Traceability in analytical chemistry: the link-up of a transfer solution to a reference solution by Instrumental Neutron Activation Analysis

The possibility of using Instrumental Neutron Activation Analysis to link-up a transfer elemental solution to a reference elemental solution was investigated. The measurement procedure was developed to reach the target 0.1% relative expanded uncertainty required for the determination of the ratio between the mass fractions of two elemental solutions. The use of a monitor element added to the elemental solution was essential to make the result independent on several experimental parameters, including the non-uniformity of the neutron flux at the irradiation positions. The proposed measurement procedure was tested in a neutron activation experiment using two Mo solutions with the same 1 mg g-1 mass fraction. Although the target uncertainty was not reached, the resulting ratio 0.9991(41) was in agreement with the expected unit value. According to the uncertainty budget, the 0.1% target seems to be achievable by adjusting the position of the samples during the g-counting.