A simple indicator displacement assay ensemble for rapid and selective determination and naked-eye detection of Cu²⁺ and citrate through a novel diazo-based colorimetric chemosensor

ABSTRACT

Citrate as a naturally occurring ion with important biological roles, especially in metabolic cycles, and as an important biomarker in the early diagnosis of many diseases, including prostate cancer, has received special attention. In the present study, a novel, sensitive, fast and simple colorimetric bisazo-based chemosensor was developed for sequential determination and naked-eye detection of Cu²⁺ and citrate. UV-Vis spectroscopic studies showed that Reactive Red 141 (RR¹⁴¹) exhibits high selectivity and sensitivity towards Cu²⁺ in the presence of many other cations in deionised water (10 mmol L⁻¹ MES(2-(N-morpholino)ethanesulfonic acid)/NaOH buffer solution, pH 6.0) and complex real samples as well. The obvious colorimetric response while interaction with copper and citrate is due to complexation between RR¹⁴¹ and Cu²⁺, and then the citrate detection occurred through metal transfer from the RR¹⁴¹-Cu²⁺ towards the citrate anion releasing RR¹⁴¹ via an indicator displacement route. The mechanism of detection has been carefully investigated using the semi-empirical calculation method of MM² molecular mechanics. The proposed detection method for citrate ion has a detection limit of 0.15 µmol L⁻¹ and a satisfactory linear range of 1.92–45.96 µmol L⁻¹, which is consistent with the desired average diagnostic concentration in prostate cancer (less than 2 mmol L⁻¹). Our studies’ results indicate the high capability of the developed chemical sensor for quantitative and qualitative citrate detection in various complex media, including biological and clinical real samples.

KEYWORDS:

• Colorimetric chemosensor
• bisazo dye
• copper (II) ions
• citrate ions
• sequential determination
• MM² molecular mechanics

Acknowledgments

The authors desire to be renowned for the support of this work with the aid of the Department of Chemistry, Payame Noor University 19395-4697 Tehran, Islamic Republic of Iran. The authors also wish to acknowledge Dr Gohar Deilamy-Rad.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/03067319.2023.2289637.

Additional information

Funding

The work was supported by the Payame Noor University [IDs d/7/47416 and Layout code 3146].