Analytical Sciences

Ethyl Chloroformate as a Derivatizing Reagent for the Gas Chromatographic Determination of Isoniazid and Hydrazine in Pharmaceutical Preparations

Mohammad Yar KHUHAWAR and Liaquat Ali ZARDARI

Dr. M. A. Kazi Institute of Chemistry, University of Sindh Jamshoro, Pakistan

Ethyl chloroformate was examined as a precolumn derivatizing reagent for the gas chromatographic (GC) determination of isoniazid (INH) and hydrazine (HZ). Phenylhydrazine (PHZ) was used as an internal standard. GC separation was carried out on an HP-5 column (30 m × 0.32 mm i.d.) with flame ionization detection. The elution was carried out at an initial column temperature of 150°C for 1 min at a heating rate of 10°C/min up to 250°C, nitrogen flow rate of 4 ml/min and a split ratio of 10:1, v/v. The linear calibration ranges for INH and HZ were observed between 3.5 - 37.5 and 3.5 - 35 µg/ml with corresponding detection limits of 0.18 and 0.17 ng reaching the detector. The method was subsequently applied to the determination of INH and HZ in pharmaceutical preparations, achieving a relative standard deviation (RSD) of 3.8 - 5.8%. The recovery percentage of INH from isoniazid syrup was 98% with an RSD of 5.2%.

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