High-performance liquid chromatographic procedures for the analysis of carboplatin in human plasma and urine

Specific, sensitive and reproducible high-performance liquid chromatographic procedures were developed for the quantitative analysis of carboplatin in human plasma and urine. Plasma and urine were ultrafiltered with an Amicon Centrifree micropartition system, and samples were injected onto a LiChrosorb diol column. The mobile phase was CH3CN/H2O (92:8, v/v) for plasma and CH3CN/0.015% H3PO4 (89:11, v/v) for urine. The effluents were monitored at 229 nm. Carboplatin eluted by 10 min. The detector response was linear from 0.5 (plasma) or 5 (urine) to 500 micrograms/ml. The lower limit of quantification was 1.0 micrograms/ml plasma and 5.0 micrograms/ml urine. Constituents in plasma and urine, and possible degradation products (cyclobutane mono- and dicarboxylic acids) did not interfere. Within-day precision was less than 4% for plasma and 9% and 4% for urine concentrations of 40 and 401 micrograms/ml, respectively. Within-day accuracy was 96% or greater for both matrices. Carboplatin was not bound to the Centrifree membrane and recovery was 94% for plasma and 96% for urine. The storage stability of carboplatin in water, plasma, plasma ultrafiltrate, and urine and the extent of binding to human plasma proteins were evaluated. The percentage of carboplatin reversibly bound to plasma proteins was minimal (less than or equal to 10%) over a range of 1-50 micrograms/ml. In human plasma at 37 degrees C the drug was stable for about 2 h, but then degraded with a half-life of 32 h. Carboplatin had limited stability in water, plasma, and urine stored at -25 degrees C. Biological samples, therefore, should be stored frozen and analyzed within a week of collection to obtain valid results.