A novel and secure indirect spectrophotometric technique for estimation of naproxen as a coupled compound with paracetamol as a unharmed diazotized reagent than organic reagents. Naproxen was first converted into an active form to act as coupling agent by reflux with hydrobromic acid (HBr) and acetic acid (CH3COOH) to yield the Hydroxy Form of Naproxen (HFN).
The diazotized complex absorb light in wavelength 500 nm. Beer's law linearity is 10 to 200 µg/20ml, (i.e. 0.5-10.0 ppm), the molar absorptivity (ɛ) is 2.14x104 l/mol.cm, Sandell's sensitivity index (SSI) is 0.0094 µg/cm which indicate a high sensitivity, RSD more than ±0.36 % indicate good precision and higher accuracy (relative error more than 0.82 %), and LOD = 0.024 µg/ml and LOQ = 0.079 µg/ml. The technique has been used effectively for estimation of naproxen in tablets.