碘阻抑结晶紫褪色动力学光度法测定微量碘

Kinetic Spectrophotometric Determination of Microamounts of Iodine Based on InhibitoryEffect on Decoloration Reaction of CrystaI Vi-olet

在弱酸性介质中，微量Ｉ￣－对ＮａＩＯ＿４氧化结晶紫褪色的反应具有显著的阻抑作用，以此反应为指示反应提出了测定微量碘的动力学光度分析法。反应的最佳实验条件为：２５ｍＬ试液中含ｐＨ５．７～６．５的磷酸盐缓冲溶液５ｍＬ、５．０×１０￣（－４）ｍｏｌ／Ｌ结晶紫１．０ｍＬ、１．０×１０￣（－２）ｍｏｌ／ＬＮａＩＯ＿４０．８ｍＬ、８０℃水浴加热１８ｍｉｎ。方法的检测限为３．８×１０￣（－６）／Ｌ，线性范围是０．００８～０．２０ｍｇ／Ｌ，简便快速，重现性佳，直接用于食盐分析有满意的结果。

A new and sensitive kinetic method hasbeen developed for the spectrophotometric de-termination of microamounts of iodine,basedon the inhibitorv action of iodide ion on thecolor fading reaction of crystal violet(C.I.42555)oxided by sodium periodate in phos-phate buffer medium at pH 5.7～6.5. The op-timum conditions of the reaction are as fol-lows : iodide ion solution containing less than5. 0μg is added in to a mixture of 5mL of 0.5mol/L phosphate buffer,1.0mL of 5. 0×10￣(-4)mol/L crystal violet and 0. 8mL of 1.0×10￣(-2)mol/L NaIO_4.The so1ution is finally dilutedto 25mL and heated for 18min in a water bathat 80℃.The detection limit is 3.8 × 10￣(-6)g/L,and the calibration curve for iodine is linear inthe range of 0.008～0.20mg/L. The method isselective and very simple,and has been appliedto the determination ohodine in table salt withsatisfactorv results.