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

• Main Authors: S. VLADIMIROV, V. KAPETANOVIC, G. POPOVIC, M. S. JOVANOVIC, J. S. BRBORIC
• Format: Article
• Language: English
• Published: Serbian Chemical Society 2006-01-01
• Series: Journal of the Serbian Chemical Society
• Subjects: iminodiacetic acid analogues; acidity constants; hepatobiliary agent; technetium-99m
• Online Access: http://www.shd.org.yu/HtDocs/SHD/Vol71/No1/JSCS_V71_No1-06.pdf

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 %).