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201.
建立了快速测定Pb(Ⅱ)的瑞利散射(RLS)新方法。在Tris-HCl缓冲介质中,溴化十六烷基三甲基铵(CTMAB)增敏溴甲酚绿(BCG),使瑞利散射显著增强,最大瑞利散射峰位于345nm,CTMAB-BCG进一步与Pb(Ⅱ)结合后生成的三元复合物的瑞利散射增强程度(|ΔIRLS|)与0.006~0.41mg/L范围Pb(Ⅱ)的质量浓度呈线性关系,定量限为0.053mg/kg。方法用于萝卜红色素中Pb(Ⅱ)的测定,回收率为98.5%~102%,相对标准偏差为1.8%~2.5%。 相似文献
202.
Ya-Nan WANG Pin MA Lu-Mei PENG Di ZHANG Yan-Yan FANG Xiao-Wen ZHOU Yuan LIN 《物理化学学报》2017,33(10):2099-2105
Lead acetate, which is highly soluble in dimethylformamide, was used to synthesize mixed halide perovskite CH3NH3PbBr3-xClx (MA = CH3NH3, 0 ≤ x ≤ 3) nanocrystals (NCs). This method provides an approach to address the low solubility of lead halides, especially lead chloride. Different Br/Cl ratios in MAPbBr3-xClx lead to various optical properties. The photoluminescence emission peak can be tuned from 399 to 527 nm. Their full-widths at half-maxima (FWHM) are about 20 nm. MAPbBr3-xClx NCs have an average diameter of ~(11 ± 3) nm and have uniform dispersion in toluene. The MAPbBr3 NCs have a long average recombination lifetime (τave = 97.4 ns) and a photoluminescence quantum yield (PLQY) of up to 73%. 相似文献
203.
Enrique Alvarez-Manzaneda Rachid ChahbounEsteban Alvarez Ramón Alvarez-ManzanedaPedro E. Muñoz Fermín JiménezHanane Bouanou 《Tetrahedron letters》2011,52(31):4017-4020
The treatment of 2,3-epoxy primary alcohols with lead(IV) acetate (LTA) leads to α-acetoxy aldehydes or α-acetoxy ketones, through the nucleophilic ring-opening of an intermediate oxonium and the subsequent carbon-carbon bond cleavage. This reaction represents a new route to optically active α-hydroxy carbonyl compounds. 相似文献
204.
Ines BaerJohannes van de Kreeke Thomas Peter Josef LinsingerPiotr Robouch Fernando Cordeiro RaposoBeatriz de la Calle 《Trends in analytical chemistry : TRAC》2011,30(7):1177
The International Measurement Evaluation Program (IMEP) organised the IMEP-24 interlaboratory comparison after reports in the media about high levels of lead in toys. The aim of this comparison was to verify the laboratories’ capacity to evaluate trace-element levels in a possible toy-like material according to the European Standard EN 71-3:1994. As test material, it used a former certified reference material containing levels of antimony, arsenic, barium, cadmium, chromium, mercury, lead and selenium around the limits set in the standard.Four expert laboratories confirmed the reference values (Xref) for all elements but Hg, and established a reference value for Hg. The scatter of the results reported by the participants was large, as expected, but showed a close to normal distribution around the reference values for five of the eight trace elements. The spread of results was mainly attributed to sampling and sample preparation.One major issue observed in this exercise was the lack of legislative rules about how to report the result, or, more specifically, the use of the analytical correction, which was introduced in EN 71-3:1994 to achieve consistent interpretation of results and which is to be applied when values are equal to or above the maximum limits set in the standard. Its application by the participants was very inconsistent and led to problems in their evaluation. There is clearly a need for clarification and for more formal regulations with regard to result reporting in order to minimise the risk of confusion.Participants were also asked to give their opinion with regard to the acceptability of the test material for the market. The majority correctly considered the material as non-compliant. However, almost one-third incorrectly assessed the material as compliant. 相似文献
205.
Ines BaerJohannes van de Kreeke Thomas Peter Josef LinsingerPiotr Robouch Fernando Cordeiro RaposoBeatriz de la Calle 《Trends in analytical chemistry : TRAC》2011,30(2):313-323
The International Measurement Evaluation Program (IMEP) organized the IMEP-24 interlaboratory comparison after reports in the media about high levels of lead in toys. The aim of this comparison was to verify the laboratories’ capacity to evaluate trace-element levels in a possible toy-like material according to the European Standard EN 71-3:1994. As test material, it used a former certified reference material containing levels of antimony, arsenic, barium, cadmium, chromium, mercury, lead and selenium around the limits set in the standard.Four expert laboratories confirmed the reference values (Xref) for all elements but Hg, and established a reference value for Hg. The scatter of the results reported by the participants was large, as expected, but showed a close to normal distribution around the reference values for five of the eight trace elements. The spread of results was mainly attributed to sampling and sample preparation.One major issue observed in this exercise was the lack of legislative rules about how to report the result, or, more specifically, the use of the analytical correction, which was introduced in EN 71-3:1994 to achieve consistent interpretation of results and which is to be applied when values are equal to or above the maximum limits set in the standard. Its application by the participants was very inconsistent and led to problems in their evaluation. There is clearly a need for clarification and for more formal regulations with regard to result reporting in order to minimize the risk of confusion.Participants were also asked to give their opinion with regard to the acceptability of the test material for the market. The majority correctly considered the material as non-compliant. However, almost one-third incorrectly assessed the material as compliant. 相似文献
206.
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208.
Shen Y Zhang Y Chen Y Li S Zhang Q Xie A 《Colloids and surfaces. B, Biointerfaces》2011,83(2):470-290
PbWO(4) crystals were readily synthesized by reacting lead oxide (PbO(2)) with sodium tungstate (Na(2)WO(4)·2H(2)O) at room temperature in the presence of tomato extract. Biomolecules such as vitamins, proteins in the extract played both the roles of reductant and template. The size and morphology of the PbWO(4) crystals could be controlled by adjusting the concentration of the reactants. When the concentration ratio of PbO(2) and Na(2)WO(4) was increased, the morphologies of the products varied from spherical to fusiform. Room-temperature fluorescence spectra indicated the products had a slight blue shift compared to the solid structure, which may be due to the structure defects in the crystals. The possible mechanism of PbWO(4) crystal growth in tomato extract was discussed. 相似文献
209.
Two novel coordination polymers, [Zn(dpc)(bmix)0.5]n ( 1 ), [Pb(dpc)(bmix)0.5]n ( 2 ), [dpc = dipicolinate, bmix = 1,4‐bis(2‐methylimidazole‐1‐ylmethyl)benzene], were hydrothermally synthesized and characterized by elemental analyses, IR spectroscopy, TGA, and X‐ray single crystal diffraction. In both complexes, the dipicolinate and bmix ligands act as spacers to link metal ions to give a 2D corrugated (6,3) network of 1 and a 3D microporous framework of 2 , respectively. The difference in the architectures is due to a diverging coordination mode of the carboxylate function. Furthermore, solid state fluorescence properties of the two complexes were investigated at room temperature. 相似文献
210.
Lindomar A. Portugal 《Microchemical Journal》2011,98(1):29-31
This paper proposes a method for the determination of lead in aluminum and magnesium antacids employing electrothermal atomic absorption spectrometry (ET AAS). The pyrolysis and atomization temperatures established during the optimization step were 700 and 2200 °C, respectively, using phosphate as the chemical modifier. Under these conditions, a characteristic mass of 25 pg, and limits of detection and quantification of 0.40 and 1.35 μg L−1, respectively were obtained. Some experiments demonstrated that the calibration can be performed employing the external calibration technique using aqueous standards. The precision expressed as relative standard deviation (RSD %) was 4.03% for an antacid sample with lead concentrations of 284.5 μg L−1. The proposed method was applied for the determination of lead in five antacid samples acquired in Salvador City, Brazil. The lead content was varied from 87 to 943 μg g−1. The samples were also analyzed after complete dissolution by inductively coupled plasma mass spectrometry (ICP-MS). No statistical difference was observed between the results obtained by both of the procedures performed. 相似文献