Novel eco-friendly acid-base indicators from innovative plant-based sources: Water-based extraction and applications in titration

作     者：Sinélcio Samuel Taualia Ali Achira Germildo Juvenal Muchave Célio Matias Airone Macalia Neuana Fernando Neuana Ana Paula Capelezzo Raimundo Rafael Gamela Domingos Lusitâneo Pier Macuvele 

作者机构：Department of Science Engineering Technology and Mathematics Center for Studies in Science and Technology (NECET) University of Rovuma Lichinga Niassa Mozambique Instituto de Química e Biotecnologia (IQB/UFAL) Universidade Federal de Alagoas Maceió Brazil Research Department Open University ISCED Rua Paiva Couceiro 148/07 Macuti Beira Mozambique Green Technologies Laboratory Escola de Química Universidade Federal do Rio de Janeiro Rio de Janeiro Rio de Janeiro 21941-909 Brazil Programa de Pós-graduação em Ciência e Engenharia de Materiais-PPGCEM Universidade Federal de Amazonas Manaus Amazonas Brazil Chemical Department Engineering Community University of Chapecó Region (Unochapecó) Chapecó SC Brazil Division of Agriculture High Polytechnique Institute of Gaza (ISPG) Lionde Chòkwé Gaza CP 1204 Mozambique Graduate Program in Chemical Enginering Santa Catarina Federal University (UFSC) Florianópolis SC Brazil 

出 版 物：《Next Research》 

年 卷 期：2025年第2卷第1期

主　　题：Plant extracts Eco-friendly acid-base indicators Titration Environment sustainability Green chemistry 

摘      要：Researching new plants as potential green indicators marks a meaningful step toward sustainability in analytical chemistry. This study aimed to identify plants with viable applications as eco-friendly indicators in acid-base titration. For this purpose, ten plants were selected based on distinct color properties, namely Euphorbia cotinifolia, Acalypha wilkesiana, Alternanthera brasiliana, Mirabilis jalapa, Datura metel, Euphorbia milii, Jacaranda mimosifolia, Luffa aegyptiaca, Senna didymobotrya , and Canna indica . Aqueous extracts were obtained by maceration, and their performance as acid-base indicators was evaluated and compared with synthetic indicators phenolphthalein and bromothymol blue. The results demonstrated that six of the ten extracts— Euphorbia cotinifolia, Acalypha wilkesiana, Alternanthera brasiliana, Mirabilis jalapa, Datura metel , and Euphorbia milii —were effective in producing visible color changes across pH levels. Notably, the extracts of Alternanthera brasiliana, Acalypha wilkesiana , and Euphorbia milii exhibited highly perceptible color transitions at different pH values, with equivalence points that closely aligned with those obtained by synthetic indicators in all titration types. The titrant volume using natural acid-base indicators was between 4.21 ± 0.06 mL (CH 3 COOH/NH 4 OH) and 7.60 ± 0.44 mL (HCl/NH 4 OH). Statistical analysis revealed significant differences in titrant excesses between these natural extracts and synthetic indicators, with Acalypha wilkesiana and Alternanthera brasiliana achieving up to 15×10 -5 lower HCl excess, indicating their sensitive and precise response in color transition, reinforcing their potential as reliable acid-base indicators. These findings validate the ecological and practical advantages of these plant-based indicators, which are locally available, cost-effective, and stable throughout titrations. As such, they represent a promising and sustainable alternative for laboratories and industries, with