GC MS DETERMINATION OF PYROGALLOL AND GALLIC ACID IN BIOLOGICAL MATRICES AS DIAGNOSTIC INDICATORS OF OAK EXPOSURE/

A selective and sensitive method was developed for the quantitative de termination of pyrogallol and detection of gallic acid in biological s amples. Pyrogallol was measured as a metabolite of gallotannin in bovi ne urine and serum samples. Gallic acid was formed by hydrolysis of th e gallotannins in blue oak (Quercus douglasii) leaves, tannic acid sta ndards, and rumen contents. Acid hydrolyzed or acidified samples were extracted with 5% ethanol in ethyl acetate (v/v), followed by evaporat ion and derivatization with Deriva-sil. The trimethylsilyl derivatives were analyzed by gas chromatography/mass spectrometry using selected ion monitoring. Method detection limits for gallic acid and pyrogallol were 0.5 ppm in urine and serum samples and 5 ppm in rumen contents. The diagnostic utility of the method was tested by analyzing samples f rom heifers dosed with blue oak leaves and commercial tannic acid.