Development of an LC-MS method for measuring TNF in human vaginal tissue

A sensitive, accurate, and precise liquid chromatography-mass spectrometry assay for the determination of tenofovir (TNF) in human vaginal tissue was developed and validated. After homogenization of the tissue, solid-phase extraction on Varian Bond Elut-C(18) column was used for sample clean up. Chromatographic separation of TNF and the internal standard (tolbutamide) was achieved with a Varian Polaris 3C(18)-A reversed-phase analytical column (150 mm x 2 mm). A gradient method using 0.1% formic acid in water and 0.1% formic acid in acetonitrile was employed. Detection of TNF and tolbutamide was achieved by electrospray ionization mass spectrometry in the positive ion mode using 288.05 and 271.00 m/z, respectively. Linear TNF calibration curves were obtained between 1-1,000 ng/mL with a correlation coefficient (r(2)) greater than 0.999. Intra- and inter-day accuracy for TNF ranged from 89.7% and 109.4% and from 97.3% and 104.9%, and precision ranged from 1.3% and 10.9% and 2.6% and 9.0%, respectively. This is the first validated method developed to quantitate TNF in human tissues.