Direct analysis of platinum in plasma and urine by electrothermal atomic absorption spectrophotometry

An improved technique is described for analysis of platinum (Pt) concentrations in plasma and urine by electrothermal atomic absorption spectrophotometry (EAAS). The method is intended for use in therapeutic monitoring of cancer patients treated with platinum-containing antitumor drugs. Samples (0.1 ml) of plasma, urine, or Pt standards are diluted to two ml with a matrix solution that contains diammonium edetate, ammonium dihydrogen phosphate, ammonium hydroxide, and octoxynol detergent. Concentrations of Pt in the diluted samples are determined 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 Pt per liter. Day-to-day precision (coefficient of variation, based on 21 consecutive runs) ranges from 4.2 to 11.7 percent, depending upon the Pt 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 degrees C or -20 degrees C for four weeks. Analyses of Pt concentrations in serial plasma and urine specimens from cancer patients receiving cisplatin chemotherapy demonstrate the clinical utility of the technique.