Synthesis of the isotope‐labeled derivatization reagent for carboxylic acids, 7‐( N , N ‐dimethylaminosulfonyl)‐4‐(aminoethyl)piperazino‐2,1,3‐benzoxadiazole (d 6 ) [DBD‐PZ‐NH 2 (D)], and its application to the quantification and the determination of relative amount of fatty acids in rat plasma samples by high‐performance liquid chromatography/mass spectrometry

The isotope‐labeled benzofurazan derivatization reagent for carboxylic acids, 7‐( N , N ‐dimethylaminosulfonyl)‐4‐(aminoethyl)piperazino‐2,1,3‐benzoxadiazole (d 6 ) [DBD‐PZ‐NH 2 (D)] was synthesized. DBD‐PZ‐NH 2 (D) was used for the accurate quantification of fatty acids by liquid chromatography/mass spectrometry (LC/MS). The standard fatty acids were derivatized with DBD‐PZ‐NH 2 (D) to the stable isotope‐labeled compounds for the fatty acids derivatives of DBD‐PZ‐NH 2 and used for the internal standards. The obtained calibration curves for fatty acids were linear over the range 0.1–200 µ M ( r 2 > 0.999). Fatty acids in plasma samples were determined after derivatization with DBD‐PZ‐NH 2 and analyzed by LC/MS using standard fatty acid DBD‐PZ‐NH 2 (D) derivatives as internal standards. Furthermore, the relative amounts of fatty acids in two plasma samples were determined after derivatization with DBD‐PZ‐NH 2 and DBD‐PZ‐NH 2 (D). The isotope‐labeled derivatization reagent was useful for accurate quantification and the determination of relative amounts of the metabolites in biological samples having the target functional group. Copyright © 2005 John Wiley & Sons, Ltd.