Three botanical reference materials prepared by the National Bureau of Standards have been studied by neutron activation analysis
to evaluate their suitability with respect to the determination of vanadium in biological samples. Various decomposition methods
were applied in connection with chemical or radiochemical separations, and results for vanadium were compared with those found
by purely instrumental neutron activation analysis. Significantly lower results indicate losses or incomplete dissolution,
which makes SRM 1575 Pine Needles and SRM 1573 Tomato Leaves less satisfactory than SRM 1570 Spinach. A reference value of
1.15 mg/kg of this material is recommended, based on results from 3 different methods. All three materials are preferable
to SRM 1571 Orchard Leaves, while Bowen's Kale remains the material of choice because of its lower concentration.