Spectrophotometric Determination of Iron in 4 Varieties of Mangoes

The sample of each of the 4 varieties of mangoes, i.e. Heart-shaped mango, Tainong mango, Jinhuang mango and Golden mango was digested with a mixed acid of perchloric acid and nitric acid (1+4). The solution was evaporated to near dryness, and the residue was taken up with water and diluted to 25 mL with water. An aliquot of 1.50 mL of the solution was taken, and 1.00 mL of 100 g·L-1 NH2OH·HCl solution was added to reduce Fe(Ⅲ) ion to Fe(Ⅱ) ion, which was the determined by spectrophotometry. Iron in sample solution was determined by spectrophotometry based on the formation of blue color by the reaction between Fe2+ ion and potassium ferricyanide. Linear relationship between values of absorbance and mass concentration of iron was obtained in the range of 0.04-10.09 mg·L-1, with detection limit (3S/N) of 0.02 mg·L-1. Values of recovery found by standard addition method were in the range of 98.7%-100%, and values of RSD′s (n=6) found were less than 0.60%. Iron contents of the 4 varieties of mangoes were found successively increased from Heart-shaped mango, Jinhuang mango, Golden mango to Tainong mango.