Evaluation of Effective Parameters in Mass Bias for Increase of Accuracy in Isotopic Analysis of Uranium by ICP-TOF-MS

The accuracy of isotopic compositions measurement is affected by all the ICP-MS instruments because of the phenomenon known as mass bias, where it is defined as difference between the measured and true values in an isotopic analysis. This research has introduced mass bias and also evaluated the effective parameters including concentration of uranium, electrical field behind the second or skimmer cone, detector voltage, plasma power and nebulizer flow. The least mass bias with a relative error -0.3% for the isotopic analysis of uranium results in aqueous media without interference of the matrix with 1.2% RSD of 0.3 mg/L concentration, while the voltages of ion lens 1 and 2 in the ICP-TOF-MS were -700V and -550V, respectively. The instrument was set in the plasma power of 1000 watts, nebulizer flow of 0.78 ml/min, and the detector voltage of -2450V.