Applications Of Cloud Point Extraction And Nanomaterials In Capillary Electrophoresis

In modern society, humans may be exposed to a wide variety of environmental chemicals, including those with environmental endocrine-disruptive (EDC). However, the trace determination of EDC in the environment is difficult due to various factors, particularly their low concentrations and matrix effects. Therefore, a simple, fast, low-cost, sensitive and selective pre-concentration and separation techniques are usually required. The cloud point extraction (CPE) method was initially described by Watanabe, it is a new environment-friendly liquid-liquid extraction technology. It based on the cloud point phenomenon of surfactants, through changing experimental parameters (such as pH value, temperature, etc.) trigger separation. Because the cloud-point phenomenon occurs in two aqueous solutions by surfactants, CPE offers many advantages, such as low cost, environmental friendly and safety, high recovery and good extraction efficiency.In recent years, CPE as a methodology of separation and preconcentration are gaining many practical applications. The CPE technique has been widely used for the extraction of trace metals and organic compounds coupled with graphite furnace atomic absorption spectrophotometry (GFAAS), flame atomic absorption spectrophotometry (FAAS), high performance liquid chromatography (HPLC). Capillary electrophoresis (CE) has rapidly developed due to its short analysis time and clean analysis process and high resolution and efficiency, but the use of surfactant-based procedures as a sample preconcentration step prior to capillary electrophoresis (CE) analysis has not yet been fully explored. One problem associated with introducing a surfactant-rich phase into a bare fused-silica capillary was that the surfactant would be adsorbed onto the wall of the capillary, which resulted in a marked loss of efficiency and reproducibility. In this paper, new methods for the determination of trace EDC in environmental water was proposed and also discussed how to resolve the problem mentioned above.Nanoparticles are widely used in separation science, due to their high surface area as well as good biocompatibility. In CE technique, nanoparticles were added into the running buffer, which can be kinetically absorbed onto the inner surface of capillary to change or reverse EOF. Nanoparticles coupled to CE have remarkable potential in improving the separation efficiency and selectivity.Based on the previous reports, three innovative works were carried out in this paper.(1)As the first attempt, cloud point extraction (CPE) was developed for preconcentration of bisphenol A (BPA),α-naphthol andβ-naphthol before capillary zone electrophoresis (CZE) analysis. The parameters influencing the CPE efficiency, such as concentrations of Triton X-114, pH value, extraction time and temperature were evaluated systematically. After diluted with acetonitrile, the surfactant-rich phase of CPE can be injected directly into the CE instrument. The CZE baseline separation was achieved with running buffer (pH 9.5) composed of 50 mM sodium tetraborate in 30%(v/v) methanol, and an applied voltage of 25 kV. Under the optimized CPE and CZE conditions, an enhancement factor of 50 times could be obtained and the detection limits of the three analytes were found to be 1.67μ.g/L,0.8μg/Land 0.67μg/L for BPA, a-naphthol and P-naphthol, respectively. The proposed methods were shown to be a. green, rapid and effective approach for determination of three analytes present in river water samples.(2)pH-mediated dual-cloud point extraction (dCPE) coupled with capillary electrophoresis (CE) was applied to the determination of bisphenols and naphthols for the first time. In pH-mediated dCPE, the surfactant-rich phase significantly decreased during the second procedure, and the analytes were extracted into aqueous phase by simple pH-mediated and injected directly into the CE instrument. The baseline CE separation was achieved with running buffer composed of 30 mM sodium tetraborate and 8 mM SDS (pH 9.35). The factors affecting pH-mediated dCPE process were investigated and optimized. Under the optimum conditions,0.06 %(w/v) Triton X-114 was used as surfactant and 0.1 M NaOH solution was used as back-extract solvent to transfer the analytes into aqueous phase. This optimum pH-mediated dCPE extraction process was able to achieve an enhancement factor about 33-fold. The combination of pH-mediated dCPE extraction and CE method was validated with respect to precision, repeatability and accuracy. All the calibration curves between the peak areas and concentrations of the analytes showed good linearity (R20.9971-0.9994). The limits of detection were in the range from 0.68 to 3.5μg/L. The proposed method was shown to be a green, rapid and effective approach for determination of bisphenols and naphthols in spiked lake water and tap water samples.(3)Separation of lysozyme, bovine serum albumin and bovine hemoglobin using capillary electrophoresis (CE) with SiO2 nanoparticles as additives is reported. The factors that affect separation such as buffer concentration, additives (SiO2 nanoparticles, Polymer PVP, ACN), separation voltage and temperature were investigated. The baseline separation was achieved with running buffer composed of 50mMNaH2PO4-10mMH3PO4,15%ACN,10%PVP,0.35%SiO2, and an applied voltage of 30kV, temperature of 25℃, detection wavelength of 214nm. The results suggest that SiO2-04 nanoparticles could be used as effective additives for the separation of protein.