Activated carbon from green walnut shells as the adsorbent for the solid-phase extraction of indigo carmine from food and textiles

Abstract

Activated carbon from green walnut shells was synthesized; characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX); and used as an adsorbent for the separation and preconcentration of indigo carmine. The pH, adsorbent mass, sample volume, foreign ion effect, eluent type, and eluent volume were optimized. The preconcentration factor was 20.0 and the enrichment factor was 19.68. The developed SPE method provided a limit of detection of 40.8 µg L⁻¹ and limit of quantification of 136.1 µg L⁻¹. The analyte recoveries were from 92 to 102%. The intra-day and inter-day relative standard deviations were 3.2% and 3.8%. The protocol was employed for the separation, preconcentration, and spectrophotometric determination of indigo carmine in water, candies, hair dyes, edible cake decorations, fruit juices, and textiles.

Keywords:

• Activated carbon
• İndigo carmine
• solid phase extraction (SPE)
• spectrophotometry

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that influenced the work reported in this article.