Performance characteristics of an LC-MS/MS method for the determination of plasma metanephrines.

BACKGROUND: Catecholamines and their metabolites, metanephrines, are produced excessively in pheochromocytoma tumors of the chromaffin cells. Increased concentrations of these compounds produce symptoms and allow for clinical evaluation of disease. Historically, screening for such tumors by determination of catecholamines and metabolites in urine yielded false negative results in individuals with a genetic predisposition for the disease and those with paroxysmal hypertension. Analysis of metanephrines in plasma, however, is of decisive diagnostic importance. This test exhibits high sensitivity and specificity for the analytes produced by tumors. METHODS: Plasma proteins are removed by solid phase extraction. Chromatographic isolation of the analytes and stable isotope internal standards is achieved by elution on a HILIC column connected to a UPLC MS/MS system. Metanephrines are measured using multiple reaction monitoring with an electrospray source operating in positive ion mode. RESULTS: The method was validated for linearity, limit of quantification, accuracy, and precision. The method was accurate and correlated well to a comparison HPLC method. Potential interferences were evaluated. CONCLUSIONS: Results from this LC-MS/MS assay enable clinical diagnosis of pheochromocytoma and aid in monitoring treatment outcomes.

Mass spectrometric study of dirhenium biscarboxylate:purine dinucleotide complexes.

Dirhenium adducts of purine dinucleotides were identified by mass spectrometry. In consecutive studies, Re(2)(O(2)C(2)H(3))(2)Cl(4) . 2H(2)O was reacted with 2'-deoxyguanylyl(3'-->5')-2'-deoxyguanosine (dGpG) and 2'-deoxyadenylyl(3'-->5')-2'-deoxyguanosine (dApG) in H(2)O or D(2)O. These reactions were monitored to identify novel dinuclear rhenium:dinucleotide complexes as confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), electrospray ionization mass spectrometry (ESI-MS) and collision-induced dissociation tandem mass spectrometry (CID MS/MS) experiments. However, the most abundant adducts detected by ES-MS were dirhenium:nucleotide species. Of these, guanine-containing ions were observed with highest ion counts suggesting a preference for guanine coordination. Dimetal adducts showed coordination of the purine bases and common metalated fragments were observed for both dGpG and dApG reactions.