Keywords : histidine

Spectrophotometric Determination of Paracetamol Using Diazotization Coupling Reaction

Enas S. Thanoon

Rafidain Journal of Science, 2019, Volume 28, Issue 2, Pages 76-83
DOI: 10.33899/rjs.2019.159979

An accurate, simple, and sensitive indirect spectrophotometric method which proposed and developed for the determination of paracetamol in different pharmaceutical preparations. The proposed method was based on acid hydrolysis of PAR to produced p-aminophenol (PAP), PAP was diazotization with nitrite ion to form the corresponding diazonium salt, followed by coupling with histidine reagent in alkaline medium to produced azo dye that showed maximum absorbance at 430 nm. Beer's law was obeyed in the concentration rage of 10-500 µg/20 ml (i.e. 0.5-25 ppm). The molar absorpitivity and Sandell's sensitivity of the dye were. 1.118×104 0.0135 µ respectively. The method successfully has been applied for the determination of PAR in pure form,and its pharmaceutical preparations (tablets, syrup and injection).


Spectrophotometric Determination of Mesalazine

Safaa A. Al-Zakaria

Rafidain Journal of Science, 2019, Volume 28, Issue 2, Pages 127-134
DOI: 10.33899/rjs.2019.159982

Mesalazine (MESA) is determined by a simple and rapid visible spectrophotometric method. This method is depend on oxidative coupling reaction of mesalazine with histidine (HIS) in alkaline media using N-bromosuccinimide (NBS) as oxidizing agent to form a water soluble and stable product, that it has a maximum absorption at 459 nm. Beer's law is followed in a concentration range of 50 to 750 μg /20ml (2.5-37.5 μg /ml) with a molar absorptivity of 3.3682×103 l.mol-1. cm-1. The recommended method has been successfully applied to the assay of MESA in pharmaceutical preparations.