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Updated: Sep 18, 2026

Facile Preparation of 4-Substituted Quinazoline Derivatives
Published on: February 15, 2016
4-Sulfophenyl diazonium salt, a new, precise and selective alternative to the Folin-Ciocalteu method for the
Emilio Piña Betancourt1, Ivanka E Ramírez de la Cruz1, Manuel A Reyes Rodríguez1
1Tecnológico Nacional de México - Instituto Tecnológico de Mérida, Av. Tecnológico km. 4.5, Mérida, Yucatán 97118, Mexico.
Abstract:
Quantifying total phenolic compounds (TPC) is essential in food and agricultural sciences. Although the Folin-Ciocalteu assay is versatile and widely reliable, non-phenolic reducing agents can interfere significantly in complex matrices. Diazonium salts, highly selective for aromatic electrophilic substitution, react exclusively with phenol derivatives and anilines. This study investigated 4-sulfophenyl diazonium chloride (4SPD) for TPC quantification. 4SPD was synthesized by diazotizing sulfanilic acid with sodium nitrite and hydrochloric acid, then characterized via 1H NMR, FT-IR spectroscopy and LC-MS. A calibration curve was constructed using gallic acid (40-400 mg L-1) with a quantification limit of 3 mg L-1. Operating signal was achieved at 50% methanol in water. The method demonstrated excellent precision, accuracy, and robustness with no significant deviation from 100% recovery. Validated across diverse simple and complex matrices with R2 = 0.933 correlation against HPLC-DAD, 4SPD proved to be a selective, precise, and robust method for TPC quantification.
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