Development and Validation of an HPLC Method for Determination of Amifostine and/or Its Metabolite (WR-1065) In Human Plasma Using OPA Derivatization and UV Detection

A rapid, sensitive and reproducible HPLC method was developed and validated for the analysis of amifostine (AMF) and/or its metabolite, WR-1065 in human plasma. The method involves the alkylation of free sulfydryl group with iodoacetic acid followed by derivatization of the drug and its metabolite with o-phthaldialdehyde (OPA) and UVdetection at 340 nm. The derivatized AMF and WR-1065 were eluted in less than 11 min, and in the case of the metabolite with no interferences from the endogenous plasma peaks. Cystein was used as the internal standard. Analysis was carried out on a Eurosphere Performance (RP-18e, 100 × 4.6 mm) analytical column. The mobile phase was a mixture of methanol and phosphate buffer 0.03 M pH = 2.7 at a ratio of 40: 60v/v, respectively, with a flow rate of 1.5 mLmin-1. Limit of detection was 0.5 µgmL-1. The method involved a simple extraction procedure for AMF and/or its metabolite and analytical recovery was 90 ± 0.9%.The calibration curve was linear over the concentration range of 1-200 µgmL-1. The coefficients of variation for intra-day and inter-day assays were less than 10%.