ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Exploring natural indicators: aronia berries and turmeric as eco-friendly and cost-effective alternatives for acid–base titrations

Ivona Sofronievska, Marinela Cvetanoska, and Jasmina Petreska Stanoeva

Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Ss. Cyril and Methodius University in Skopje, Skopje, North Macedonia

E-mail: marinela.cvetanoska@pmf.ukim.mk

Received: 16 January 2025  Accepted: 29 March 2025

Abstract:

This study investigates the potential of aronia (rich in cyanidins) and turmeric (containing curcumin) extracts as natural indicators for acid–base titrations. The extracts were characterized using HPLC/DAD/ESI-MSⁿ. For the first time, this study explores the use of natural indicators in the titrations of polyprotic acids and bases. Aronia extract exhibited a color change from pink (acidic) to turquoise (basic), with absorption maxima at 515 and 610 nm, respectively. It was effective for titrations involving weak bases with strong acids and polyprotic acids and bases, with relative errors around 0.5%. It was especially effective for determining the second end point in Na₂CO₃ titrations and the first end point in H₃PO₄ titrations, with relative errors around 1%. Turmeric extract demonstrated a yellow-to-orange color transition, with absorption maxima at 425 (acidic) and 460 nm (basic). It was effective for titrations of weak acids with strong bases and the first end point in Na₂CO₃ titrations, with errors under 1%. Turmeric was also suitable for the second end point in H₃PO₄ titrations, with a relative error around 2%. Both natural indicators showed promising results compared to synthetic indicators. Aronia extract can be used in acid–base titrations instead of methyl red, while turmeric extract can replace phenolphthalein.

Graphical Abstract

Keywords: Arbuscular mycorrhiza; Jasmonic acid; Natural Products; Plant Materials; Potassium; Spectrophotometry; Natural indicators; Titrations; Analytical chemistry; Turmeric; Aronia

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04049-w

Chemical Papers 79 (6) 3977–3984 (2025)