Light-absorption ratio variation approach to sensitive and selective determination of iron with trimethoxyphenylflurone, cetylpyridinium, and thioglycollic acid

The complexation between trimethoxyphenylflurone (TMPF) and Fe is highly sensitive at pH 11.80 in the presences of cetylpyridinium chloride (CPC) and thioglycolic acid (TGA), where TGA reduced TMPF into a reduced ligand (RTMPF) and Fe(III) into Fe(II). The complexations of RTMPF with CPC and Fe have been characterized by the break point approach and the spectral correction technique. The binuclear complex, Fe-2(RTMPF)(10)(CPC)(20) was formed via coordination bond and ion-pair attraction. The Fe-TMPF-CPC complexation is selective in the presence of ethylenediamine tetraacetic acid (EDTA) and AI(III) so it was applied to the spectrophotometric determination of total Fe(II+III) by the light-absorption ratio variation approach (LARVA). Results indicated that AA, of the Fe-RTMPF solution is linear at 568 and 641.5 nm at the range between 0 and 100 ng/mL Fe. The limit of detection (3 sigma) of Fe is only 2 ng/mL. This method was applied to analysis of several samples such as natural waters, cigarette ash, and urine with satisfactory results.