Graphene oxide-based solid phase extraction of vitamin B<sub>12</sub> from pharmaceutical formulations and its determination by X-ray fluorescence.Published in:XRS: X-ray Spectrometry, 2015, v. 44, n. 1, p. 16, doi. 10.1002/xrs.2572By:Moradi, Morteza;Zenouzi, Soraya;Ahmadi, Kamran;Aghakhani, AliPublication type:Article