6'-(indolin-1-yl)-1-(4-methoxybenzyl)-3,3-dimethylspiro[indoline-2,3'-naphtho[2,1-b][1,4]oxazine] (SPO), a novel colorimetric probe in a spirooxazine class, was successfully synthesized. Its molecular structure was confirmed by the single crystal and spectroscopic analyses. Upon UV activation, SPO in a 1,4-dioxane solution possessed superior selectivity and sensitivity for colorimetric detection of CH₃Hg⁺ over other cations, including Hg²⁺. The results from the absorption study showed that the mixtures of SPO and Hg²⁺ or CH₃Hg⁺ exhibited a new absorption band at 590 nm. This indicates the structural isomerization of SPO into an open-form merocyanine which acts as a ligand to form an SPO-Hg²⁺ or SPO-CH₃Hg⁺ complex. The stoichiometric ratio of SPO to each mercuric cation in the complexes was determined using Job’s method and the results suggested that the complexes were formed at a 1:1 mole ratio. The detection limit of Hg²⁺ and CH₃Hg⁺ in 1,4-dioxane was investigated and the results showed the values at nM level (152 nM for Hg²⁺ and 150 nM for CH₃Hg⁺). Moreover, the test strips coated with SPO were also demonstrated to provide a practically highly sensitive detection of CH₃Hg⁺ in mixed 1,4-dioxane:water solutions.

6'-（吲哚啉-1-基）-1-（4-甲氧基苄基）-3,3-二甲基螺[吲哚啉-2,3'-萘[2,1- b ] [1,4]恶嗪]（SPO）成功合成了螺恶嗪类的新型比色探针。通过单晶和光谱分析证实了其分子结构。在UV活化后，1,4-二恶烷溶液中的SPO具有比其他阳离子（包括Hg ^2+）更高的选择性和灵敏度，可比色检测CH ₃ Hg ⁺。吸收研究的结果表明，SPO和Hg ²⁺或CH ₃ Hg ⁺的混合物在590 nm处表现出新的吸收带。这表明SPO在结构上异构化成开放型的花菁，其充当配体以形成SPO -Hg ²⁺或SPO -CH ₃ Hg ⁺络合物。使用Job方法确定了配合物中SPO与每种汞阳离子的化学计量比，结果表明配合物的摩尔比为1：1。研究了1,4-二恶烷中Hg ²⁺和CH ₃ Hg ⁺的检出限，结果显示了nM值（Hg ²⁺为152 nM，CH ₃ Hg为150 nM⁺）。此外，还证明了涂有SPO的测试条可提供一种实用的高灵敏度检测方法，用于混合1,4-二恶烷：水溶液中的CH ₃ Hg ⁺。