MSACL 2019 EU Abstract

Analysis of Aldosterone by LC-MS/MS: Comparison between a Conventional Electrospray Ionization Source and a New Atmospheric Pressure Ionization

Elisa Danese (1), Mairi Pucci (1), Gian Luca Salvagno (1), Francisco Ferron (2), Natalia Oxana Lupsac (2), Giulia Sartori (3), Francesca Pizzolo (3), Giuseppe Lippi (1)
(1) Clinical Biochemistry section, Department of Neurological, Biomedical and Movement Sciences, University of Verona, Italy (2) Waters S.p.a. Sesto San Giovanni, Milano, Italy (3) Internal Medicine Section, Department of Medicine, University of Verona

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Elisa Danese (Presenter) University of Verona >> POSTER (PDF)

Presenter Bio: Assistant Professor of Clinical Biochemistry, Section of Clinical Biochemistry, University of Verona, Verona, Italy
Dr. Elisa Danese was born in Verona on June the 7th,1981. She has taken a degree in Pharmaceutical Chemistry and Technology in 2005, a Specialization in Clinical Biochemistry and Laboratory Medicine in 2010 and successively a PhD degree in Medical, Clinical and Experimental Science in 2014. She currently serves as Assistant Professor of Clinical Biochemistry at the University of Verona (Italy). As regards the scientific activity, she has published more than 100 articles in peer-reviewed journals, her total Impact Factor is over 300 and the Hirsch Index (H-index) is 22. Her research activities, which integrate the clinical ones, are mainly related to tumour biology and biomarkers; diagnosis and management of disorders of haemostasis and thrombosis; epigenetics; pharmacogenetics, pharmacokinetics and pharmacodynamics; pre-analytical, analytical and post-analytical variability; sport medicine; development and validation of methods in liquid chromatography and mass spectrometry.

Relevant Financial Disclosures (within past 24 months) No relevant financial relationship(s) to disclose. Conflict mitigation NOT REQUIRED.

Background and aim. Aldosterone, a mineralcorticoid steroid hormone, plays a central role in regulation of blood pressure. The usual serum or plasma concentration is in the range of pg/mL, which makes the analysis rather challenging. Liquid chromatography and tandem mass spectrometry (LC-MS/MS) offer several advantages over conventional radioimmunoassay (RIA)-based assays in terms of both higher sensitivity and better specificity.
Objective. In this work we report early results on performance comparison between a conventional electrospray ionization (ESI) source and a new atmospheric pressure ionization source, UniSpray (US) (Waters Corp.) for LC-MS/MS analysis of aldosterone.
Methods. Sample extraction was performed on Oasis MAX µElution Plate (Waters) according to the application note of the producer. Chromatographic separation was performed on ACQUITY UPLC I-Class System, using CORTECS UPLC C18 column (Waters) followed by detection on TQS-Micro Tandem Quadrupole Mass Spectrometer. Standard solutions of aldosterone and its labeled internal standard were purchased by Cayman Chemical. The calibration curves were prepared in surrogate matrix of stripped human serum purchased by Chromsystems (range, 15-2000 pg/mL). Sixty five serum samples were analyzed in duplicated with ESI and US sources, and results were then compared with those obtained by the RIA method currently used in the local laboratory.
Results. The limit of detection (LOD) and limit of quantification (LOQ) defined as the lowest concentration generating a signal to noise ratio (S/N) >3 and >10 were 5 and 10 pg/mL respectively for both sources. Within-run coefficients of variations were <6% over a broad range of values (4 sample pools). The matrix effect, evaluated as peak area of extracted post-spiked aldosterone serum samples taken as percentage of extraction solvent samples spiked to equivalent concentrations displayed a RSD of 0.5%. The recovery percentage, expressed as ratio of [(Peak Area of Pre-Spike) / (Average Peak Area of n Post-Spikes)] x 100 was 64%. A mean increase in signal intensity of 51.5% and a mean decrease in S/N ratio of 48% was observed for US compared to ESI. Linear regression analysis between RIA and LC-MS/MS on the 65 routine samples yielded correlation coefficient of 0.84 for both ESI and US. The RIA assay displayed a mean positive proportional bias of 42% and 67% compared to the LC-MS/MS assay with US and ESI sources, respectively. Data obtained in US and ESI were perfectly correlated (r=0.998).
Conclusion. For the measurement of compounds such as aldosterone, where sensitivity is critical, the present LC–MS/MS method displayed optimal analytical performance, showing advantages of using US over ESI source in term of signal intensity. Further adjustments would be needed for improving extraction protocol efficiency.