Preparation Of Novel Sorbents For Solid-phase Extraction And Their Application In Separation And Preconcentration Of Trace Components

The accurate determination of trace element in geological, biological and environmental samples is an important and challenging task in analytical chemistry;especially heavy metals are often routinely monitored in environmental water. Direct determination of trace elements at low concentrations by modern atomic spectrometric techniques is often difficult, not only because of the insufficient sensitivity of the methods, but because of matrix effects. For this reason, the preliminary separation and preconcentration of trace elements from matrix is often required.There can be no doubt that solid-phase extraction (SPE) is today the most popular sample preparation method. It is a very active area in the field of separation science (such as environmental, pharmaceutical, clinical, food and industrial chemistry, etc.). SPE has several major advantages in separation and preconcentration of trace elements, including (i) simple to operate;(ii) high preconcentration factor;(iii) rapid phase separation;(iv) and the ability to combine with different detection techniques. The methodology continues to evolve, through changes in format more than principle, in response to the desire to simplify the sampling process or facilitate automation. Advances are expected in sorbent chemistry, particularly class-specific sorbents for the isolation and clean-up of target analytes in complex matrices. Over time, various sampling formats and sorbents have been developed to facilitate the convenient processing of different sample types and to extend the scope of the method. At present, SPE is still an active area of research to develop new and more selective sorbents or procedures.Based on the research works of reference literature reported, some creative research works were carried out in this dissertation as follows:(1) A novel poly (acryl-benzoylamidrazone-acryl-benzoylhydrazine) chelating fiber was synthesized;the chelating fiber was used for preconcentrating and separating some noble metal ions incoluding Au(III) and Pd(IV), and some heavy metal ionsincluding Cr(III), Bi(III), Sn(IV), V(V), Ti(IV), and Zr(IV) from solution samples;and determination by inductively coupled plasma atomic emission spectrometry.(2) A new method was used for surface modification of T1O2 nanoparticles by dithizone or thiourea. The dithizone-modified TiO2 nanoparticles as solid-phase extractant for the simultaneous preconcentration of trace amounts of chromium and lead, and the thiourea-modified TiO2 nanoparticles for mercury before their determination by inductively coupled plasma atomic emission spectrometry.(3) A new molecularly imprinted polymer highly selective for enoxacin was prepared using molecularly imprinted technology;and the selective binding characteristics of the template polymer was evaluated by Scatchard analysis.The main research contents in present dissertation are listed as follows: 1. A novel poly(acryl-benzoylamidrazone-acryl-benzoylhydrazine) chelating fiber was synthesized simply and rapidly from polyacrylonitrile fiber and benzoyl hydrazine. The structure of the chelating fiber was verified with the help of FT-IR spectrum. The chelating fiber was used for preconcentrating and separating traces elements from sample solution: (1) The adsorption of heavy metal ions including Cr(III), Bi(III), Sn(IV), V(V), Ti(IV), and Zr(IV) was investigated. These heavy metal ions could be quantitatively enriched with the chelating fiber column at pH 4.0 and a flow rate of 1.0-10.0 mL min"1 and desorbed with 15 mL of 4.0 mol L"1 HC1 solution from the fiber column with the recoveries over 95%. Twenty to thousands-fold excesses of Ca(II), Mg(II), Cu(II), Ba(II), Zn(II), Mn(II), Al(III), and Fe(III) cause little interference with the concentration of the target metal ions and successful application of the chelating fiber in an analytical determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). (2) The parameters influencing the efficiency of the fiber for concentrating trace amounts of Au(III) and Pd(FV) were investigated in detail. Trace Au(III) and Pd(IV) were quantitatively enriched at pH 3 and desorbed with 5mL1.0 mol L"1 HC1 solution (with static method) or 1.5mL1.0 mol L"1 HC1 solution (with dynamic method). The saturation adsorption capacity of the fiber was found to be 0.25mmol g"1 for Au(III) and 0.69 mmol g"1 for Pd(rV).Enrichment and separation of trace Au(III) and Pd(IV) ions from solutionsamples by the chelating fiber can be carried rapidly and with high efficiency and accuracy.2. Nanometer TiC^ was modified using a new method, the dithizone-modified nanometer I1O2 (nanometer HO2-DZ) and the thiourea-modified nanometer T1O2 (nanometer I1O2-TU) as solid-phase extractant has been developed for the simultaneously on line separation and preconcentration of trace heavy metal ions from sample solutions. The adsorption behavior of Cr(III) and Pb(II) on the dithizone-modified nanometer TiCb and Hg(II) on the thiourea-modified nanometer T1O2 at low concentration was studied using inductively coupled plasma atomic emission spectrometry (ICP-AES). The optimum conditions for adsorption were studied in detail, and under the condition that the analytes could be adsorbed and recovered quantitatively. The adsorption capacity of the nanometer TiO2-DZ was found to be 5.8 mg g"1 and 22.5 mg g"1 for Cr(III) and Pb(II), respectively;and the adsorption capacity of the nanometer TiC^-TU was found to be 16.5 mg g"1 for Hg(II). The proposed methods were applied for the determination of trace analytes in foodstuff, plant and water samples with satisfactory results.3. A molecularly imprinted polymer was prepared using enoxacin as the template molecule, methacylic acid as a monomer and Pentaerythritol triacylate as a cross-linker. The imprinted polymer obtained was investigated in equilibrium binding experiments to evaluate the molecular recognition and binding characteristics of the enoxacin molecularly imprinted polymer using sensitized fluorescence of terbium. Scatchard analysis showed that two sites were produced in the polymer matrix and their dissociation constants were calculated to be 4.00xlO"5 mol/L and 1.13x10"3 mol/L, respectively. The substrate selectivity of imprinted polymer and non-imprinted polymer was investigated. The results showed that the imprinted polymer exhibited much higher affinity for enoxacin among the tested compounds.