A novel simple, sensitive, rapid, direct, and spectrophotometry-based procedure was investigated to determine Th(IV) at trace amounts. The new method is based on Th(IV) chelation with 3,6-dichloro-2,5-dihy-droxy-l,4-benzoquinone (DDBQ). The reagent reacts with Th(IV) in 0.1 M HCl to form an orange 1:2 complex. The stability constant value is 6.62 × 104 for the Th(IV) complex. The Th(IV)-DDBQ obtained shows one peak with a maximum at about 346 nm. The chelate forms immediately and the absorbance remains stable for over 24 h. Beer''s law was obeyed in the concentration range 0-10 μg mL-1. The molar absorptivity and Sandell''s sensitivity were 4.4 × 104 L mol-1 cm-1 and 0.0053 μg cm-2, respectively. Different analytical param-eters were tested in detail. Interfering ion (cations and anions) effects were tested. Methods for Th(IV) determi-nation by second and third-derivative spectrophotometry were also introduced at about 344 and 341 nm, respec-tively. These two derivative orders offer the feature of sensitivity without the necessity for solvent extraction, heating, or pre-concentration steps. Finally, the methods were successfully utilized for Th(IV) determination in monazite, environmental water, and wastewater samples.
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机译：研究了一种新颖，简单，灵敏，快速，直接和基于分光光度法的方法来测定痕量Th（IV）。新方法基于与3,6-dichloro-2,5-dihy-droxy-1,4-苯醌（DDBQ）的Th（IV）螯合。该试剂在0.1 M HCl中与Th（IV）反应形成橙色的1：2络合物。 Th（IV）配合物的稳定常数值为6.62×104。所获得的Th（IV）-DDBQ显示出一个峰，该峰的最大值在约346nm处。螯合物立即形成，吸光度保持稳定超过24小时。在0-10μgmL-1的浓度范围内遵守比尔定律。摩尔吸收率和Sandell的灵敏度分别为4.4×104 L mol-1 cm-1和0.0053μgcm-2。详细测试了不同的分析参数。测试了干扰离子（阳离子和阴离子）的作用。还分别介绍了通过二阶和三阶分光光度法测定Th（IV）的方法。这两个导数阶提供了灵敏度的特征，而无需进行溶剂萃取，加热或预浓缩步骤。最后，这些方法已成功用于独居石，环境水和废水样品中Th（IV）的测定。
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