Simultaneous analysis of angiotensin peptides by LC–MS.pdf

ANALYTICAL BIOCHEMISTRY Analytical Biochemistry 369 (2007) 27–33 /locate/yabio Simultaneous analysis of angiotensin peptides by LC–MS and LC–MS/MS: Metabolism by bovine adrenal endothelial cells Lijie Cui, Kasem Nithipatikom, William B. Campbell * Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226, USA Received 14 February 2007 Available online 5 July 2007 Abstract Liquid chromatography–electrospray ionization–mass spectrometry (LC–ESI–MS) and liquid chromatography–tandem mass spec- trometry (LC–MS/MS) methods were developed to simultaneously determine the concentrations of angiotensin (Ang) II, Ang 1-7, Ang III, and Ang IV in biological samples. The samples were extracted with C18 solid-phase extraction cartridges and separated by a reverse-phase C18 column using acetonitrile in water with 0.1% formic acid as a mobile phase. Ang peptides were ionized by electro- spray and detected by triple quadrupole MS in the positive ion mode. (M + 3H)3+ and (M + 2H)2+ ions were chosen as the detected ions in the single ion recording (SIR) mode for LC–MS. The limits of detection (signal/noise [S/N] = 3) using SIR are 1 pg for Ang IV and 5 pg for Ang 1-7, Ang III, and Ang II. Multiple reaction monitoring (MRM) mode was used for LC–MS/MS. The limits of detection (S/N = 3) using M