高温热水解-催化分光光度法测定植物样品中的痕量碘

建立了测定植物中痕量碘的高温热水解-催化分光光度法。设计了预处理程序以使植物样品能够稳定、彻底地进行热水解。通过正交实验优化了样品预处理的热水解参数:样品质量0.5g、氧气流量100mL/min、吸收液的NaOH浓度0.2mol/L、温度1100℃和热水解时间20min。为提高催化分光光度法测定吸收液中痕量碘的灵敏度,碘催化砷铈氧化还原反应的条件优化为:反应温度45℃、反应时间35min。该方法的检测限和定量下限分别为0.3ng/g和0.9ng/g,满足植物样品中痕量碘的分析要求。对国家标准植物样品的分析结果表明该方法准确度高、精密度好。由于使用的仪器都很常用、便宜,并具有测试费用低廉,检测限低、准确度和精密度高等优点,该方法易于推广使用,适合于植物样品碘含量的日常分析。

Determination of Trace Iodine in Vegetable Samples by Pyrohydrolysis for Preparation and Catalytic Spectrophotometry for Measurement

The pyrohydrolysis was applied to vegetable sample digestion and further determination of iodine by catalytic spectrophotometry(CS).The pretreatment program of pyrohydrolysis was designed to decompose the vegetable samples steadily and completely.The conditions of pyrohydrolysis for sample preparation optimized through orthogonal experiment are presented as follows: 0.5 g vegetable sample,a temperature of 1100℃,20 minutes of pyrohydrolysis,100 mL/min of oxygen flux and 0.2 mol/L NaOH of absorption solution.In order to enhance the sensitivity of the method,the conditions of CS were optimized as follows: reaction temperature 45℃ and reaction time 35 minutes.The limit of detection and quantification were 0.3 ng/g and 0.9 ng/g,respectively,hence it can be applied to determining trace iodine in vegetable samples.Precision and accuracy were evaluated by the analysis of Chinese vegetable sample reference materials.Owing to the low cost of instruments and analysis,low limit of detection,high accuracy and precision,the pyrohydrolysis-CS method is very suitable for the daily analysis of the iodine contents in vegetable samples.