用赤霉素作还原剂钼蓝法测定茶叶中痕量砷

SPECTROPHOTOMETRIC DETERMINATION OF TRACE ARSENICUM IN TEA BY MOLYBDENUM BLUE METHOD USING GIBBERELLIN AS A NEW REDUCING AGENT

用赤霉素作新的还原剂，对砷钼杂多酸的还原反应进行了研究。在０．８４ｍｏｌ／ＬＨＣｌ介质中，赤霉素能将砷钼杂多酸还原成十分稳定的砷钼杂多蓝，其最大吸收波长为８３５ｎｍ，表观摩尔吸光系数为２．６４×１０４Ｌ·ｍｏｌ－１·ｃｍ－１。砷浓度在０～１．２０ｍｇ／Ｌ范围内符合Ｂｅｅｒ定律。该法选择性好，灵敏度高。可用于茶叶中痕量砷的测定。

Gibberellin is introduced as a new reducing agent and is systematically studied on arsenicum molybdenum acid reduction.In the 0.84mol/L HCl medium the As-Mo heteropoly acid can be reducied into very stable As-Mo heteropoly blue by gibberellin.The maxium absorption wave length is 835 nm.The molar absorption coefficient is 2.64×104 L·mol-1·cm-1.It conforms the Beers law when the concentration of As is 0～30μg/25ml.This is a highly selective and sensitive method.It is satisfied when adopted in determining arsenicum in tea.