Measurement of low picomolar levels of triamcinolone acetonide in human bronchoalveolar lavage fluid by gas chromatography-electron-capture negative-ion mass spectrometry

The intense inherent electron-capture properties of the C21 acetate derivat ive of triamcinolone acetonide (TAA) under methane chemical ionization mass spectrometric conditions were exploited for the development of a highly se nsitive and selective gas chromatography-mass spectrometric (GC-RIS) techni que for measurement of levels of TAA in human bronchoalveolar lavage (BAL) fluid. After the addition of 3.0 ng of a heptadeuterated analog of TAA and varying concentrations of TAA to 2-ml aliquots of BAL fluid, the deuterium and protium forms of the steroid were extracted with diethyl ether, convert ed to the C21 acetate derivative, and purified via adsorptive chromatograph y prior to GC-MS analysis. Standard curves obtained from 2-ml aliquots of B AL fluid were linear over a wide range of concentrations of TAA from 0.0 to 24,600 pg/2-ml aliquots of BAC fluid. Levels as low as 6.0 pg/ml (13.8 pmo l L-1) in BAL fluid can be reliably determined in 2-ml aliquots of the biol ogical fluid with <10% error. These findings suggest that the assay method exploiting the intense electron-capture properties of TAA is highly suitabl e for determination of the deposition pattern and in vivo kinetics of TAA. in human airways following inhalation of the steroid. (C) 2001 Academic Pre ss.