The widespread use of fertilizers and indiscriminate discharge of partially treated and untreated wastewater has increased the presence of ions as ammonium (NH4+), nitrate (NO3), and nitrite (NO2-) in the environment. The extended consumption and increased release of NO2- ion into the environment has led to human health hazards and disturbance in the nitrogen biogeochemical cycle. World health organization and Bureau of Indian standards has set the permissible limit of NO2- ion in drinking water as 1 mg L−1 (2.17 μM) and maximum contaminant level (MCL) in public water system as 10 mg L-1 (21.7 μM) Therefore, an efficient monitoring of NO2- ion in the water systems is an inexorable task. In this regard, several methods based on spectrometric, fluorescence, chromatographic, and electrochemical analysis has been employed for the detection of NO2- in food, water, and industrial effluents. Among those spectrophotometric methods are the most widely used methods which involve diazotization or nitrosation reaction. In this study, diazotization ability of the basic fuchsine (BF) was utilized as a colorimetric sensor for NO2- ion. Initially, the study was carried out in liquid phase to understand the practicality and selectivity of the proposed sensor for NO2- detection. The lower detection limit of the acidified BF solution against NO2- was found to be 0.005 mg/L. Later, a low-cost colorimetric strip based sensor was developed by dip-coating the BF on Whatmann filter paper. The surface properties of the developed strips were investigated using various analyses, i.e., Fourier transform infrared (FTIR), FT-Raman, UV-diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), and scanning electron microscopy (SEM)). From these results and leaching tests, the efficacy of the dip-coating methods was estimated. The selectivity of the probe in both liquid and strip was verified in the presence of other ions such as CH3COO-, Br-, NO3-, CO3-, SO42-, Fe3+, Ba2+, Cu2+, Mn2+, Ni2+, Co2+, Zn2+, Ca2+, Mg2+, and Na+ in single and multicomponent system. The naked eye sensitivity of the developed colorimetric sensor strip was 1 mg/L and spectrophotometrically it was 0.09 mg/L, respectively. Efficacy of the developed probe was tested for real water samples. The sensing mechanism was assessed based on the diazotization reaction which involves attack of nitrosoyl ion towards secondary amine group of the BF (pink) and forms N-Nitrosoamine (colorless).

Development of low-cost colorimetric sensor for the detection of aqueous nitrite ion

2019 Fall National Meeting

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