Practical: Assay of an Aspirin tablet by UV spectrophotometer
1. Abstract
The purpose of the experiment is to analyze a commercially available aspirin tablet in order to ascertain its acetylsalicylic acid content. UV spectroscopy is a very useful method for quantitative analysis of drug substance. A standard calibration curve is used to determine the amount of aspirin in a commercial tablet. In 325 mg commercial tablet was estimated to have 292.5 mg which is equivalent to 270 mg for 300 mg. The % error in the analysis was determined to be 10%.
2. Introduction:
The purpose of the experiment is to analyze a commercially available aspirin tablet in order to ascertain its acetylsalicylic acid content.1 Aspirin is a non-steroidal anti-inflammatory drug (NSAIDs) which is used as a painkiller and originally discovered from salicylic acid known to have irritant to GIT and several undesirable side effects. It is a COX inhibitor, and the side effect is also attributed due to non-selectivity between COX-1 and COX-2 inhibition. Aspirin is chemically called by the name of acetylsalicylic acid. It is an ester of salicylic acid, which is prepared by the reaction of salicylic acid with acetic anhydride.2

In principle, UV spectroscopy depends on absorption of UV-Vis radiation which is directly proportional to concentration (Beer’s Lambert’ Law).

A = abc

Where A = absorbance
a = molar absorptivity
b = path length
c =concentration
An aqueous sodium hydroxide solution of aspirin was prepared which converted it to salicylate ion. Ferric chloride (FeCl3) solution was used to form the color complex with salicylate ion, and its intensity is directly proportional to the concentration of salicylic acid or aspirin. A standard calibration curve was prepared by serial dilution which can be used to find out the amount of aspirin in a tablet.

V. Questions 1. It is often safe to assume that the FID signal is...