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 (HNMR)-H-1 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.