Spectral Analysis Of Perfluorooctane Sulfonate In Environmental Water Samples

Perfluorooctane sulfonate?PFOS?and perfluorooctanoic acid?PFOA?are two representative perfluorinated compounds?PFCs?,which have been widely used in carpet,paper,textile and other fields of production because of their excellent chemical and thermal stability,hydrophobicity and oleophobic property.Due to their wide use,PFOS and PFOA have been detected in soil,atmosphere,water and other environmental media as well as animals and humans.PFOS and PFOA are resistant to degradation in the environment,and have environmental persistence,long distance migration,bioaccumulation and potential toxicity,posing hazards to the environment,animals and humans.Hence,it is very important to detect PFOS and PFOA in the environment.In this work,novel assays have been designed based on the resonance light scattering?RLS?and fluorescence analysis technology for the detection of PFOS and PFOA.The reaction mechanism was discussed,the experimental conditions were optimized,the interference was eliminated,and the proposed methods were used for the quantitative determination of PFOS and PFOA in the environmental water samples.The main contents include the following three aspects:?1?A RLS analysis method based on Janus Green B?JGB?for detecting PFOS was reported,which has the advantages of simplicity,rapid response time,low cost,high sensitivity and good selectivity.It was found that PFOS can form complexes with the protonated JGB through electrostatic interaction in pH 5.8 citric acid-sodium citrate?CA-NaCA?buffer medium resulting in remarkable enhancement of the RLS intensity of the system.The study shows that maximum scattering wavelength is located at 319.0nm and the enhanced RLS intensities(?I_RLS)are in proportion to the concentration of PFOS in the range of 0.05-9.0?mol/L?R²=0.9958?,with a detection limit of 5.6 nmol/L.Under the same experimental conditions,the interactions of various perfluorinated compounds?PFPrA,PFBA,PFPeA,PFHeA,PFHpA,PFOA,PFNA,PFBS?and JGB were studied and the scattering signal changes very little.Based on the above,a simple,highly sensitive and selective RLS analysis method was established for the detection of PFOS.The optimum reaction conditions were investigated.The reaction mechanism between JGB and PFOS was also studied by the absorption spectrum,scanning electron microscope?SEM?and combination ratio.This method has been successfully applied to the selective detection of PFOS in environmental water samples with RSD?2.7%.?2?A novel sensing method has been proposed for the highly sensitive detection of PFOS and PFOA in aqueous solution relying on the“turn-on”switch of erythrosine B?EB?-hexadecyltrimethylammonium bromide?CTAB?system.In pH 8.55Britton-Robinson?BR?buffer,EB can react with CTAB by electrostatic attraction,resulting in a strong fluorescence quenching of EB.With a subsequent addition of the CTAB,a red-shift occurred?11 nm?,followed by a significant increase in fluorescence at high surfactant concentrations.It was found that PFOS and PFOA can obviously enhance fluorescence intensity of EB-CTAB system.The enhanced fluorescence intensity?F-F₀?is proportional to the concentration of PFOS and PFOA in the range of0.05-10.0?mol/L with detection limit of 12.8 nmol/L and 11.8 nmol/L,respectively.The correlation coefficients are 0.9975 and 0.9953,respectively.The presented assay has been successfully applied to sensing PFOS and PFOA in real water samples with RSD?4.3%and 2.9%,respectively.?3?A novel sensing method has been proposed for the highly selective fluorescent visual detection of PFOS in aqueous solution based on carbon dots?CDs?and berberine chloride hydrate?BH?.It was found that the fluorescence of CDs(?_em=448 nm)decreased apparently in the presence of BH in pH 6.09 BR buffer solution.When PFOS was added to the system,the fluorescence was restored slightly at 448 nm and enhanced apparently at 533 nm,but no phenomenon occurred with other perfluorinated compounds.As a consequence,an obviously distinguishable fluorescence color variation?from blue to light yellow?of solution was observed.Under the optimized experimental conditions,the enhanced fluorescence intensities??I_F?at 533 nm are in proportion to the concentration of PFOS in the range of 0.22-50.0?mol/L?R²=0.9919?,with a detection limit of 21.7 nmol/L.The proposed approach has been successfully applied to the detection of PFOS in environmental water samples with RSD?1.1%.