Determination of Digitoxin in Human Serum Using Stable Isotope Diluted Liquid Chromatography/Electrospray Ionization‐Tandem Mass Spectrometry

Abstract

Abstract A method for the determination of digitoxin in human serum using a liquid chromatography/electrospray ionization‐tandem mass spectrometry (LC/ESI‐MS/MS) technique is reported. Digitoxin and the internal standard, [21,21,22‐2H3]digitoxin, were extracted from 200 µL of human serum using a solid phase extraction cartridge and analyzed by LC/ESI‐MS/MS in the selected reaction monitoring mode. The intra‐ and inter‐assay reproducibility and accuracy were satisfactory within the quantification range of 5–100 ng/mL, which was sensitive enough to measure the digitoxin in real samples. The concentrations of digitoxin in serum samples obtained from digitalized patients (n=19) were in the range of 5.3–24.1 ng/mL, and these correlated well with those obtained by radioimmunoassay using a very specific antiserum.