Investigation and Comparative Study of Newly Synthesized Azo Compounds as Acid-Base Indicators and Indicator Strips

Abstract

In this study, the characterization and application of various synthesized azo compounds were comprehensively investigated. Spectroscopic techniques, including FT-IR, 1H-NMR, and 13C-NMR, were initially employed to confirm the chemical structure of five azo derivatives (A1-A5). These compounds were subsequently utilized to fabricate pH or acid-base indicator paper. The colorimetric responses of the five different azo derivatives were extensively evaluated across a range of pH media. The results demonstrated that each azo-based pH indicator paper exhibited two distinct color transitions (color shifts—from yellow to red or orange—upon conducting buffer solutions ranging from pH 2 to pH 12) when the medium shifted from acidic to basic conditions, or vice versa. Additionally, the azo compound solutions were evaluated against standard reference indicators to assess their performance as acid-base indicators. The findings demonstrated that the proposed A1-A5 indicators accurately detected titration endpoints with high precision, exhibited potential as viable alternatives to conventional reference indicators such as phenolphthalein and methyl red. During acid-base titration, no statistically significant differences were observed in the required titrant volumes when using the A1–A5 indicators compared to standard reference indicators. Specifically, p-values of 0.311 (HCl vs. NaOH) and 0.265 (CH₃COOH vs. NaOH) confirmed equivalence in endpoint detection. The proposed indicators can be intensively utilized for educational purposes and suggested for monitoring acidity or alkalinity of fields, including environmental, industrial and biological fields.