Colorimetric Determination of Free Salicylic Acid in Aspirin and Urine by Scanometry as a New, Reliable, Inexpensive and Simple Method

Abstract

A sensor array composed of individual cylindrical cavities in a sheet of Plexiglas®, which served as tiny reaction compartments, has been developed previously by Abbaspour, et al. [39–41] based on holes created in the matrix sheet by laser beam. The cells containing sample solutions were scanned with a usual flatbed scanner, and then the obtained color image of each cell was analyzed with software written in Visual Basic (VB 6) media in red, green and blue (RGB) values. In this work, this simple, fast and inexpensive method has been used for determining free salicylic acid in aspirin tablets and urine in ferric nitrate solution. The results showed that Fe(III) forms a colored 1 : 1 complex with salicylic acid and the system response is linear in a concentration range of 2 – 280 μg/L of salicylic acid with a detection limit of 0.84 μg/L for pH in the range of 2.2 – 2.4. The scanner was used instead of a spectrophotometer and a series of interferences was examined.