Absolute content determination by quantitative NMR (qNMR) spectroscopy: a curious case of aldosterone

Quantitative NMR spectroscopy has been utilized to calculate the absolute content (g g−1) of aldosterone, which is necessary for electrolyte balance and blood pressure regulation, in commercially available materials. Explanations have been provided for many signals observed in the 1HNMR spectrum, false interpretation of which can have significant effects if such a value is utilized for the primary calibrators in ID-LC-MS/MS (‘gold standard’) reference methods in clinical chemistry.