Potentiometric Determination of Lobenzarit in Bulk Drugs

Abstract

A new and easy potentiometric technique for the quantitative analysis of disodium lobenzarit (1). a recognized antirheumatic agent in bulk drug, is reported. A standardized solution (0.1 M) of hydrochloric acid (HCl) was used as titrating agent and a mixture of water and 1,4-dioxane (1:3) was used as solvent. The linear range was established between 40 and 120 mg (r=0.999). The technique was sensitive (0.059 mL of HCl per mg of I, which agrees with theoretical calculation), precise (repeatability, CV = 0.3% and reproducibility, CV = 0.61 and 0.71%) and accurate (100% of analyte was recovered). The technique was used for the determination of I in the presence of up to 2% of related compounds from the synthesis (sodium 2,4 – dichlorbenzoate (II) and antranilate (III)), but it was not able to detemine I in the presence of degraded compounds. Nevertheless, this technique could be used for the determination of purity, if the absence of these compounds is demonstrated. For this purpose, an alternative high performance thin layer chromatographic technique is also proposed.

Key Words:

• lobenzarit
• 4-chloro-2,2′-iminodibenzoic acid
• potentiometry
• reference standard
• validation
• chemical quantitative analysis.