AbstractTwo commonly used PMR internal reference compounds, 3‐(trimethyl silyl) propane sulfonic acid sodium salt (DSS) and 3‐(trimethyl silyl) sodium propionate (TSP), have been shown to interact with purine in aqueous solution, causing significant shifts in the resonance position of their reference protons. Tetramethyl ammonium chloride (TMACl) appears to be a more suitable reference compound for such stud