doiSerbia

Acid-base equilibria of 2,4-diiodo-6-methylphenylcarbamoylmethyl iminodiacetic acid and its labeling with technetium-99m

Brborić Jasmina S. (Farmaceutski fakultet, Beograd)
Jovanović Mirjana S. (Institut za nuklearne nauke „Vinča', Laboratorija za radioizotope, Beograd)
Popović Gordana V. (Farmaceutski fakultet, Beograd)
Kapetanović Vera P. (Farmaceutski fakultet, Beograd)
Vladimirov Sote M. (Farmaceutski fakultet, Beograd)

The acid-base equilibria of a novel hepatobiliary imaging agent, 2,4-diiodo-6-methylphenylcarbamoylmethyl iminodiacetic acid (DIIODIDA) were studied. The potentiometrically determined acidity constants of the second carboxylic group, amino and amide groups were pK2 = 2.52 ± 0.02; pK3 = 5.86 ± 0.06 and pK4 = 10.9 ± 0.1. The determinations were performed at 25 ºC and an ionic strength of 0.1 mol/dm3 (NaCl). The acidity constants (pK1 = 1.3 ± 0.4) corresponding to the first carboxylic group was determined indirectly, on the basis of equilibrium constants obtained in a heterogeneous system, at 25 ºC and an ionic strength 1 mol/dm3 (HCl, NaCl). DIIODIDA was labeled with technetium-99m, and the influence of pH on the yield of labeling was investigated. It was found that labeling within the pH range from 5.5 to 6.5 provided a radiopharmaceutical of high radiochemical purity (>98 %).

Keywords: iminodiacetic acid analogues, acidity constants, hepatobiliary agent, technetium-99m