Sensitive naked eye detection and quantification assay for nitrite by a fluorescence probe in various water resources

https://doi.org/10.1016/j.saa.2018.04.025Get rights and content

Highlights

  • PyI was synthesized by a very simple and facile one-pot method and the detection of NO2- is a simple one-step process.

  • PyI can be used for sensitive visual detection of nitrite ions under more mild condition with pH value from 2 to 5.

Abstract

An uncontrolled increase of nitrite concentration in groundwater, rivers and lakes is a growing threat to public health and environment. It is important to monitor the nitrite levels in water and clinical diagnosis. Herein, we developed a switch-off fluorescence probe (PyI) for the sensitive detection of nitrite ions in the aqueous media. This probe selectively recognizes nitrite ions through a distinct visual color change from colorless to pink with a detection limit of 0.1 μM. This method has been successfully applied to the determination of nitrites in tap water, lake water and Yellow River water with recoveries in the range of 94.8%–105.4%.

Introduction

Nitrite (NO2) is widely distributed in natural world and is one of the most widespread nitrogen compounds. Once reacts with proteins, nitrite ions are prone to form highly carcinogenic N-nitrosamines [1]. Excessive consumption of nitrites will lead to various diseases such as esophageal cancer and infant methemoglobinemia [[1], [2], [3]], etc. The maximum contaminant level (MCL) of nitrite, legislated by the U.S. Environmental Protection Agency (EPA), is 1 ppm (21.7 μM), and the analogous guideline value set by the World Health Organization (WHO) is 3 ppm [4,5]. Several methods have been reported for the detection of nitrite ions, including chromatography [[6], [7], [8]], electrochemical [[9], [10], [11], [12], [13], [14], [15], [16]] and spectroscopic methods [[17], [18], [19], [20], [21]]. Spectroscopic methods are the most widely used for nitrite determination due to the excellent limits of detection, facile method and can be used for visual on-site analysis. Griess Assay is undoubtedly the most common approach to detect nitrite which first developed in 1858 [22] and used till now. The assay typically relies on the diazotization of a suitable aromatic amine by acidified nitrite with the subsequent coupling reaction providing a highly coloured azo chromophore, from which the concentration of nitrite can be assessed [23]. Yang et al. designed a novel probe (NT555) for nitrite detection, which displays superior detection kinetics and sensitivity [24]. Ramaiah et al. developed a novel aza-BODIPY probe that selectively recognizes the nitrite ions through a distinct visual color change from bright blue to intense green with a sensitivity of 20 ppb [4]. Banerjee et al. reported a rhodamine based “turn-on” type fluorogenic probe which detects trace amount of nitrite ions in water as low as 4.6 ppb [25]. These probes have the analogous mechanism with Griess Assay. Almost all reported fluorescence probes for detection of nitrite ion have to satisfy the strong acid condition (pH = 0) [4,19,24] and some even required low temperature (0 °C) [25]. Recently, many nitrite sensors based nanoparticle probes have been reported [[26], [27], [28], [29], [30], [31], [32], [33]]. Most of them base on the nanoparticles modified with recognized groups to detect nitrite ions. Some of these methods have complicated procedure, expensive and may have extraordinary biotoxicity for human health [34].

The detection of NO2 by the Griess assay is a two-step process, including the initial addition of an aliquot of NO2 containing solution into an acidic solution of sulphanilamide to generate the electrophilic diazonium salt and subsequent addition of a naphthylethylenediamine solution to furnish an azo dye. It is a colorimetric assay with a detection limit of 2.5 μM and need strongly acidic media (pH = 0–1) [35]. Herein, we designed and synthesized a novel fluorescence probe (PyI) for the detection of nitrite ions by one-pot method and the detection of nitrite ions is a simple one-step process with a detection limit of 0.1 μM. Moreover, it can be used for sensitive visual detection of nitrite ions under the more mild condition with pH value from 2 to 5.

Section snippets

Materials

2,6-Pyridinedicarbonyl dichloride was purchased from J&K company (Beijing, China). 5-Aminoindole was obtained from Meryer company (Shanghai, China). 4-Dimethylaminopyridine (DMAP) was purchased from Aladdin company (Shanghai, China). 4-(2-hydroxyethyl)-1-piperazineethanesulfonicacid (HEPES) was purchased from Energy Chemical Technology (Shanghai, China) Co., Ltd. Anhydrous acetonitrile and triethylamine were pretreated with CaH2 and fractional distilled before use. Ultrapure water was produced

Characterization of the Probe PyI

PyI was easily synthesized via a facile one-step reaction with high yield (72%) shown in Fig. 1. The final product was unambiguously characterized on the basis of spectroscopic and analytical evidence (supplementary material, Figs. S1−S3).

X-ray Crystallography

Single-crystal X-ray diffraction analysis reveals that the PyI crystallizes in the monoclinic system space group P21/c (Table S1). The asymmetric unit contains one PyI and a methanol, as shown in Fig. 2. Hydrogen atom which located on acylamino nitrogen N(2)

Conclusion

In summary, we have developed a novel fluorescence probe PyI for the sensitive detection of nitrite ions in water by a direct and simple method. The Probe PyI can selectively detect nitrite ions by a distinct visual color change from colorless to pink with a detection limit of 0.1 μM. The probe PyI can be used for the detection of nitrite ions in the presence of other competing ions in natural water resources.

Acknowledgements

This work was financially supported by National Natural Science Foundation of China (No.21575055).

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