1990 Volume 39 Issue 1 Pages 37-41
Optimal conditions of separation for isoniazid and acylisoniazid derivatives (acetylisoniazid, propionylisoniazid, isobutyrylisoniazid, butyrylisoniazid, benzoylisoniazid) were determined in reversed-phase ion-pair LC. Sodium dodecanesulfonate was the best ion-pair reagent among alkylsulfonates. When the carbon number of alkylsulfonate was below 4, the elution order was isoniazid, acetylisoniazid and propionylisoniazid. When the carbon number of alkylsulfonate was 5, the elution order of isoniazid and acetylisoniazid was changed. Further when its number was 8, the elution order of isoniazid and propionylisoniazid was reversed. The acyl group of acylisoniazid also affected their retention. The conditions of HPLC were as follows : Column, Inertsil ODS-2 (5 μm, 150×4.6 mm i.d.); eluent, 24% aqueous acetonitrile solution containing 2.0 mM sodium dodecanesulfonate (pH 3); flow rate, 1.0 ml/min; column temperature, ambient. Retention time was 6.30 min for isoniazid, 3.69 min for acetylisoniazid, 4.49 min for propionylisoniazid, 6.06 min for isobutyrylisoniazid, 6.25 min for butyrylisoniazid and 12.58 min for benzoylisoniazid. The capacity ratios (log k') of isoniazid and acylisoniazid derivatives and the partition coefficients measured in 1-octanol/water (log P') were in good linear relation with those calculated by Rekker's hydrophobic fragmental constants (log P). Coefficient of correlation for firstorder regression lines of log P-log P', log k'-log P and log k'-log P' plots were 0.984, 0.997 and 0.996 (n=6), respectively. This calculation method could generally be used to find an appropriate internal standard compound for reversed-phase LC.
