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161.
A new simple, rapid and sensitive spectrophotometric flow injection method for the determination of trace iodide is described
based on an ion associate of iodate (IO3
–) with 2- (3,5-dibromo-2-pyridylazo)-5-diethylamino-phenol (3,5-Br2-PADAP) and thiocyanate (SCN–). In a strongly acidic medium, this unstable violet product was formed with an absorption maximum at 605 nm. Flow injection
is an ideal method to reproducibly monitor the transient signal. Various parameters were optimized using the Super Modified
Controlled Weighted Centroid Simplex Method (SMCWC). Under the optimum experimental conditions, iodide could be determined
in the range of 1.00 × 10–6 and 2.4 × 10–5 mol l–1. The correlation coefficient of the calibration curve is 0.9991. With a sampling frequency of 80 h–1, the detection limit for iodide is 5.0 × 10–7 mol l–1. The proposed method has been applied to the determination of trace iodide after oxidizing I– in table salt or laver to IO3
–. In addition, the mechanisms of the ion association reaction was studied.
Received: 15 August 1996 / Revised: 10 October 1996 / Accepted: 16 October 1996 相似文献
162.
A method has been described for the direct determinations of trace cadmium using derivative atom trapping flame atomic absorption spectrometry with an improved water-cooled stainless steel trapping equipment. The characteristic concentration (gave a derivative absorbance of 0.0044) and detection limit (3sigma) of cadmium were 0.028 and 0.02 ng ml(-1) when collecting for a 1 min, respectively, which were 992 and 145-fold better than those of the conventional flame atomic absorption spectrometry. The detection limit and sensitivity of the proposed method for a 2 min collection time were 1 and 2 orders of magnitude higher than those of conventional flame atomic absorption spectrometry. The present method was applied to the determinations of cadmium in water samples with a recovery range of 91 approximately 111% and a relative standard deviation of 4.7 approximately 5.6%. 相似文献
163.
Direct determination of brucine by square wave voltammetry on 4-amino-2-mercaptopyrimidine self-assembled monolayer gold electrode 总被引:1,自引:0,他引:1
4-Amino-2-mercaptopyrimidine self-assembled monolayer (AMP SAMs/Au) was prepared on a gold electrode. The AMP SAMs/Au was characterized by using attenuated total reflection-fourier transform infrared (ATR-FTIR) and A.C. Impedance. The electrochemical behavior of brucine on AMP SAMs/Au was studied by cyclic voltammetry (CV) and square wave adsorptive stripping voltammetry (SWASV). The modified electrode showed an excellent electrocatalytic activity for the redox of brucine. The catalytic current increased linearly with the concentration of brucine in the range of 4.0 x 10(-7) to 2.0 x 10(-4) mol l(-1) by square wave voltammetry response. The detection limit was 6.0 x 10(-8) mol l(-1). 相似文献
164.
以正庚烷的转化为探针反应 ,研究了添加元素锆对铂重整催化剂性能的影响规律。结果表明 ,在 4 50℃和连续流动条件下 ,Pt/γ -Al2 O3催化剂中引入锆不仅能够提高铂催化剂的稳定性和芳构化产率、抑制氢解和异构化 ,而且能使铂催化剂保持初活性。锆含量在 0 .56%左右 ,其调变作用最为显著。 相似文献
165.
Two three-dimensional (3D) malonate bridged networks, [Cu(mal)(DMF)](n) (1) and [[Cu(mal)(0.5pyz)].H(2)O](n) (2), have been synthesized in H(2)O-DMF solution. Compound 1 exhibits ferromagnetic ordering below 2.6 K (T(c)), and 2 displays a metamagnetic behavior below 3.2 K (T(N)). 相似文献
166.
本文对优化液相色谱分离条件的重叠分辨率法进行了改进与扩展:首先利用全范围的二元线性梯度淋洗进行溶剂强度的优化,再通过重叠分辨率法进行了溶剂选择性的优化,并且建立了计算机系统,使此方法程序化。利用此方法建立了分离N-二茂铁甲酰基-N'-芳基硫脲类衍生物的最佳流动相体系。 相似文献
167.
The cyclic voltammetric behavior of carbon paste electrodes modified by direct admixing with the products of the reactions between ethanedial (glyoxal) and 5-amino-1,10-phenanthroline at 100°C and that of their iron(II) complexes is reported. The ligand(s) produced in absence of iron(II) are able to complex iron(II) and copper(II) ions reversibly, but other ions such as nickel(II), cobalt(II), cadmium(II) and manganese(II), if complexed, show no electrochemical activity. Admixing with the products of the reaction in the presence of excess of iron(II) ion, because of high insolubility and fast electron exchange, produces surfaces useful for amperometric detection in continuous-flow systems. The voltammetric and amperometric behavior in the presence of HSO?3 ions is reported in order to illustrate this application. 相似文献
168.
A C60-centered dendritic adduct with 12 symmetrically attached pyrene species was synthesized and found to have relatively simple fluorescence emission kinetics, in particular, the mono-exponential decay of the significant pyrene excimer emission. 相似文献
169.
Use of synchronous first-derivative fluorimetry for determination of gentamycin is described. Gentamycin reacts with acetylacetone and formaldehyde in pH 5.6 HOAc/NaOAc buffer solution to form N-gentamyl-2,6-dimethyl-3,5-diacethyl-1,4-dihydropyridine[I] which is a fluorescent substance. Spectra of [I] and the reagent blank can be separated with synchronous derivative fluorimetry, and gentamycin can be determined directly. The synchronous spectral peaks of [I] and the reagent blank are at 434 and 411 nm, respectively. The first-derivative peak of [I] is at 425 nm. Effects of pH, foreign ions, buffer system, and heating time on the determination of gentamycin have been examined. The linear regression equation of the calibration graph is C=0.0513H-0.0416, with a correlation coefficient of linear regression of 0.9978. C means total potency of gentamycin: U ml(-1); H means peak height in the linear regression equation calibration graph. The linear range for the determination of gentamycin is from 0.00 to 3.00 U ml(-1). Recovery is from 95.06 to 112.0%, R.S.D. of 3.8%. The results determined by the fluorimetric method agreed roughly with those by the microbiological method. The method is simple and has low detection limit. 相似文献
170.
Witzmann FA Bauer MD Fieno AM Grant RA Keough TW Kornguth SE Lacey MP Siegel FL Sun Y Wright LS Young RS Witten ML 《Electrophoresis》1999,20(18):3659-3669
We analyzed protein expression in the cytosolic fraction prepared from whole lung tissue in male Swiss-Webster mice exposed 1 h/day for seven days to aerosolized JP-8 jet fuel at concentrations of 1000 and 2500 mg/m3, simulating military occupational exposure. Lung cytosol samples were solubilized and separated via large scale, high resolution two-dimensional electrophoresis (2-DE) and gel patterns scanned, digitized and processed for statistical analysis. Significant quantitative and qualitative changes in tissue cytosol proteins resulted from jet fuel exposure. Several of the altered proteins were identified by peptide mass fingerprinting, confirmed by sequence tag analysis, and related to impaired protein synthetic machinery, toxic/metabolic stress and detoxification systems, ultrastructural damage, and functional responses to CO2 handling, acid-base homeostasis and fluid secretion. These results demonstrate a significant but comparatively moderate JP-8 effect on protein expression and corroborate previous morphological and biochemical evidence. Further molecular marker development and mechanistic inferences from these observations await proteomic analysis of whole tissue homogenates and other cell compartment, i.e., mitochondria, microsomes, and nuclei of lung and other targets. 相似文献