A More Sensitive Spectrophotometric Method for Determination of Isoniazid in Serum or Plasma

Abstract
A sensitive spectrophotometric method is described for determining isoniazid in serum or plasma. It is extracted from biological fluids by a mixture of organic solvents and re-extracted into hydrochloric acid. In this medium, isoniazid reacts with trans-cinnamaldehyde to form a derivative absorbing maximally at 340 nm. The method is five times more sensitive than published procedures in which vanillin or piperonal is used as coupling reagent for the estimation of isoniazid.