Revolutionizing Indigo-Dyed Fabric Identification: A Novel Sulfonation Approach for Authenticity and Quality Assurance

This study explores a novel sulfonation method for analyzing blue-dyed fabrics containing reactive, direct and indigo dyes. The proposed method accurately distinguishes indigo fabrics by converting indigo blue into indigo carmine using concentrated H2SO4, resulting in distinct spectral analysis through UV-Visible spectrophotometry. Generally, UV-Visible spectroscopy shows absorption peak characteristics influenced by analyte and environmental properties, leading to broadening and wavelength shifts. Therefore, statistical analysis of peak characteristics, including center, centroid, Full Width at Half Maximum (FWHM), height and L/R ratio, was performed on the obtained spectra to facilitate comprehensive quality evaluation of indigo-dyed fabrics. The proposed method demonstrated good precision and accuracy, with %RSD values indicating excellent repeatability and reproducibility, contingent on consistent sample preparation, narrow analyte peaks and minimized background signals. Furthermore, this method was applied to analyze the collected indigo-dyed fabrics from Sakon Nakhon Province, revealing the center value (611.79 nm) as a precise marker for indigo dye, with a narrow control range (607.02 - 616.56 nm) and a low coefficient of variation (CV) of 0.26 %. Moreover, centroid, L/R ratio and FWHM significantly contributed to fabric classification and quality assessment. This research offers valuable insights to improve indigo fabric production in Sakon Nakhon Province, leading to more reliable authentication and quality control of the natural indigo-dyed industry.