GLC determination of gamma-hydroxyphenylbutazone in plasma

A recently described GLC method for the determination of phenylbutazone and its major metabolite, oxyphenbuta- zone [1 -phenyl-2- (p -hydroxyphenyl) -3,5-dioxo-4-n -butylpyrazoli- dine], in plasma was extended to the estimation of the second major metabolite, γ-hydroxyphenylbutazone [l,2-diphenyl-3,5-dioxo-4-(3-hydroxybutyl)pyrazolidine]. The method is sensitive to 1.0 μg/ml.