Determination of Organic Compounds by Atomic Absorption Spectrophotometry (AAS) with Special Reference to Compounds Encountered in Environmental Problems

Abstract

A comprehensive review of the indirect methods for the determination of organic compounds by atomic absorption spectroscopy is given. The various techniques used are summarised, two examples chosen and discussed in detail in order to demonstrate the feasibility of the method. Saccharin, an important artificial sweetener, and common food additive, may be determined by atomic absorption spectroscopy via complexation as its tris-(1,10-phenanthroline)iron(II) cation. The other subject chosen for study was the possible determination of certain N-nitrosamines. These are carcinogenic substances formed by the interaction of organic secondary amines with nitrite salts. In the present work, the spectrophotometric determination of saccharin by selective solvent extraction from aqueous solutions containing an excess of tris-(1,10-phenanthroline)-iron(II) cation into nitrobenzene as an ion-association system, has been thoroughly investigated in order to determine the optimum conditions. This method has been adapted to give an atomic absorption spectroscopy finish using both flame and flameless techniques, in which both the organic and aqueous phases have been analysed. Furthermore, a new simple, rapid and accurate spectrophotometric procedure for the determination of saccharin has been devised utilising the fact that "ferroin" is strongly adsorbed on silica gel. The procedure is based on the quantitative formation of the ion-association complex (Fe phen3)2+, (saccharin)2, when an acetone (70%) or methanolic (86%) or ethanolic (60%) solutions of saccharin is shaken with ferroin-impregnated silica gel matrix. Desorption of the ion-association complex is then carried out and the absorbance is measured at 510nm. A further development of the adsorption method is described in which the desorbed complex is analysed by atomic absorption spectroscopy instead of a spectrophotometric procedure. A brief review of the spectrophotometric methods available for the determination of N-nitrosamines is given. Attempts to determine N-nitrosamines by atomic absorption spectroscopy via formation of some of their metal complexes is also reported.