Application of ternary complexes in pharmaceutical analysis

Summary The formation of a ternary complex of iron(III) with isoniazid-2-hydroxybenzaldehyde hydrazone(INSH) in a cetyltrimethylammonium bromide(CTAB) micellar medium, leads to a simple, sensitive and accurate spectrophotometric microdetermination of the iron(III), either in pure aqueous solutions or, particularly, in various anti-anaemic formulations. The apparent molar absorptivity of this complex and Sandell's sensitivity at 386 nm were 2.08×10⁴ lmol^–1 cm^–1 and 2.68 ngcm^–2, respectively. The calibration graph which was traced according to the regression line equation, A=3.70×10^–1 C+1.09×10^–3 (r=1.0000; n=28), was rectilinear for 100 ppb to 3.0 ppm of iron(III). The accuracy and the precision of the method could be considered as very satisfactory, since the mean CV% was 0.202 in the range 0.5–3.0 g of iron(III) per ml. The results obtained for iron(III) by the new method and by the o-phenanthroline method, were compared statistically by means of the Student t-test and the variance ratio F-test; no significant difference was found.Parts I and II see 6] and 7]