Analysis of Cisplatin and its Variants in Water
Data courtesy of Prof. Ryuji Kato, Ph D., Laboratory of Cardiovascular Pharmacotherapy and Toxicology, Osaka University of Pharmaceutical Sciences
COSMOSIL πNAP uses a naphthalene-based bonded phase, and exhibits different retention behavior from C18.
In this note, πNAP is used to analyze cisplatin (CDDP) and its mono-chloro, none-chloro (hydration complex), and OH-dimer forms in water.
Standard C18 columns have difficulty separating compounds of similar hydrophobicity. Perfomance may be improved by using Cholester, a column with improved molecular shape recognition.
Experiment Summary
Cisplatin (CDDP) in water converts to its mono-chloro, hydration complex, and OH-dimer forms, and it is thought that they exist in an equilibrium state (fig. 1). Each of these forms was separated and quantified.
![Cisplatin reactions in water](./img/cisplatin-reactions.png)
In water, CDDP loses Cl-, which is replaced with water. Depending on the pH, it may be replaced by a hydroxide ion. The mono-chloro form may lose another Cl-, and, in the same way, the water molecules (one or both) may be replaced with a hydroxide ion. These forms are in equilibrium.
Quantification of Cisplatin (CDDP) and its Mono-Chloro, None-Chloro, and OH-Dimer Forms
Comparing a C18 column, COSMOSIL Cholester, and πNAP under identical conditions
When measuring the OH-dimer nitrate form, the dissociated NO3- peak elutes before the OH-dimer peak. C18-MS-II could not separate the two peaks, and Cholester achieved partial separation, but could not separate to baseline. πNAP, however, was able to separate the compounds completely.
![C18 chromatogram](./img/cisplatin-app1.png)
Analysis Using COSMOSIL πNAP
Below is a typical chromatogram; the peak separation was excellent. The calibration curve for cisplatin (CDDP) was linear in the range of 0.01 to 4 mM, and the CV values for within-day and between-day variation were within 5%.
![πNAP chromatogram](./img/cisplatin-app2.png)
Observations
By using COSMOSIL πNAP, it is possible to separate and quantify cisplatin (CDDP) and its mono-chloro, none-chloro, and OH-dimer forms using HPLC.
References
Kato R. et al. A Novel Analytical Method of Cisplatin Using the HPLC with a Naphthylethyl Group Bonded with Silica Gel (πNAP) Column. Biol Pharm Bull. 40(3), 290-296(2017). DOI