| Abstract: | Abstract A quantitative method was developed for the assay of the bicarbonate content in a number of potassium-replacement effervescent tablets with citric acid. The method involved treatment of an aliquot of the crushed tablet with water, then with 0.5 N sulfuric acid, followed by quantitative absorption of the liberated carbon dioxide into 0.2 N sodium hydroxide in a closed system with a calcium chloride-protected vent. The sodium carbonate-sodium hydroxide solution was subjected to a two-step titration with standard acid using phenolphthalein and bromophenol blue indicators for the first and second step, respectively. Overall percent recovery (± SD) of potassium bicarbonate from simulated tablets were: 99.6 ± 0.9% (n = 4); in presence of potassium citrate, 100.0 ± 1.3% (n = 4); and in presence of potassium chloride and L-lysine hydrochloride, 101.5 ± 1.9% (n = 3). Application of the method to commercial products near the expiration date showed potassium bicarbonate contents of 80–90% of label claim. The method may be applied to the assay of any bicarbonate salt in other effervescent formulations. |
