Zorbax Rapid Resolution High Definition (RRHD) SB-C18 column using the mobile phase consisting of 0.1% formic acid in water and acetonitrile in an elution gradient. Detection was performed in a triple quadrupole tandem mass spectrometer using the multiple reaction monitoring (MRM) mode and negative ionization. The proposed method showed satisfactory linearity over a wide concentration range (correlation coefficients over 0.9994). The lower limit of quantification (LLOQ) was 0.0005ng/mL for IBU and its metabolites. The intra- and inter-day precisions were in the range of 2.19-10.8% and the accuracies were between -5.93% and 6.29%. The mean recovery of analytes ranged from 90.7 to 104%. As a result, this method has been successfully applied for the sensitive determination of IBU and its metabolites in human urine samples.