Losses of Cr content in plant samples using digestion procedures with acids

In the WEPAL IPE 2009.2 proficiency test, Jozˇef Stefan Institute (JSI) participated by measuring Cr by k0-INAA; it was the only laboratory providing data by an instrumental technique. The JSI Cr result was about 38% higher than the assigned value in plant sample 124 (Lucerne/Medicago sativum). The same sample was again studied in 2012. This time, more labs, including JSI, used instrumental techniques and the average Cr result was higher and consistent with the 2009 and 2012 JSI results. From the results obtained in the present study, involving four INAA labs, it is confirmed that Cr losses in this sample occurred during the chemical digestion required by the techniques applied by other laboratories, illustrating the inherent advantage of nuclear techniques to be almost matrix independent and independent of the chemical state of the element under study.