| Perfluorooctane sulfonate (PFOS) and perfluorooctane acid (PFOA) are anthropogenic organic pollutants, which are recognized as an emerging problem in water environment due to the persistence, bio-accumulation, long range transportation and toxic effects, and could potentially pose a risk to human health and the environment. Thus, detection of PFOS and PFOA are very important in environmental monitoring. This paper reports a series of light sensors for PFOS and PFOA detection based on the resonance light scattering technology and fluorescence spectroscopic technology. Simultaneously, molecular imprinting technique is applied in order to achieve high selectivity in the experiment. Reaction mechanism was discussed. Then, the methods applied to measure PFOS and PFOA in real water samples. Main contents are as follows:(1) This report presents a simple, rapid, and cost effective, ethyl violet (EV)-based resonance light scattering (RLS) assay for determination of PFOS. In pH2.87Britton-Robinson (BR) buffer solution. EV can be protonated and reacts with PFOS by electrostatic interactions to produce ion-association complexes. Simultaneously, the interaction lead to enhance resonance light scattering intensities greatly, which are characterized by peaks at326nm. It is found that the enhanced RLS intensity is proportional to the concentration of PFOS in a range of0.02μmol/L to10.0μmol/L. The limit of detection is2.0nmol/L. In addition, UV/Vis absorption spectrum and scanning electron microscope (SEM) image both are investigated to further validate the reaction mechanism. The interference of coexisting foreign substances and the optimum test of reaction conditions, including pH value, reaction time and ionic strength, are also investigated. This method has been successfully applied to the determination of PFOS in environmental water sample with RSD≤4.5%. The present approach displays the advantages of simplicity, rapidity and cost efficiency for the determination of PFOS.(2) A simple, fast method for the determination of PFOS was developed.4-(methylphenyl)-2,2’:6’,2"-terpyridine(mptpy), which has a distinct fluorescence emission after coordination with the Zn(II) ion, has been found to display a simple, time-saving, rapid recognition for PFOS based on the decrease of the fluorescence intensity of mptpy-Zn(II) for the first time in complex environmental samples. Under optimum conditions, the relative fluorescence intensity is decreased linearly with the increase in the concentration of PFOS in the range of0.4-17.0μmol/L with correlation coefficient of0.9961, and the detection limit was40nmol/L. The method has been applied to the determination of PFOS in environmental water samples with satisfactory results. The proposed method manifested several advantages such as rapid reaction, low cost and ease of operation.(3) A novel fluorescent sensor based on core-shell quantum dots (QDs) was synthesized for determination of perfluorooctane acid (PFOA) in water sample, where molecularly imprinted polymer (MIP) was incorporated in core-shell quantum dots-based sensing system to detect the PFOA for the first time. A simple method was used to fabricate CdTe@CdS QDs which QDs can be encapsulated with silica imprinted film through a one-pot sol-gel reaction. The final composite was developed by anchoring the MIP layer on the CdTe@CdS QDs using3-aminopropyltriethoxysilane (APTES) as functional monomer and tetraethoxysilane (TEOS) as cross linker by means of the hydrolysis and condensation reaction in the presence of aqueous ammonia solution as the catalysis. The combination of QDs and MIP showed stable fluorescent property and template selectivity. The fluorescence of the MIP-coated QDs composite can be efficiently quenched when PFOA molecules rebound to the binding sites. The composite was applied to the detection of the non-emissive PFOA and exhibited a good linearity in range of0.25～15.00μmol/L with the detection limit of25nmol/L. FTIR spectra of QDs@MIP and QDs@NIP have been contained, which further confirmed the successful imprinting of PFOA into the silica matrix. The morphology of QDs@MIP and QDs@NIP were studied by SEM, It was observed that the MIP showed similar appearances, and both of them exhibited as microspherical particles. In order to illustrate the selectivity, selective experiments about the analogues quenched fluorescence intensity of QDs@MIP were also made, which further supported that MIP shows an affinity for the template molecule over other structurally related compounds. Furthermore, the proposed method was successfully intended for the determination of trace PFOA in environmental water samples without the interference of other molecules and ions. |
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