New, sensitive, and reliable spectroscopic methods were constructed for the fast determination of the anthelmintic drug mebendazole. The methods depended on the reaction of the amino group in mebendazole with eosin in acidic medium forming an ion pair complex. The first method, Method I, relied on quenching of the native fluorescence of eosin after reaction with mebendazole at pH 3.7 using acetate buffer. Fluorescence quenching was measured at 538 nm after excitation at 518 nm. This method showed a linear response over the concentration range 5.0–20.0 μg/ml. The second method, Method II, was based on measuring the absorbance of the formed complex at 554 nm; the method showed good linearity from 7.0 to 22.0 μg/ml. Different parameters that influenced the formation of the reaction product were carefully investigated to reach the optimized conditions. A comparison between the proposed methods and a previous spectrophotometric method was carried out and there was no significant difference between them. The methods could be applied successfully to determine mebendazole in its tablet form. Moreover, the methods used water as diluting solvent, which made them compatible with the ‘green’ analytical chemistry principles. No organic solvents were used throughout the study.

中文翻译：

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曙红用于绿色光谱法测定甲苯达唑的用途。

构建了一种新的，灵敏且可靠的光谱方法，用于快速测定驱虫药甲苯达唑。该方法取决于甲苯咪唑中的氨基与曙红在酸性介质中形成离子对络合物的反应。第一种方法，方法I，是使用乙酸缓冲液在pH 3.7下与甲苯咪唑反应后，对曙红的天然荧光进行猝灭。在518nm激发后在538nm测量荧光猝灭。该方法在5.0-20.0μg/ ml的浓度范围内显示线性响应。第二种方法，方法II，是基于在554 nm下测量所形成的络合物的吸光度。该方法在7.0至22.0μg/ ml之间显示出良好的线性。仔细研究了影响反应产物形成的不同参数，以达到最佳条件。所提出的方法与先前的分光光度法进行了比较，两者之间没有显着差异。该方法可以成功地用于测定片剂形式的甲苯达唑。此外，该方法使用水作为稀释溶剂，这使其与“绿色”分析化学原理兼容。在整个研究中未使用有机溶剂。