Photometric Determination of Manganese in 3 Traditional Chinese Medicines (Astragalus Membranaceus,Safflower and Leaves of Artemisia Argyi)

Samples of the 3 TCM′s were digested with conc.HNO3 and evaporated to near dryness with conc.HClO4 to obtain clear and transparent solution.An aliquot of sample solution was taken and manganese was determined by the diantipyryl benzenevinylmethane (DABVM) photometric method.Manganese(Ⅱ) in the solution was first oxidized to Mn(Ⅳ) in an alkali medium by air and dissolved oxygen and by heating in a boiling water bath for 5 min,and then reacted with DABVM in H3PO4 medium (2+1).The absorbance of the colored complex formed was measured at 540 nm.Linear relationship between values of absorbance and mass concentration of Mn(Ⅱ) was obtained in the range of 0.5-5.0 mg·L-1.Recovery was tested by addition of standard manganese solutions to samples of the 3 medicines and determined by the proposed method,results of recovery were found in the range of 102.6%-104.0%,with values of RSD′s (n=5) less than 4.5%