Study Of New Technique For Separation And Preconcentration Of Trace Metal Ions With Microcrystalline Triphenylmethane

With the development of chemical industries and the wide use of pesticides, the content of pollutants in natural water, soil, atmosphere and biological samples is higher than that was lawfully allowed. With samples becoming more and more complicated, the analysis of trace level ofμg/mL,ng/mL, even pg/mL is needed. And with the number of analytes in these samples increases, the separation and determination of ultra-trace elements from complicated matrixes has become the important problem to be solved. The separation technique, therefore, must be so effective and selective as to meet the analytical requirements. On the other hand, with people's awareness of protecting environment, the content of pollutants in the environment has been strictly controlled, which make it necessary to develop some separation technique with rapidity, simplicity, sensitivity and precision. In analytica chemistry, the degree of sample pretreation has an important effect on the sensitivity, accuracy and the analytical speed. In order to increase the preconcentration efficiency, a new technique of separation and preconcentration---Solid-Phase Extraction (SPE) has been invented.In this paper, the development, principle, advantage, equipment and application of SPE in recent years are summarized, and a way of further development in SPE is pointed out by using traditional material modified by organic reagents as the stuffing, increasing the separation capacity, reproductivity and improving the automatic equipment. Moreover, the application of triphenylmethane as an adsorbent in trace analysis is summarized, developing a new separation and preconcentration method for the determination of trace heavy metal ions with microcrystalline triphenylmethane. The full text consists of five chapters. The first chapter concerns a new method for Mo(VI) separation and preconcentration with microcrystalline triphenylmethane loaded with salicyl fluorone prior to determination by spectrophotometry. It is the first time that triphenylmethane was used as an adsorbent to preconcentrate and separate trace amount of molybdenum in water samples. The effects of different parameters, such as acidity, stirring time and various metal ions, the amounts of triphenylmethane and salicyl fluorone etc. on the enrichment yield of molybdenum have been studied to optimize the experimental conditions. In the presence of salicyl fluorone (SAF), MoO22+ can react with SAF to form electrically neutral chelate complex MoO2SAF, and the resulting MoO2SAF can be adsorbed and enriched on the surface of microcrystalline triphenylmethane by the intermolecular action strength. This method has the advantages of high recovery, good selectivity, high enrichment factor, environment friendly, and so on.The second chapter concerns Zn(II) separation and preconcentration with microcrystalline triphenylmethane loaded with malachite green (MG). A new method for the separation and preconcentration of zinc using microcrystalline triphenylmethane loaded with malachite green was developed prior to the determination by FAAS. The complex anion Zn(SCN)42- and cation MG+ can form electrically neutral ion-association complex [Zn(SCN)42-]·(MG+)2, and the resulting ion-association complex can be adsorbed on the surface of microcrystalline TPM. The proposed method was successfully applied to the determination of trace zinc in tap water, river water and lake water.The third chapter reports the preconcentration and separation of trace amounts of vanadium(V). The present paper describes a novel method for vanadium(V) preconcentration using microcrystalline triphenylmethane loaded with crystal violet (CV) prior to the determination by spectrophotometry. By controlling pH 4.0, V(V) can react with CV loaded on microcrystalline TPM to form ion-association complex V(V)-CV, the resulting V(V)-CV can be adsorbed on the surface of microcrystalline triphenylmethane. While, Cd(II), Pb(II), Mn(II), Co(II), Cu(II), Fe(III), Ni(II), Al(III), Zn(II) and Hg(II) are not adsorbed at all. V(V) can be completely separated from Cd(II), Pb(II), Mn(II), Co(II), Cu(II), Fe(III), Ni(II), Al(III), Zn(II) and Hg(II). The proposed method has been successfully applied to the determination of trace vanadium in various water samples with satisfactory results.The fourth chapter concerns copper preconcentration and separation using triphenylmethane modified with malachite green (MG+) as an adsorbent. It is the fist time that triphenylmethane is used as an adsorbent to enrich trace copper in various water samples. The effects of different parameters, such as the amounts of NH4SCN, malachite green, ascorbic acid and triphenylmethane, acidity, stirring time and various metal ions etc on the enrichment yield of Cu(II) have been discussed to select the experimental conditions. In the presence of SCN-, Cu(II) can be reduced to Cu(I) by ascorbic acid in the solution; and then Cu(I) reacts with SCN- to form complex anion Cu(SCN)2-, and the resulting Cu(SCN)2- react with MG+ to form [Cu(SCN)2-]·(MG+) which can be retained on the surface of microcrystalline TPM. After desorption, the amount of Cu(II) in environmental water samples was determined by flame atomic absorption spectrometry (FAAS).The fifth chapter concerns copper preconcentration and separation using using phenolphthalein loaded with 1-(2-pyridylazo)-2-naphthol (PAN) as solid phase extractant. Under the optimum conditions, Cu(II) can be totally adsorbed on the surface of microcrystalline phenolphthalein. By controlling appropriate acidity (pH=1.0), Cu(II) is completely separated from Cd(II), Pb(II), Mn(II), Co(II), Fe(III), Ni(II), Al(III), Zn(II) and Hg(II) in the solution. 1-(2-pyridylazo)-2-naphthol retained on microcrystalline phenolphthalein reacts with Cu(II) to form chelate Cu(II)-PAN, and the resulting Cu(II)-PAN can be quantitatively retained on the surface of microcrystalline phenolphthalein. After desorption, the amount of Cu(II) can be determined by spectrophotometry. The proposed method has been successfully applied to the determination of trace copper in encironmental water samples with satisfactory results.