Specific determination of intact cisplatin and monohydrated cisplatin in human plasma and culture medium ultrafiltrates using HPLC on-line with inductively coupled plasma mass spectrometry

We have developed a specific assay for cisplatin in human plasma ultrafiltrate (PUF) and cell culture medium ultrafiltrate (MUF) using HPLC on-line with inductively coupled plasma mass spectrometry (ICP-MS). Separation of cisplatin (6 min) and monohydrated cisplatin (12 min) was achieved using a muBondapak C(18) column (Waters) and a mobile phase (0.075 mM sodium dodecyl sulfate and 3% methanol, adjusted to pH 2.5 with triflic acid) pumped at a flow rate of 0.5 mL/min. The analytes were detected with little background interference by ICP-MS monitoring of platinum masses (m/z 194/195). Calibration curves were linear over three orders of magnitude (0.05-8 microM) and the limit of quantitation was 0.1 microM. Intra- and inter-assay accuracy (range 91.6-113%) and precision (range 1.00-12.3%) were acceptable for PUF and MUF. The method was applied to determining cisplatin during ex vivo incubation of the drug in whole human blood at 37 degrees C. In conclusion, a specific, sensitive and reliable HPLC-ICP-MS assay has been established for determining intact cisplatin in PUF and MUF.