Determination of manganese in some medicinal plants and their infusions by a catalytic spectrophotometric method.
The catalytic effect of manganese (II) on the oxidation of the azo dye 3-Methyl-6-(2-hydroxyethoxy)-2-[2-methoxy-4-N (N, N diethylamino) phenylazo] benzothiazolium methylsulphate, with potassium periodate in the presence of 1,10-phenanthroline in weakly acidic media was studied. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 560 nm. Under the optimum conditions (4 x 10(-5) mol dm(-3) azo dye, 4 x 10(-4) mol dm(-3) potassium periodate, 1 x 10(-4) mol dm(-3) 1,10-phenanthroline, 0.1 mol dm(-3) buffer--pH 3.0, 70 degrees C, 8 min) manganese (II) in the range 0.1-5 ng cm(-3) could be determined by the fixed-time method with a detection limit of 0.035 ng cm(-3). The developed method is highly sensitive, selective, and simple. The method was applied successfully to the determination of total manganese in some medicinal plants and to analyse their infusions for trace amounts of total manganese and free manganese (II) ions without separation.
Mutaftchiev
Konstantin
K
Department of Chemistry and Biochemistry, Higher Medical Institute 5800 Pleven, Bulgaria. konlubmut@yahoo.com
D001391:Azo Compounds / Q000032:analysis / Q000737:chemistry; D002384:Catalysis; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008345:Manganese / Q000032:analysis* / Q000737:chemistry; D010084:Oxidation-Reduction; D010504:Periodic Acid / Q000737:chemistry; D010618:Phenanthrolines / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry*; D017680:Potassium Compounds / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods*
D001391:Azo Compounds; D007477:Ions; D010618:Phenanthrolines; D017680:Potassium Compounds; D010504:Periodic Acid; D008345:Manganese; C037192:potassium periodate; C025205:1,10-phenanthroline