Development of HPLC conditions for valid determination of hydrolysis products of cisplatin

In water, the antineoplastic drug cisplatin, cis-[PtCl2(NH3)(2)] (1) hydrol yses slowly to the aqua complexes cis-[Pt(NH3)(2)Cl(H2O)](+) (2) and, to a small extent, cis-[Pt(NH3)(2)(H2O)(2)](2+) (3), which are thought to play a n important role in the metabolism of cisplatin. HPLC is a useful technique for monitoring 2 and 3, but only if the components of the mobile phase use d in the reverse phase HPLC technique are unreactive toward these aqua comp lexes under the conditions of the experiment. N-15 Nuclear magnetic resonan ce (NMR) with samples highly enriched (>98%) in N-15 has been used to check the reactivity of 2 and 3 toward substances commonly used as components of the mobile phase. The results reported herein indicate that acetonitrile, often used as an organic modifier, reacts readily with 2 and 3. Methanol, a lso commonly employed, is much less reactive. Carboxylic acids RCO2H (R = C H3, H, CF3), which are frequently used to adjust pH of the mobile phase, al so react readily with 2 and 3. Trifluoromethanesulfonic acid ("triflic acid "), CF3SO3H, is unreactive. Neither hexanesulfonic acid nor sodium dodecyl sulfate (SDS), used as "ion-pairing agents", reacts significantly with 2 or 3 under the experimental conditions, but SDS gives better peak separation. Commercial SDS must, however, be purified from chloride contamination. Fro m our studies, optimal conditions for HPLC separation of 1, 2, and 3, with a Gls stationary phase at 37 degrees C, require an aqueous mobile phase wit h 3% v/v methanol, 0.05 mM SDS, and pH 2.5 (adjusted with triflic acid). Th is technique was then used to measure revels of 1, 2, and 3 in ultrafiltere d serum after incubation for Various times with cisplatin at 37 degrees C.