Direct Analysis of Platinum in Plasma and Urine by Electrothermal Atomic Absorption Spectrophotometry*f

An im proved technique is described for analysis of platinum (Pt) con centrations in plasma and urine by electrotherm al atomic absorption spec trophotom etry (EAAS). The m ethod is intended for use in therapeutic m onitoring of cancer patients treated with platinum-containing antitum or drugs. Samples (0.1 ml) of plasma, urine, or Pt standards are diluted to two ml with a matrix solution that contains diammonium edetate, ammon ium dihydrogen phosphate, ammonium hydroxide, and octoxynol d e te r gent. Concentrations of P t in the diluted samples are determ ined directly by EAAS analysis with Zeeman background correction. Standard additions are unnecessary; Pt concentrations are read from a calibration chart of peak heights, which is linear up to 1.6 mg per liter. The detection limit is 0.02 mg of P t p e r liter. Day-to-day precision (coefficient of variation, based on 21 consecutive runs) ranges from 4.2 to 11.7 percent, depending upon the P t concentration in the plasma and urine specimens. Recovery of Pt added to plasma and urine specimens averages 103 ± 8 and 99 ± 6 percent, respectively. Concentrations of Pt are stable in plasma and urine specimens stored at 4°C or — 20°C for four weeks. Analyses of P t concen trations in serial plasma and urine specimens from cancer patients receiv ing cisplatin chem otherapy dem onstrate the clinical utility of the tech nique