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Rare Earth Elements In Organic Complexes Derivative Absorption Spectra And Fluorescence Spectral Characteristics And Its Analytical Application

Posted on:2004-05-22Degree:DoctorType:Dissertation
Country:ChinaCandidate:W JiangFull Text:PDF
GTID:1111360152498173Subject:Analytical Chemistry
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The rare earth elements have special 4f electron structure, their chemical properties are very similar, consequently, it is difficult to find specific reactions for individual ions, especially in their mixtures. Rare earth complexes with organic ligands often show strong absorption and efficient fluorescence. In recent years, there is considerable interest in the study on these complexes for their potential application for determination of the rare earth elements, or conversely, for determination of the organic ligands, or as fluorescent probes in clinical chemistry and molecular biology, in material and environmental sciences. These have also long since become a major subject of our studies. My investigation works and results on the light absorption and fluorescence characteristics of rare earth elements organic complexes and their analytical applications have been summarized in this dissertation.In chapter one, first of all, the recent works for rare earth analysis by spectrophotometry were summarized. Subsequently, the luminescence mechanism of rare earth organic complexes and the effect factors on the fluorescence intensity was introduced briefly. The recent progresses in the study on the fluorescence of rare earth complexes and application for the determination of the rare earth elements and organic compounds, as fluorescent probes for bioactive materials analysis and as detection means in separation technology were reviewed in detail.In chapter two, the absorption spectra of the 4f electron transitions of the complexes of the neodymium, praseodymium, holmium and erbium with fieroxacin in the presence of CPC have been studies by normal and derivative spectrophotometry. Their molar absorptivity at the maximum absorption bands are about 5.3 (at 571 nm) times greater for neodymium, 2.8 (at 483 nm) times greater for praseodymium, 12.6 (at 448.5 nm) tines greater for holmium and 9.7 (at 519 nm) times greater for erbium than those in the absence of the complexing agents. Use of second-derivative spectrum can eliminate the interference fromother rare earths and to improve the sensitivity. Beer's law is obeyed in the range of 3.0-70 //g/ml for neodymium and holmium, 6.0-70 //g/ml for erbium, 12.0-70 //g/ml for praseodymium, respectively. The relative standard deviations are 1.9 % and 1.5 % for the 7.5 //g/ml of neodymium and holmium, and 2.1 % and 1.6 % for 15 //g/ml of praseodymium and erbium, respectively. Their detection limits ( signal-to-noise ratio = 3 ) are 3.2 //g/ml, 1.3 //g/ml, 1.1 //g/ml and 2.5 //g/ml for praseodymium, neodymium, holmium and erbium, respectively. A system for the simultaneous determination of the praseodymium, neodymium, holmium and erbium in rare earth mixtures with good accuracy and selectively is proposed.In chapter three, the absorption spectra of the praseodymium, neodymium, holmium and erbium complexes with enrofloxacin (ENFX) have been studied by normal and derivative spectrophotometry. The complex Pr-ENFX has maximum absorption at 350 nm at pH 6.0. The stoichiometry of the Pr-ENFX complex was calculated by the molar ratio and continuous variation methods. The ratio of Pr to ENFX was 1 ." 3. The absorption bands of the 4f electron transitions of the praseodymium complex with ENFX are enhanced markedly, especially the wavelength at 481 nm. Using the third-derivative spectrum, the calibration graph is linear over the range 2.5 X10'5 -3.5 X10"4 mol/L for praseodymium. The detection limit (signal-to-noise ratio of 3) is 1.4 X10"6 mol/L. The relative standard deviation is 1.2% for 7.0 X10"5 mol/L of praseodymium. A method for the direct determination of praseodymium in rare earth mixtures is described. Another method has been developed for the determination of neodymium, holmium and erbium in mixed rare earths. The method is based on the absorption spectra of 4f electron transitions of neodymium, holmium and erbium complexes with ENFX in the presence of TX-100. The second-derivative spectrum has been used to eliminate the interference and to improve the sensitivity. Beer's Law is obeyed for 3.0-60 //g/ml of neodymium and holmium, and 5.0-60 //g/ml of erbium. The relative standard deviations are 1.9%, 1.5% for 7.5 //g/ml of neodymium and holmium and 2.3% for 10.0 //g/ml erbium, respectively. The detection limits arecalculated to be 0.74, 0.85 and 1.2//g/mlfor neodymium, holmium and erbium, respectively. A method for the direct determination of neodymium, holmium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.In chapter four, the fluorescence characteristics of the europium and samarium-2-benzoyl-1,3-dione(BID)-cetyltrimethylammonium bromide (CTMAB), and europium-2-(2,2-diphenylacetyl)indan-1,3-dione (DPN)-DL-histidine -CTMAB systems were studied in detail. The effect factors of the systems and the methods for the determination of europium, samarium, DPN and BID are established. The excitation wavelengths for Eu and Sm-BID-CTMAB systems are 350 nm, and emission wavelengths are 612 nm for europium and 565, 606, 650 nm for samarium, respectively. The excitation and emission wavelengths for Eu-DPN-DL-histidine-CTMAB system are 330 and 612 nm. Europium and samarium could be determined by using Eu- and Sm-BID-CTMAB systems in the range of 1.0x10'9~1.0Xi0"5mol/L and 2.0X10'8~5.0X10~5mol/L, respectively. 1.OX1O'6~2.OX1O'5 mol/L of BID also can be determined. By using Eu-DPN-DL-histidine-CTMAB system, the fluorescence intensity was a linear function of the concentration of DPN in the range of 6.0 X 10"7~9.0X 10'5 mol/L. The detection limits for europium, samarium, BID and DPN are 1.0X10'10 mol/L, 1.0 X10"9 mol/L, 1.0 x 10"7 mol/L and 8.0 X10"8 mol/L, respectively. Standard addition method was used for the determination with satisfactory results.In chapter five, the new lanthanide-sensitized luminescence system europium-sparfloxacin (SPLX)-1,10-phenanthroline (phen)-sodium dodecyl sulfate (SDS) and the fluorescence enhancement complex systems of europium and SPLX by yttrium, lutetium and gadolinium in SDS micelle solution at room temperature were discovered. The fluorescence characteristics of the systems were studied in detail. The effect of the experimental conditions on the fluorescence intensity was defined. The study results show that the binary complex formed by europium with SPLX in SDS micelle solution can emit intrinsic fluorescence of europium ion. In the presence of yttrium, lutetium and...
Keywords/Search Tags:Rare earth element, Organic complex, Derivative absorption spectrum, Fluorescence spectrum.
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