In this study, a novel reagent was developed for sensitive detection of iron (II) sulfate, spectrophotometrically. A novel thio-anthraquinone derivative, 1-(Dodecylthio)anthracene-9,10-dione (3), was synthesized from the chemical reaction of 1-Chloroanthraquinone (1) and 1-Dodecanethiol (2) by an original reaction method and was used in the preparation of the novel reagent called Catal's reagent. A synthesized thio-anthraquinone analogue (3) waspurified by columnchromatography, and its chemical structurewas characterized by spectroscopic methods such as Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), and ultraviolet (UV)-visible spectrophotometry. The chemical and molecular structure of the developed thio-antraquinone derivative (3) was illuminated using computational methods with the GaussView5 and Gaussian09 programs. Various solvents including ethanol, methanol, and acetonitrile were examined in the preparation of the reagent. A concentration range from 0.2 mg mL(-1) up to 10 mg mL(-1) of iron (II) sulfate heptahydrate solution in distilled waterwas prepared. The absorption spectra of Catal's reagent (0.816mM) showed three peaks between 185 nm-700 nmofwavelength. However, after the reactionwith H2O2 and the 30 mM trisodium citrate dihydrate mixture in the presence of an iron sulfate (II) solution, a single peak was observed, producing a stable and reddish/brownish homogenous solution (lambda max= 304 nm). The following concentrations of iron (II) sulfate heptahydratewas examined using developed protocol and the reagent, and the concentrationswere measured spectrophotometrically at 304 nm, 0.2-1mg mL(-1). Absorbances of reaction mixtures of iron (II) sulfate remained stable up to 48 h. The results indicated that the novel Catal's reagent can be used for sensitive spectrophotometric detection of iron (II) sulfate in aqueous solutions. (c) 2020 Elsevier B.V. All rights reserved.