Synergistic Extraction of Manganese(II) and Iron(II) with Monothiothenoyltrifluoroacetone and 1,10-Phenanthroline

Abstract

A simple and accurate HPLC method was developed for the determination of pheophytinatoiron(III) chloride (PheoFeCl) prepared by the replacement of magnesium(II) in chlorophyll [pheophytinatomagnesium(II)] with iron( III). The good separation of PheoFeCl was obtained by using a stationary phase of C18 chemically bonded to silica gel and a mobile phase of acetone-acetonitrile (50:50, v/v). A tailing of the PheoFeCl peak due to the dissociation of ion pairs was improved by addition of tetramethylammonium chloride to the mobile phase. The spectrophotometric method was also used for a comparison to the HPLC method. For the synthetic samples prepared by mixing (pheophytinato a)iron(III) chloride [(Pheo-a)FeCl] and (pheophytinato b)iron(III) chloride [(Pheo-b)FeCl], analytical values by the spectrophotometric method were extremely high compared to those by the HPLC method because of interferences from the absorption of coexistent pigments. In the proposed HPLC method, (Pheo-a)FeCl and (Pheo-b)FeCl could be determined in the concentration range of 0.025-30μg cm-3and 0.06- 30μg cm-3with relative standard deviations (n=10) of 6.2% and 18%, respectively.