Determination of ruthenium on DNA by XRF.

An X-ray fluorescence (XRF) technique is used to quantitate the binding of [H2O(NH3)5Ru(II)](2+) to DNA. This method is shown to be more sensitive, precise, and convenient than conventional optical absorption (OA) spectroscopy, differential pulse voltammetry (DPV), or atomic absorption (AA) techniques. X-ray fluorescence is insensitive to the oxidation state or coordination environment of Ru and so can be used to determine total Ru. The minimum detectable amount of Ru is 10 ng in 1 h of counting time, using a 100-mCi(125)I source. The specific advantages of the XRF method over the conventional methods are outlined.