A LC–MS/MS method for the simultaneous determination of 6‐cyanodopamine, 6‐nitrodopamine, 6‐nitrodopa, 6‐nitroadrenaline and 6‐bromodopamine in human plasma and its clinical application in patients with chronic kidney disease

The aim of this study was to develop a high‐performance liquid chromatography–tandem mass spectrometry method for the determination of 6‐cyanodopamine, 6‐nitrodopamine, 6‐nitrodopa, 6‐nitroadrenaline and 6‐bromodopamine in human plasma samples. Strata‐X 33 μm solid‐phase extraction cartridges were used for the extraction of the catecholamines from human plasma samples. The catecholamines were separated in a 150 × 3 mm Shim‐pack GIST C18‐AQ column with 3 μm particle size, placed in an oven at 40°C and perfused with 82% mobile phase A (acetonitrile–H2O; 90:10, v/v) + 0.4% acetic acid and 18% mobile phase B (deionized H2O) + 0.2% formic acid at a flow rate of 340 μl/min in isocratic mode. The injected volume was 4 μl and the run lasted 4 min. The method was linear from 0.1 to 20 ng/ml and the lower limit of quantification was 0.1 ng/ml for all analytes. The method was applied to evaluate the plasma levels of catecholamines in plasma of patients with chronic kidney disease and allowed the detection for the first time of circulating levels of the novel catecholamines 6‐bromodopamine and 6‐cyanodopamine. [ABSTRACT FROM AUTHOR]