Quantitation of the antitumor agent N-(phosphonacetyl)-L-aspartic acid in human plasma and urine by gas chromatography-mass spectrometry-selected ion monitoring.

N-(Phosphonacetyl)-L-aspartic acid (PALA) is an antitumor agent which is currently under clinical study. A gas chromatography--mass spectrometry--selected ion monitoring assay procedure using [13C]PALA as the internal standard has been developed for the quantitation of PALA in biological samples. Standard curves which related ion intensity peak height ratios (m/e 220/221) to PALA concentrations in plasma and urine were described by a non-linear least square analysis with correlation coefficients of R2 greater than 0.