Colourimetric and AAS determination of cephalosporins using Reineck's salt

Abstract

Two simple, accurate, sensitive and selective procedures for the determination of eight cephalosporins are described. These procedures are based on the formation of ion-pair complexes between the drugs and ammonium reineckate, the formed precipitates are quantitatively determined either colourimetrically or by atomic absorption spectrometrically. The methods consist of reacting drugs with Reinecke's salt in an acidic medium at 25±2°. The first colourimetric procedure (procedure I) is based on dissolving the formed precipitate with acetone, the volume was completed quantitatively and the absorbance of the solution was measured at 525 nm against pure solvent blank. Also, the formed precipitates on the atomic absorption spectrometric procedure (procedure II) are quantitatively determined directly or indirectly through the chromium precipitate formed or the residual unreacted chromium in the filtrate at 358.6 nm. The optimum conditions for precipitation have been carefully studied. Beer's law is obeyed for the studied drugs in the range 5–35 μg ml⁻¹ with correlation coefficients ≮0.9989. Both procedures I and II hold well accuracy and precision when applied to the analysis of the cited cephalosporins in different dosage forms with good recovery percent ranged from 98.7±0.90 to 100.1±0.74 without interference from additives.

Introduction

Cephalosporins are penicillinase-resistant antibiotics with significant activity against Gram positive and Gram negative bacteria [1]. Cephalosporins were determined by titrimetric [2], [3], [4], [5], spectrophotometric [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], fluorimetric [17], [18], [19], [20], chromatographic [21], [22], [23], [24], [25], potentiometric [26] and polarographic [27], [28] methods.

Reineck's salt is ammonium tetrathiocyanotodiamminochromate (III) monohydrate in which it can be used for quantitative determination of many pharmaceutical compounds applying gravimetric [29], titrimetric [30] and spectrophotometric [31], [32], [33], [34], [35] procedures.

The purpose of the present work is to describe the development of the two simple and accurate spectrophotometric procedures, as well as a selective and sensitive atomic absorption spectrometric procedure, for the analysis of the titled antibiotic in the pure form as well as in pharmaceutical preparations.