Nacapricha D, Muangkaew S, Ratanawimarnwong N, Shiowatana J, Grudpan K
Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
Analyst. 2001 Jan;126(1):121-6. doi: 10.1039/b007131p.
This paper describes the use of flow injection (FI) techniques for the determination of iodine in urine, based on the catalytic effect of iodide in the redox reaction between Ce(IV) and As(III). The proposed procedures minimize errors in the conventional batch method arising from the reading of absorbance at a fixed time after addition of Ce(IV) reagent. Two FI systems, for the continuous and stopped modes of operation were assembled. In the continuous-FI system, a thermostated bath was used to increase the sensitivity. However this is not necessary for the stopped-FI system. The two systems are comparable in terms of sensitivity, sample throughput and detection limit. The continuous-FI and the stopped-FI exhibited detection limits (3 sigma) of 2.3 and 3 micrograms I l-1 respectively. Both systems have equal sample throughputs of 35 samples h-1. Calibration plots for both techniques are linear. The FI procedures provide very short analysis times compared to the batch procedure. Using the linear regression test, there is no significant difference between the results from the four methods, i.e., continuous-FI, stopped-FI, conventional method and ICP-MS. The proposed methods are readily applicable for automation and can be an alternative to the conventional procedure for the survey of the iodine deficiency disorder. A condition for sample digestion is also proposed to reduce the amount of chloric acid required for complete digestion. Kinetic information of the reaction can also be obtained from the stopped flow mode.
本文描述了基于碘化物在铈（IV）与砷（III）之间氧化还原反应中的催化作用，采用流动注射（FI）技术测定尿液中的碘。所提出的方法将传统分批法中因在加入铈（IV）试剂后固定时间读取吸光度而产生的误差降至最低。组装了两种用于连续操作模式和停流操作模式的FI系统。在连续流动注射系统中，使用恒温浴提高灵敏度。然而，对于停流注射系统来说这并非必要。这两种系统在灵敏度、样品通量和检测限方面具有可比性。连续流动注射系统和停流注射系统的检测限（3σ）分别为2.3和3微克碘/升。两种系统的样品通量均为每小时35个样品。两种技术的校准曲线均呈线性。与分批法相比，流动注射法的分析时间非常短。通过线性回归测试，连续流动注射法、停流注射法、传统方法和电感耦合等离子体质谱法这四种方法的结果之间没有显著差异。所提出的方法易于实现自动化，可作为碘缺乏病调查中传统方法的替代方法。还提出了样品消解的条件，以减少完全消解所需的氯酸量。反应的动力学信息也可从停流模式中获得。
