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Spectrophotometric Determination of Manganese in Cooking Wine Samples by Oxidation of Chromotrope 2B

SHA Ou,CHEN Li,MA Wei-xing   

  1. 1. School of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005, China;
    2. Analysis and Test Center, Jiangsu Marine Resources Development Research Institute, Lianyungang 222001, China
  • Online:2013-06-25 Published:2013-06-17

Abstract:

A new spectrophotometric method for determining manganese in cooking wine was established by oxidation of
chromotrope 2B. In the presence of sodium bismuthate, all low-valent Mn ions in samples were oxidized to form to Mn (Ⅶ), which
oxided chromotrope 2B at room temperature in sulfuric acid medium resulting in fading. The most considerable reduction in the
absorbance at 515 nm was observed, which was directly proportional to Mn (Ⅶ) concentration. The absorbance obeyed Beer’s law
in the Mn (Ⅶ) concentration range of 0.05 to 5.0 μg/mL with an apparent molar absorption coefficient of 2.05 × 104 L/(mol•cm).
The recovery of the developed method for spiked samples of commercial liquor and cooking wine ranged between 98.5% and
101.9%, and the results obtained were consistent with those reported with ICP-AES.

Key words: manganese, spectrophotometry, chromotrope 2B, wine