Quantification and excretion kinetics of a magnetic resonance imaging contrast agent by capillary electrophoresis-mass spectrometry

A novel method for the analysis of Gadolinium‐based contrast agents in complex clinical matrices is presented. Three commonly applied ionic contrast agents for magnetic resonance imaging were separated by CE and detected by ESI‐MS. Blank urine samples were spiked with Dotarem® (Gd‐DOTA, Gadolinium‐1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid), Magnevist® (Gd‐DTPA, Gadolinium‐diethylenetriaminepentaacetic acid) and Multihance® (Gd‐BOPTA, Gadolinium‐benzyloxymethyl‐diethylenetriaminepentaacetic acid) to determine the recovery rates. The figures of merit were determined with LODs as low as 2.0×10−7 mol/L for Gd‐DOTA, 5.0×10−7 mol/L for Gd‐DTPA and 1.0×10−6 mol/L for Gd‐BOPTA. The respective LOQs were 6.6×10−7 mol/L for Gd‐DOTA, 1.5×10−6 mol/L for Gd‐DTPA and 3.3×10−6 mol/L for Gd‐BOPTA. The linear working range comprised two orders of magnitude starting at the LOQ, with regression coefficients of R≥0.999 for all investigated analytes. Using this CE‐MS method, Gd‐DOTA was quantified in seven urine samples obtained at different times after delivery from a volunteer magnetic resonance imaging patient who was treated with Dotarem®. Additionally, total Gd concentrations were determined by means of ICP‐optical emission spectroscopy to validate the CE‐MS data. To compensate for dietary dilution effects of the urine samples, creatinine was determined by HPLC with UV/Vis absorption detection. Gd‐DOTA concentrations were normalized to urinary creatinine, illustrating the fast excretion kinetics of Gd‐DOTA.