Absorptiometric Determination of Acetylsalicylic Acid in Aqueous Ethanolic Solution

Abstract

Acetylsalicylic acid (ASA) was found to be quite soluble and quite stable in a 50/50% volume/volume water–ethanol solution. In this solution, a well-defined spectrum with a maximum absorbance, λ_max, of 276 nm of ASA was observed, and a molar absorptivity, ε, of 1.1 × 10³ M-cm was determined. These characteristic physical properties were used to determine ASA concentration in different brands of aspirin. The λ_max and the ε of salicylic acid were also determined. The characteristic values determined were 300 nm and 3.83 × 10³ M-cm, respectively. In this solution and using the method developed here, the concentrations of salicylic acid and ASA in a given aspirin formulation can be determined simultaneously.

Keywords:

• Absorbance
• acetylsalicylic acid
• aspirin
• molar absorptiometry
• salicylic acid
• UV-vis
• wavelength

The author is grateful to the EARDA/NIH (Extramural Associates Research Development Award/National Institute for Health) of Morgan State University for support of this work.