Solid phase extraction and quantification of diclofenac sodium in human plasma by liquid chromatography-tandem mass spectrometry

A novel liquid chromatography-tandem mass spectrometry (LC-MS-MS) method is described for the quantitative determination of diclofenac in human K2EDTA plasma in negative ion mode and validated using zidovudine as internal standard (IS). Sample preparation was accomplished by solid phase extraction technique. The eluted samples were chromatographed on Zorbax XDB phenyl column (75 × 4.6 mm, 3.5 μm) Agilent Technologies, using a mobile phase consisting of HPLC grade acetonitrile—0.2% acetic acid in HPLC water (80: 20, v/v).The injection volume was 15 μL and the total run time was 2.0 min. The method was validated over a linear concentration range of 25 to 4004 ng/mL diclofenac. The precursors to product ion transitions m/z 294.10 to 249.90 (diclofenac) and m/z 266.0 to 222.90 (zidovudine, IS) were used for quantitation. The retention times were 1.12 and 0.86 min for diclofenac and zidovudine, respectively. Validation results show that the method is selective and capable of quantifying the analyte with good precision and accuracy. The method is stable for the studied parameters. Therefore, a rapid, sensitive LC-MS-MS method for quantification of diclofenac in human plasma was developed and can be used in therapeutic drug monitoring of this drug.