Multi-signal Analysis Of Perfluorooctane Sulfonate In Environmental Water Samples Based On Scattering,Fluorescence And UV Absorption Spectroscopy

Perfluorinated Alkylated Substances?PFAAs?,is widely used in the past fifty years in the field of industrial and commercial?such as mine and oil well surfactants,electronic chemicals,floor polishes,carpet stain removal and bait station insecticides?.These contaminants are very persistent and refractory to different biological and chemical treatments and their presence in environmental matrix can give rise to toxic and bio accumulative effects,recognized as highly dangerous for eco-systems,biodiversity and human health.As a kind of typical PFAAs,Perfluorooctane sulfonate?PFOS?is the most extensively investigated PFAAs,despite the above features,PFOS are higher water-soluble than the other PFAAs,causing PFOS in the spread of the global scope of the internal environment.And it is now largely demonstrated that PFOS have immune-toxic effects of cell system and animals,especially for mammals.Therefore,it is urgent to develop a simple,efficient and low-cost PFOS determination method.In this paper,a triple-signal assay including fluorescence,UV absorption and resonance light scattering?RLS?was established to detect PFOS based on molecular spectroscopy.The mechanism of the system was discussed and the method was applied to the quantitative determination of PFOS in environmental water samples.The main contents are as follows:?1?A sensitive three-signal assay of perfluorooctanesulfonic acid?PFOS?was proposed.In pH 3.3 Britton-Robinson?BR?buffer solution,perfluorooctane sulfonate anions can react with the Nile blue A?NBA?by electrostatic attraction and hydrophobic force to form 1:1 ion-association complexes resulting in the intensity changes of fluorescence,UV absorption and RLS.And there is a certain relationship between the three signal changes with the concentration of PFOS,respectively.The change of absorption of NBA is proportional to the logarithm of the concentration of PFOS in the range of 0.1-4.0?mol/L?R²=0.9970?with a limit of detection?LOD?of 14.8 nmol/L,and RLS intensity changes is proportional to the concentration of PFOS in the range of2.0-12.0?mol/L?R²=0.9992?with a LOD of 119.5 nmol/L.And the change of fluorescence is proportional to the logarithm of the concentration of PFOS in the range of 0.05-4.0?mol/L?R²=0.9998?with a LOD of 3.2 nmol/L.The proposed assay exhibits good selectivity and sensitivity in the fluorescence signal.The scanning electron microscope?SEM?and Zeta potential were investigated for the mechanism study.This simple,sensitive and cost-effective fluorescence method has been applied successfully for the determination of PFOS in real water samples with RSD?2.1%.The recovery rate is 94.20-103.4%.?2?A simple,fast and cost-effective triple-channel optical assay for the determination of PFOS has been developed.The carbon quantum dots?CDs?were prepared by one-pot hydrothermal method and employed as probe for sensing PFOS.CDs react with PFOS to form ground-state complex,which brings about the intensity changes of three signals including fluorescence,UV absorption and RLS.And the changes of the fluorescence and absorption signals can be used for the visual detection of PFOS.And there is a certain relationship between the three-signal changes with the concentration of PFOS,respectively.The change of A/A₀ of CDs is proportional to the concentration of PFOS in the range of 0.5-8.0?mol/L?R²=0.9998?with a limit of detection?LOD?of 75.9 nmol/L,and I/I₀ changes is proportional to the concentration of PFOS in the range of 0.5-12.0?mol/L?R²=0.9992?with a LOD of 120.5 nmol/L.And the change of F/F₀ is proportional to the logarithm of the concentration of PFOS in the range of 0.2-12.0?mol/L?R²=0.9999?with a LOD of 18.3 nmol/L.The proposed assay exhibits good selectivity and sensitivity in the fluorescence signal.Fluorescence lifetime,transmission electron microscopy?TEM?images,Fourier transform infrared?FTIR?and Zeta potential were investigated for the mechanism study.Furthermore,this promising approach was also successfully applied to PFOS sensing in real water samples with RSD?2.1%.The recovery rate is 97.90-104.8%.?3?A novel strategy for PFOS detection was established by using an ratiometric nanosensor with the combination of fluorescence and second-order scattering?SOS?.The practical ratiometric nanosensor was synthesized by simply mixing fluorescent dye ethidium bromide?EB?and nitrogen doped carbon dots?NCDs?synthesized by a one-step hydrothermal method with Victoria Blue B,possessing three emission peaks at472 nm,560 nm and 600 nm under a single wavelength excitation of 280 nm,respectively.The EB served as the reference signal label,and the NCDs,having response to the analytes,acted as the response signal label.To achieve ratiometric detection,the fluorescence emission of the NCDs was turned off and the SOS emission was turned on with the addition of the target PFOS.To achieve colormetric detection,with the help of EB,the fluorescence of the system changed from green to orange.Under the optimal conditions,the difference of F₄₇₂/I₅₆₈ of the nanosensor had good linearity against the concentrations of PFOS within a linear range of 0-2.0?mol/L.The corresponding regression coefficient was 0.9993 and the limit of detection was as low as27.8 nmol/L,which was low enough for the detection of PFOS in water samples.Fluorescence lifetime,transmission electron microscopy?TEM?images,Fourier transform infrared?FTIR?and Zeta potential were investigated for the mechanism study.The proposed method was successfully applied to the detection of PFOS with RSD less than 1.67%.The results show that the as-prepared NCDs/EB ratiometric nanosensor has potential application of detection of PFOS in environmental monitoring.The recovery rate is 90.15-101.4%.