Simultaneous determination of Pt and I by ICP-MS for studies of the mechanism of reaction of diiodoplatinum anticancer complexes

The determination of Pt by ICP-MS in environmental and biological samples i s well documented and generally performed after dissolution in dilute HNO3. On the other hand, I is poorly ionised in the plasma and, at low pH? memor y effects and instability arise from the formation of potentially volatile species, such as I-2 and HI, depending on the oxidation state of I. In orde r to investigate the role of iodo ligands in the design of Pt anticancer co mplexes, we have optimised conditions for the simultaneous determination of Pt and I. Standards and samples were diluted in 10 mM KOH and improved ion extraction into the quadrupole was achieved by means of an additional pump (S-Option(TM)), leading to about a 2-fold increased sensitivity. The limit s of detection in water were 10 and 0.6 ng l(-1) for I and PI, respectively , but. increased to 23 ng l(-1) for I and 2.2 ng l(-1) for Pt in KOH (10 mM ). The analysis of certified reference materials yielded the following resu lts: 0.84 +/- 0.05 mu g g(-1) I (certified value: 0.81 +/- 0.05 mu g g(-1)) in BCR CRM 063R 'Skimmed Milk Powder', and 0.121 +/- 0.006 mu g ml(-1) Pt (indicative value: 0.12 mu g ml(-1)) in NIST SRM 2670 'Toxic Metals in Urin e'. Pt:I ratios ranging from 0.240 to 1.035 were measured with an accuracy of 101.3 +/- 2.4%. The determination of the Pt:I ratio in the low M-r fract ion of reaction mixtures of diiodo Pt complexes and human albumin provided evidence for the release of iodide and for different kinetics for the react ions of diiodo Pt(rv) and Pt(rr) complexes.