The Color Reaction of Purine Bases by Ternary-complex Formation with Eosin and Silver(I)

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Abstract
A color reaction of purine bases utilizing a ternary-complex system among a purine base, a metal ion, and a xanthene dye was studied, and the fundamental conditions for the spectrophotometric determination of purine bases(as adenine) with eosin and silver(I) were established. The absorption maxima of the ternary-complexes lie at 550–560 nm against water. The optimum pH ranges for the color formation of the complexes are pH 4.8–5.4. Beer’s law is obeyed over the range of 1–10 μg/10 cm3 of adenine, and the apparent molar absorptivity is 1.1×105 dm3 mol−1cm−1 at 560 nm. In the determination of adenine, the coexistence of pyrimidine bases, such as uracil and cytosine, and nucleotides containing adenine, such as 5′-adenosine triphosphate(ATP) and β-nicotinamide–adenine dinucleotide(NAD), scarcely interfere.