EVALUATION OF HIBISCUS AND ROSE FLOWER EXTRACTS AS ECO FRIENDLY NATURAL PH INDICATORS FOR ACID–BASE TITRIMETRIC ANALYSIS
DOI:
https://doi.org/10.65009/3cexr250Keywords:
Natural indicators, Hibiscus rosa-sinensis, Rose extract, Anthocyanins, Acid–base titration, UV–Vis spectroscopy, Green chemistry.,,Abstract
The widespread use of synthetic acid–base indicators in chemical laboratories has raised
concerns regarding toxicity, environmental pollution, and disposal hazards. In recent years, increasing
emphasis on green chemistry has encouraged researchers to identify sustainable alternatives derived from
natural sources. In the present work, aqueous extracts of Hibiscus rosa-sinensis and Rosa rubiginosa
flowers were investigated as
eco-friendly natural pH indicators for acid–base titrimetric analysis. Flower extracts were prepared using
hot water extraction methods and characterized through acid–base titration and UV–Visible spectroscopic
analysis. The prepared extracts showed sharp color transitions in acidic and alkaline media. Hibiscus
extract exhibited a pink coloration in acidic medium and pale yellow coloration in alkaline medium,
whereas rose extract showed red to greenish transitions. UV–Visible spectroscopy revealed maximum
absorbance at 580 nm due to anthocyanin pigments responsible for pH sensitivity. Experimental results
demonstrated endpoint detection comparable to synthetic indicators such as phenolphthalein and methyl
red. Furthermore, natural indicators were found to be inexpensive, biodegradable, non-toxic, and
environmentally friendly. The findings indicate that flower-based natural indicators can effectively replace
synthetic indicators in laboratory analysis and educational chemistry applications.
References
D. Tzur and E. Kirowa-Eisner, “Consecutive titrations under non-equilibrium conditions,”
Analytica Chimica Acta, vol. 355, no. 1, pp. 85–93, 1997.
M. A. K. Pathan and M. Farooqui, “Analytical applications of plant extract as natural pH indicator: A
review,”
B. Bhuvaneshwari et al., “Natural dyes as acid-base indicators from beta vulgaris,” Research
Journal of Pharmacognosy and Phytochemistry, vol. 7, no. 2, p. 65, 2015.
P. S. Vankar and D. Bajpai, “Rose anthocyanins as acid-base indicators,” EJEAFChe, vol. 9,
no. 5, pp. 875–884, 2010.
S. Sharma, A. Babu, and V. Saxena, “Extraction and evaluation of some natural flower pigments,”
Journal of Population Therapeutics and Clinical Pharmacology, vol. 32, no. 10, pp. 1703–1712, 2025.
S. Rahmawati et al., “Evaluating Torenia fournieri flower extract as a natural acid-base titration
indicator,”
International Journal of Design & Nature and Ecodynamics, vol. 19, no. 2, pp. 497–503, 2024.
B. Wiyantoko and Astuti, “Butterfly Pea extract as indicator of acid-base titration,” Indonesian
Journal of Chemical Analysis, vol. 3, no. 1, pp. 22–32, 2020.
M. U. Ghurde and P. S. Aswar, “An investigation of Antigonon leptopus as natural pH indicator,”
International Journal of Science and Research, vol. 14, no. 7, pp. 456–459, 2025.
