Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Al-Azhar University, Assiut Branch, Assiut 71524, Egypt.
College of Food Engineering, Bio-Nanotechnology Research Institute, Ludong University, Yantai, 264025, Shandong, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2025 Jan 15;325:125073. doi: 10.1016/j.saa.2024.125073. Epub 2024 Sep 6.
Indigo carmine (IN-CR) is a synthetic blue dye widely used as a coloring agent in various food and beverage products. It is recognized for its ability to enhance the visual appeal, hue, and consistency of food products. However, recent studies have raised concerns about the potential health risks associated with this substance. Therefore, a highly sensitive analytical tool is required for the trace determination of IN-CR in food products. This study describes the spectral characteristics of micellar-enhanced fluorescence of europium (III)-doxycycline complex and its employment as a sensor for the development of a highly sensitive fluorimetric assay for the trace determination of IN-CR. The complex was formed in an alkaline medium containing hydrogen peroxide and encapsulated into cetyltrimethylammonium bromide micelles. This micellar-encapsulated complex exhibited significantly enhanced fluorescence at a wavelength of 613.5 nm, overlapping with the maximum absorption peak of IN-CR at 610 nm. This inner-filter effect phenomenon resulted in IN-CR's concentration-dependent quenching of the complex's fluorescence. The fluorescence quenching of the complex by inner-filter effect of IN-CR was adopted in the development of a highly sensitive fluorimetric assay for IN-CR. The conditions of the assay were refined, and the optimum procedures were established. The assay was validated for its performance characteristics, and all the validation criteria were met. The assay displayed linearity within the IN-CR concentration range of 100-1250 ng mL, with a limit of detection at 41.2 ng mL. Importantly, the assay exhibited no interference from other substances commonly used as food additives. The recoveries ranged from 99.11 % to 101.57 %, with relative standard deviations ranging from 1.34 % to 1.89 %.The assay was successfully applied to the determination of IN-CR in commercial syrup products, and the recoveries ranged from 93.5 % to 106.32 % with relative standard deviations ≤4.72 %, confirming the reliability of the assay. The proposed assay provides some key advantages, including a novel application of the europium (III)-doxycycline complex as a fluorescence sensor for the determination of IN-CR in real syrups innovative, high sensitivity and selectivity, simplicity of analysis procedures, time-saving of entire analysis protocol. In conclusion, the assay serves as a valuable tool for quantifying IN-CR in food products, facilitating the assessment of both food quality and safety.
靛红胭脂红（IN-CR）是一种合成蓝色染料，广泛用作各种食品和饮料产品的着色剂。它以增强食品产品的视觉吸引力、色调和一致性而闻名。然而，最近的研究引起了人们对与这种物质相关的潜在健康风险的关注。因此，需要一种高度敏感的分析工具来痕量测定食品产品中的 IN-CR。本研究描述了铕（III）-强力霉素配合物胶束增强荧光的光谱特征，并将其用作开发痕量测定 IN-CR 的高灵敏度荧光分析方法的传感器。该配合物在含有过氧化氢的碱性介质中形成，并被包裹在十六烷基三甲基溴化铵胶束中。这种胶束封装的配合物在 613.5nm 处表现出明显增强的荧光，与 IN-CR 的最大吸收峰 610nm 重叠。这种内滤效应现象导致 IN-CR 的浓度依赖性猝灭配合物的荧光。通过 IN-CR 的内滤效应，采用荧光猝灭法开发了一种高灵敏度的 IN-CR 荧光分析方法。对测定方法的条件进行了优化，并确定了最佳程序。对测定方法的性能特征进行了验证，所有验证标准均符合要求。该测定方法在 IN-CR 浓度范围为 100-1250ng mL 内呈线性，检测限为 41.2ng mL。重要的是，该测定方法不受常用食品添加剂的其他物质的干扰。回收率在 99.11%至 101.57%之间，相对标准偏差在 1.34%至 1.89%之间。该测定方法成功应用于商业糖浆产品中 IN-CR 的测定，回收率在 93.5%至 106.32%之间，相对标准偏差≤4.72%，证实了该测定方法的可靠性。所提出的测定方法具有一些关键优势，包括将铕（III）-强力霉素配合物作为荧光传感器用于测定真实糖浆中 IN-CR 的新颖应用；创新性、高灵敏度和选择性；分析程序简单；整个分析方案省时。总之，该测定方法为定量测定食品中的 IN-CR 提供了一种有价值的工具，有助于评估食品质量和安全性。
