Spectrophotometric Determination of Co(II) in Vitamin B12 Using 2-(biphenyl-4-Yl)-3-(2-(2,4-Dinitrophenyl) hydrazono)methyl) Imidazo [1,2-a]pyridine As Ligand by Flow Injection–Merging Zone Analysis. ANJS 2020, 23 (3), 24-38.