A method for determination of aldosterone in adrenal tributary venous serum by derivatization using Girard P reagent isotopologues followed by LC/ESI-MS/MS

The quantification of aldosterone (ALD) in adrenal tributary venous blood serum/plasma combined with the super-selective adrenal venous sampling (ssAVS) technique is recognized as a definitive procedure for differentiation of the forms of primary aldosteronism (PA), identification of the affected segment(s) and operating decision-making. In this study, an enhanced throughput and sensitive method was developed and validated for the quantification of ALD in ssAVS serum samples by liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) combined with derivatization using the Girard P reagent (GP) isotopologues (²H₀- and ²H₅-GP). The right and left adrenal serum samples were separately pretreated and derivatized with either isotopologue. The two samples were then combined and injected together for LC/ESI-MS/MS analysis. Based on the mass differences between the isotopologues, the derivatized ALD in the two samples were quantified within a single run. This method enabled the reproducible (intra- and inter-assay relative standard deviations, 6.6% or lower) and accurate (98.2–107.0%) quantification of the serum ALD using a 25-μL sample, and the lower limit of quantification was 1.0 ng/mL. The developed method was used for the analysis of 11 pairs of ssAVS serum samples (total of 22 samples) of patients with ALD-producing adenoma and proven to have a satisfactory applicability; this method enabled the identification of the affected adrenal and the determination of the laterality of PA, and reduced the analysis time to about 2/3 compared to the previous method for 22 samples.