A validated, sensitive HPLC method for the determination of trace impurities in acetaminophen drug substance

A high-performance liquid chromatography (HPLC) method has been developed and validated for the simultaneous determination of n-propionyl-p-aminophenol, 3-chloro-4-hydroxyacetanilide, 4'-hydroxyacetophenone, 4-hydroxyacetophenone oxime, 4-acetoxyacetanilide and 4'-chloroacetanilide, the main impurities in acetaminophen drug substance. The chromatographic separation was achieved on an Eclipse XDB-18 reversed-phase column using a gradient elution, being solvent A: 0.01 M phosphate buffer at pH 3.0 and solvent B: methanol. The limit of quantitation (S/N=10:1) was 0.1 microg/ml for each impurity. The coefficients of variation were less than 4% for intra-day and inter-day analyses. The individual recovery of acetaminophen spiked samples ranged from 94 to 104% and the mean recovery for each level from 99 to 103% in the 1-150 microg/ml range for all impurities. The proposed method was successfully applied to the analyses of different lots and different manufactures of acetaminophen drug substance. The proposed method can be used for the routine quality control of acetaminophen.