Fluorimetric determination of magnesium by ternary complex formation with pyridoxal nicotinylhydrazone and amines

The synthesis, characteristics and analytical applications of pyridoxal nicotinylhydrazone are described. This compound reacts with magnesium(II) in the presence of ammonia, ethylenediamine or pyridine, to produce a 1:1:1 Mg(II)—pyridoxal nicotinylhydrazone—amine fluorescent complex (λ_ex 395 nm, λ_em 480 nm). A fluorimetric method is proposed for the determination of magnesium(II) (20–100 ng ml^-1 in the solution measured); isobutanol is used to extract the complex, reducing the number of interferences.