QUANTITATIVE BIOANALYSIS USING MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY

The application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for quantitative analysis was investigated with the use of internal standards. Three peptides/proteins in the mass range 1000-12000 were tested and the effect of various internal standards was evaluated. Horse cytochrome c was used as an internal standard for bovine cytochrome c, melittin for renin and an undecapeptide B analogue was employed as an internal standard for the decapeptide A. A linear response was found between the measured peak height ratio and the applied amount of analyte when an appropriate internal standard was used. The quantitative abilities of MALDI-MS were finally applied to the determination of the drug amperozide in plasma. The biological samples were prepared for analysis using liquid-liquid extraction prior to MALDI-MS. A linear calibration graph was obtained using the C-13(4) stable isotopically labelled amperozide as an internal standard.