Spectrophotometric determination of 4-aminoantipyrine in aqueous solution by coupling with diazotised 4-nitroaniline

Abstract

A simple, rapid and sensitive spectrophotometric method for the determination of trace amounts of 4-aminoantipyrine in aqueous solution is described. The method is based on a coupling reaction between 4-aminoantipyrine and diazotised 4-nitroaniline to form an intense yellow, water-soluble dye that is stable and has a maximum absorption at 380 nm. A graph of absorbance versus concentration shows that Beer's law is obeyed over the concentration range 25–750 µg of 4-aminoantipyrine in a final volume of 25 ml (i.e., 1–30 p.p.m.) with a molar absorptivity of 1.3 × 10⁴ l mol^–1 cm^–1, a Sandell sensitivity of 156.4 × 10^–4µg cm^–2, a relative error of –0.8 to +1.5% and a relative standard deviation of 0.3–2.0% depending on the concentration. The optimum conditions for full colour development and the interference of foreign organic compounds have been investigated. The proposed method does not require either temperature control or a solvent extraction step.