共查询到19条相似文献,搜索用时 85 毫秒
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示波电位滴定法测定COD的研究 总被引:9,自引:0,他引:9
本文用回流处理样品,以示波电位滴定法测定水中化学耗氧量(COD),方法简单,终点变化敏锐,特别适宜于有色和有悬浊物的样品分析。 相似文献
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《中国化学会会志》2018,65(2):217-224
A new and simple potentiometric method is developed to determine the stability constants of cysteine complexes with Mn(II), Cu(II), Zn(II), Cd(II), and Ce(III) metal ions using a modified Bjerrum method. Potentiometric titrations were performed in water and water/dioxane mixtures at five different temperatures. The least and highest stable complexes were those of Cu(II) and Zn(II), respectively. Furthermore, by conducting the experiments at temperatures of 15, 20, 25, 35, and 45 °C, the thermodynamic parameters ΔH°, ΔS°, and ΔG° for the pertinent complexes were calculated. The results show that the ΔH° values of the complexes are positive except for Zn(II). Negative values of ΔG° are evidence for the spontaneity of the reactions. 相似文献
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The construction and performance characteristics of pentoxifylline selective electrodes were developed. Two types of electrodes: plastic membrane I and coated wire II were constructed based on the incorporation of pentoxifylline with phosphotungstic acid (PTA). The influence of membrane composition, kind of plasticizer, pH of the test solution, soaking time, and foreign ions on the electrodes was investigated. The electrodes showed a Nernstain response with a mean calibration graph slope of 56.77 ± 0.19 and 55.76 ± 0.71 mV decade‐1 at 25 °C for electrode I and II respectively, over pentoxifylline concentration range from 1.0 × 10‐5‐1.0 × 10‐2 and 9.0 × 10‐6‐1.0 × 10‐2 mol L‐1, with detection limits 4.89 × 10‐6 and 3.90 × 10‐6 mol L‐1 for electrode I and II, respectively. The pH range of the constructed electrodes was 4‐6. Interferences from common cations, alkaloids, sugars, amino acids and drug excipients were reported. The results obtained by the proposed electrodes were also applied successfully to the determination of the drug in its pharmaceutical preparations and biological fluids. 相似文献
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A potentiometric titration for cobalt(II) determination in the presence of Co(III) based on the oxidation of Co(II) with Na2CrO4 in ethylenediamine medium and back-titration of the oxidant excess with (NH4)2Fe(SO4)2 in acid medium is described. The titration is monitored with a Pt indicator electrode and carried out until the greatest jump of potential from one drop of titrant appears. A RSD smaller than 1.5% has been obtained for 50–300 μmol Co(II). The method proposed was applied in the analysis of a new type electroless copper plating solutions containing Co(II)-ethylenediamine complex compounds as reducing agents. Cu(II), Co(III) and Cr(III) do not interfere in the determination of Co(II). 相似文献
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This study reports on two types of glutamate sensors based on chitosan, i) heterogeneous membrane and ii) coated wire (CWE). The linearity ranges are: i) membrane, 1.0×10?5 to 1.0×10?1 M and ii) CWE, 1.0×10?5 to 1.0×10?3 M. The LODs, and pH ranges are i) membrane, 5.0×10?6 M and 4–8 and ii) CWE, 1.0×10?5 M and 3–5, respectively. The presence of ionic species normally found in foodstuffs did not interfere in both electrodes. Interference in CWE was minimized by prior dilution of the sample. The CWE was further investigated for on‐line analysis. The material for proposed electrodes was cheaper and environmental friendly. Hence, they were suggested as alternative tools for the analysis of glutamate. 相似文献
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乙醇-水介质中氟-铝沉淀电位滴定体系研究 总被引:2,自引:0,他引:2
由于氟-铝的多级络合反应,在水溶液中用氟化物直接滴定铝没有明显的电位突跃,若用乙醇-水介质,则电位突跃明显[1~3].本文对乙醇-水介质中氟-铝沉淀电位滴定体系的化学平衡进行了研究.测定了在不同浓度的乙醇介质中氟-铝的络合比及各级络合物的稳定常数等参数.实验表明用F-电位滴定测定铝可取得较好结果. 相似文献
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Simultaneous determination of cysteine (RSH) and cystine (RSSR), two important sulfur-containing amino acids, in capillary electrophoresis (CE) has been an analytical task. Dual-microelectrode amperometric detection seems to be a good scheme, but significant difficulty in electrode construction and poor detection limit for RSSR determination remain major short-comings. In reverse pulse amperometric (RPA) detection, the applied potentials are repeatedly pulsed back and forth between the reducing initial potential (e.g., Ei = ?1.4 V) and the oxidizing final potential (e.g., Ef = 0.0 V) at a single, gold-mercury amalgam (Au/Hg) microelectrode. At Ei, RSSR is reduced to RSH which causes catalytical oxidation of the Au/Hg amalgam microelectrode when the potential is pulsed to Ef. The resulting anodic current is then recorded. Therefore, by using RPA detection after CE separation, RSH and RSSR can be simultaneously determined. 相似文献
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The performance characteristic of sensitive screen-printed (SPE) and carbon paste (CPE) electrodes was investigated for the determination of diphenhydramine hydrochloride (DPH) drug in pure, pharmaceutical preparations and biological fluids. Different experimental conditions namely types of materials used to prepare the working electrode (plasticizer), titrant, pH, temperature and life time were studied. Under these conditions, the SPE shows the best performance than CPE with respect to total potential change and potential break at the end point. The SPE and CPE exhibit suitable response to DPH in a concentration range of 1.0.10− 2 to 1.0.10− 6 mol/L with a limit of detection 9.70.10− 7 and 9.80.10− 7 mol/L, respectively. The slope of the system was 55.2 ± 1.0 and 54.7 ± 1.0 mV/decade over pH range 3.0–8.0 and 3–7 for SPE and CPE, respectively. Selectivity coefficients for DPH relative to a numbers of potential interfering substances were investigated. The SPE and CPE show a fast response time of 10 and 16 s and were used over a period of 2 months with a good reproducibility. The sensors were applied successfully to determine DPH in pharmaceutical preparations and biological fluids. The results are compared with the official method. 相似文献