Quantitative Analysis Using a Flatbed Scanner: Aspirin Quantification in Pharmaceutical Tablets

Here, students determine aspirin (acetylsalicylic acid) mass in pharmaceutical tablets using a colorimetric method. Aspirin, salicylate, and salicylic acid do not absorb visible light. Thus, in alkaline medium, acetylsalicylic acid was hydrolyzed to salicylate; then, it was reacted with an acidic Fe(III) solution, and a violet complex was formed. Quantitative analysis was carried out using absorbance measured at 535 nm (standard method) and digital images obtained with a flatbed scanner (proposed method). Results obtained with both methods were compared using an F-test and a t-test; both methods had shown equivalent accuracy and precision at the 95% confidence level. In addition, one-way ANOVA showed that aspirin masses found by five student groups using both methods are equivalent at the 95% confidence level. In the proposed method, samples were placed in a 96 microwell plate, and RGB values were extracted automatically from all wells in less than 5 min using ImageJ's plugin ReadPlate; data obtained were organized using a spreadsheet to determine aspirin mass in pharmaceutical tablets, recovery, and percent error. Our goal was to design a portable, cost-effective, and user-friendly platform and to develop an experimental methodology that can easily be applied to any research and education laboratory using just a flatbed scanner.