Simple Sensitive Spectrophotometric Determination of Isoniazid and Ritodrine Hydrochloride

A novel coupling reagent was used for simple, rapid, and sensitive spectrophotometric determination of isoniazid (1NH) and ritodrine hydrochloride (RTH) in pure form or in pharmaceutical preparations of it. The method is based on the diazotization of 4,4-methylene-bis-m-nitroaniline followed by a coupling reaction with either INH or RTH in hydrochloric acid medium. The resulting colored products have absorption maxima at 495 and 473 nm, respectively. Beer's law is obeyed in the concentration ranges of 0.1–15 µg/mL and 0.1–17 µg/mL. The method is applied for the analysis of INH/RTH in pharmaceutical preparations and the results agree favorably with the official and reported data. Common excipients used as additives in pharmaceuticals do not interfere in the proposed method. The method offers the advantages of simplicity, rapidity, and sensitivity without the need of extraction or heating.