Colorimetric determination of acetaminophen

A colorimetric procedure for the emergency determination of acetaminophen in plasma is described. Acetaminophen is extracted into ethyl acetate at physiological pH to eliminate salicylate, amino acids and other polar compounds. The extract is treated with Fuller's earth to remove bilirubin and with anhydrous sodium sulphate to remove traces of aqueous droplets containing proteins or uric acid. The extract is back-extracted into carbonate and simultaneously treated with Folin--Ciocalteau reagent to produce a stable colour complex.