| It is well known that an exceeding amount of aluminium or copper in one's body is very dangerous, what's more, waste water with too high contents of this two kind of ions can not be treated with biological methods. As a result, there are an increasing importance in the research of the determination of them, within which, the most common methods are spectrophotometric techniques, atomic absorption spectrometry (AAS), oscillopolarography, high performance liquid chromatography (HPLC) and so on. But the methods listed above have their disadvantages: AAS needs expensive instruments; spectrophotography has poor sensitivity and its operations are very complex.Catalytic spectrophotometry, developed from common spectrophotography, having ideal sensitivity and not needing too expensive instruments, has become the most often used method in developing countries for the determination of trace metals. The research of catalytic spectrophotometry has become a hot point in the field of analytical chemistry.In the basis of retrieving science literatures and doing large amounts of experiments, the author of this dissertation found the ion of aluminium can facilitate the oxidation decolorization reaction of indigo carmine by ammonium persulfate and obtained a new method for the determination of trace aluminium: A novel catalytic spectrophotometric procedure for the determination of aluminium(III) with IC. Following experiments show the ion of copper can facilitate the same decolorization reaction in a larger extent and catalytic spectrophotometric procedure for the determination of trace copper(II) with IC has also been developed.The targets of the experiments in this dissertation include: finding the optimum reaction conditions such as the range of pH, the dosage of reactants, reaction time and temperature; plotting the calibration graph under the optimum conditions; testing the interference effects of ordinary ions; applying to determination of aluminium(III) or copper(II) in real samples by this proposed method; discussing the reaction mechanisms.The results of the experiments are : catalytic reaction for the determination of aluminium(III) with IC should carry out in 1ml hexamethylene tetramine-hydrochloric acid buffer solution(pH=5.4); the dosage of the oxidant—ammonium persulfate is 1ml, the dosage of the surfactant—TritonX-100 is 2ml, the dosage of the indicator—IC is 1ml; after reacting in 30℃ constant temperature water bath for about 28 min, theabsorbance of both catalyzed and uncatalyzed reaction mixtures should be tested in 608nm. The regression equation of the calibration graph is ΔA=5.2789×10-3C Al(III)ï¼2.3991×10-3 with a correlation coefficient of r=0.9992. Aluminium(III) concentration is linear for 0～3μg/25ml,and the detection limit is 0.49μg/25ml. Most of the foreign ions except for copper(II) and iron(III) do not interfere with the determination.The interference of copper(II) and iron(III) can be removed by extraction with sodium diethyldithiocarbamate(DDTC)-carbon tetrachloride. This procedure had been used to detect the concentration of aluminium(III) in flocculation, tea-leaf, wastewater and human hair . The recoveries were 98.6～101.97%. This system is a zero-order reaction for Al3+, and it is a first-order reaction for IC. The apparent rate constant is 2.62×10-5s-1 and the apparent activation energy is 6.60kJ/mol.Catalytic reaction for the determination of copper(II) with IC should carry out in 1ml sodium borate-hydrochloric acid buffer solution(pH=9.09); the dosage of the oxidant—ammonium persulfate is 4ml, the dosage of the surfactant—Tween-20 is 4ml, the dosage of the indicator—IC is 1ml; after reacting in 60℃ constant temperature water bath for about 15 min, the absorbance of both catalyzed and uncatalyzed reaction mixtures should be tested in 608nm. In the absence of surfactant, the regression equation of the calibration graph isΔA=0.1582CCu(II)(μg/25ml) ï¼9.455×10-3 with a correlation coefficient of r=0.9987. Copper(II) concentration is linear for 0～3μg/25ml.;... |
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