Quantitative liquid chromatographic determination of intact cisplatin in blood with microwave-assisted post-column derivatization and UV detection

The anticancer agent cisplatin (cis-diamminedichloroplatinum(II), cis-[PtCl₂(NH₃)₂]) easily undergoes ligand-exchange reactions, resulting in mainly inactive Pt complexes. This paper presents a method for selective analysis of intact cisplatin in blood using LC and UV detection. Blood samples (hematocrit: 0.22-0.52) were spiked with cisplatin (final concentrations: 2.48 × 10⁻⁷ M-9.90 × 10⁻⁶ M) and subjected to centripetal ultrafiltration. The blood ultrafiltrate was separated (loop volume: 5 μl) with a porous graphitic carbon column and a mobile phase of HEPES-buffer (pH 9.3). Prior to UV detection (344 nm), the eluate was mixed with sodium N,N-diethyldithiocarbamate (DDTC) in a microwave field (115 °C) in order to improve the UV absorptivity. Cisplatin eluted as a Pt-DDTC complex after 11.8 min. The peak area was influenced primarily by the hematocrit, the DDTC concentration, and the temperature and residence time in the microwave cavity. The method was robust and sensitive provided preparing a fresh DDTC solution each day and, at the end of a day's run, destroying DDTC remaining in the system. It offers the main advantages of high selectivity, sensitivity, and robustness, minimal sample processing, and the possibility to use small sample volumes.