Self-ratiometric fluorescence approach based on room-temperature instantaneously synthesized carbon dots from Folin’s reagent and ethanol amine for determination of nitroxinil in water, milk, and food samples

Abstract

BackgroundNitroxinil has been used extensively to treat parasitic worms, mainly Fasciola, in food-producing cattle and sheep. The reported methods for nitroxinil analysis included expensive instrumentation, the need for skilled operators, and tedious procedures. Fluorimetry is one of the fastest and simplest methods widely used; hence, we aimed to develop a simple, cost-effective, and convenient fluorometric approach for the estimation of nitroxinil in various matrices. Compared with other detection methods, self-ratiometric fluorescent probes are considered a promising approach for the detection of analytes as their detection accuracy overcomes traditional fluorescence of the sensing probe in that it is not affected by the probe concentration, solution polarity, instrument parameters, and other factors. In this research, room temperature instantaneously synthesized carbon dots were used as a sensitive and selective self-ratiometric probe for the determination of the veterinary medicine nitroxinil in various matrices. ResultsA room-temperature synthesized quinone-ethanolamine carbon dots (RTQECDs) was fabricated using the instantaneous reaction of sodium 1,2-naphthoquinone-4-sulfonate (Folin’s) with ethanolamine, without any energy/catalyzing reagents, for the first time. The prepared carbon dots show green-blue fluorescence at 450 nm upon exposure to UV light at 365 nm with a quantum yield of 26.6%. Upon interaction with nitroxinil, the fluorescence intensity of RTQECDs at 450 nm is quenched and shifted to a longer wavelength at 475 nm. Meanwhile, the fluorescence of RTQECDs at 400 nm (absorbance maxima of nitroxinil) was more extremely quenched under the same conditions. Taking this in hand, a new RTQECDs self-ratiometric probe was developed for the determination of nitroxinil using the decrease in peaks at 450 nm and 400 nm and the shift of the fluorescence maxima to 475 nm as built-in reference peaks. The probe showed a quantitative increase in signal output of F475/F400 in the range of 0.10-30.0 μg/mL nitroxinil with a limit of detection of 30.0 μg/mL. The nitroxinil-sensing mechanism using RTQECDs is mainly ascribed to the partial secondary blue-type inner filter effect (IFE). The designed study was applied for the estimation of nitroxinil in veterinary dosage forms (recoveries; 99.78%−100.35%), river water (recoveries; 98.55%−101.53%), and (meat, liver, kidney, and milk (recoveries; 97.60%−104.25%). SignificanceThe novelty of our work includes the immediate synthesis of the sensing probe at room temperature, as well as its use as the self-ratiometric fluorescence probe for the determination of nitroxinil in veterinary samples, river water, and food products with excellent sensitivity down to 30 ppb. RTQECDs own the highest response and selectivity to nitroxinil compared with cations, anions, as well as other co-administrated drugs, including cefotaxime and ivermectin.