Hydrogen peroxide is available in different purity grades depending on its use. High purity H2O2 (electronic grade) requires very low contamination levels, e.g., less than 1 μg/L of trimethylamine (TMA). This application describes the determination of trimethylamine in a high-purity H2O2 solution (30%). Analysis is performed using Inline Preconcentration with Matrix Elimination (MiPCT-ME) applying conductivity detection after sequential cation suppression.