Simple Spectrophotometric Determination of Indigo in natural samples.

• DOI: https://doi.org/10.22533/at.ed.317542517034

• Palavras-chave: Indigo, spectrophotometric analysis, natural dyes, analytical chemistry.

• Keywords: Indigo, spectrophotometric analysis, natural dyes, analytical chemistry.

• Abstract: A simple and rapid spectrophotometric method for the determination of indigo is presented. This method is based on the formation of the N,N'-diacetyl derivative of indigo, which allows for a more stable and soluble product suitable for analysis. The method follows Beer’s law in the concentration range of 1–20 µg mL⁻¹ at a maximum absorption of 614 nm. The developed technique has been successfully applied to the quantification of indigo in natural samples, demonstrating high sensitivity, reproducibility, and accuracy. Compared to traditional methods such as HPLC and UV-Vis, this approach offers a more straightforward and cost-effective alternative while maintaining high analytical performance. Additionally, the proposed method avoids issues related to the low solubility of indigo in various solvents, providing a more efficient derivatization process that enhances measurement accuracy. A comparative study with existing methodologies highlights the advantages of the N,N'-diacetyl derivative approach, particularly in terms of sample preparation, stability, and signal reliability. The results obtained confirm that this method can be reliably used for routine analysis of indigo in different natural matrices. Furthermore, statistical validation of the method ensures its applicability in industrial and research settings.