Study On Optical Detection Of Nitrite Based On Griess And Inner Filter Effect

With the widespread application of nitrite in the fields of industry,agriculture,food and medicine,the pollution problems of nitrite residue have become increasingly serious.Long-term intake nitrite poses huge threats to public healthy and food safety,which might cause teratogenic,carcinogenic,mutagenic and other complications.Therefore,it is crucial to establish and develop simple,accurate,highly sensitive and selective methods for the detection of nitrite.Up to date,a lagre number of techniques for nitrite detection are mainly relied on traditional large-scale instrumentation equipments.These conventional analytical technologies offer highly sensitive and accurate assays of nitrite,but also suffer from many inherent defects such as expensive instruments,time-consuming procedures,complicated sample pretreatment,and requirement of skilled personnel,which hinder their widely application.Colorimetric and fluorescent optical technologies stand out simple operations,low-cost,rapid response and sensitivity in the field of trace sensing.In this work,three types of colorimetric/fluorescent sensing systems based on Griess assay were successfully developed for the determination of nitrite.All of the synthesized materials were characterized using Fourier Transform infrared spectroscopy(FT-IR),transmission electron microscope(TEM),Atomic Force Microscope(AFM),X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD).The specific research work of this dissertation is as follows:(1)A simple colorimetric sensing system based on the Griess reaction between phenosafranin(PS)and nitrite was developed.PS served as both of acting sites and signal producer.Under the optimal detection conditions,a good linear relationship(R~2=0.9977)was obtained in the concentration range of 0.1 to 20?M,with a theoretical detection limit of nitrite was 0.099?M(S/N=3).The color changes caused by nitrite can be easily observed by naked eyes at the nitrite concentration of 2?M.The developed sensor also shows good selectivity and reproducibility(RSD<5%).In addition,as-presented sensor displayed favorable recoveries(94.63%-109.94%)in the spiked ham,bacon,and sprouts samples.It indicates that the colorimetric sensor exhibits great potential application value in the actual sample nitrite detection.(2)We presented a mixture of 3-aminophenol(3-Aph)and organically synthesized green fluorescent coumarin derivative(CD)fluorescent sensing system(3-Aph/CD)based on the inner filter effect(IFE)for the nitrite detection.A good linear relationship(R~2=0.9961)between the fluorescent response(?F)and nitrite concentrations was acquired with a theoretical detection limit of nitrite was 0.054?M(S/N=3).Furthermore,3-Aph/CD fluorescent sensing system displayed excellent anti-interference ability and reproducibility(RSD<5%)in real-time nitrite detection.Most importantly,satisfactory recoveries(91.33%-109.44%)and reproducibility(RSD<5%)were achieved in spiked ham,bacon,and sprouts samples.These features indicate that the fabricated 3-Aph/CD fluorescent sensing system provides a good approach for the simple and rapid detection of nitrite in real samples.(3)We developed a sensitive and selective colorimetric and fluorescent dual-readout sensing system based on Griess assay and the inner filter effect(IFE)for nitrite detection under acidic condition.The sensing system was constituted with pH-independent carbon quantum dots(CQDs)and 3-aminophenol(3-Aph)with acidic conditions regulated using HCl.During the sensing procedure,reaction of 3-Aph and nitrite under acidic condition can yield a yellow-colored azoic compound(AZO),which gives the colorimetric readout.Meanwhile,the fluorescence CQDs(fluorescence reporter)quenches due to strong absorption of AZO,leading to fluorescence readout.Under the optimized conditions,the sensing system exhibit broad linear relationships towards nitrite in the range of 10 to 100 nM and 2.5 to 100?M,with theoretical detection limits of 8.76 nM and 1.5?M for the fluorescent and colorimetric readout,respectively.And the sensing system displays excellent capability of selectivity according to interferences study.Furthermore,the real samples testing of sprouts,bacon and ham sausage real samples demonstrated good recoveries and reproducibility of the sensing system.All these results suggested the proposed colorimetric and fluorescent dual-readout sensor can be a promising candidate for the nitrite detection in the real applications.