Potential use of capillary zone electrophoresis in size characterization of quantum dots for environmental studies

Quantum dot (QD) nanoparticles (NPs) are of great interest to various researchers due to their wide range of applications, from photovoltaic sensitizers to in vivo fluorescent probes. There is a need to characterize environmental fate, degradation, and ecotoxicity of QDs because these NPs may be introduced into the environment upon disposal of waste products containing QDs following the anticipated increase in their production and use. Because the properties of QDs are defined primarily by their composition and size, it is imperative that QD size be measured accurately and quickly. Current methods for measuring the size of QDs tend to be relatively slow, require large amounts of sample and may not be suitable for environmental or biological samples. Capillary zone electrophoresis (CZE), with its inherently high separation efficiency based on the size-to-charge ratio of analytes, holds promise for efficient size determination of NPs in aqueous samples.This review examines the potential use of CZE in characterizing and separating QDs compared to the conventional methods employed in determining size distribution of NPs. We briefly discuss the advantages and the limitations of commonly used techniques for size characterization.In addition to published literature, we present results from our laboratory using CZE with laser-induced fluorescence (LIF) to examine the effect of natural organic matter and buffer composition on the electrophoretic mobility of QDs. The use of CZE in environmental studies can provide insights into the degradation and the potential impacts of QDs upon exposure to environmental and biological matrices.     

Spectrophotometric study of complex formations between 1-(2-pyridylazo)-2-naphthol (PAN) and some metal ions in organic solvents and the determination of thermodynamic parameters

The complexation reactions between Ni(2+), Co(2+) and Zn(2+) metal ions with PAN in methanol (MeOH), acetonitrile (AN) and dimethyl sulfoxide (DMSO) were studied using a spectrophotometric method. The stability constants of the resulting complexes were determined from computer fitting absorbance mole-ratio data. The results revealed that the stability constants of complexes are varying in order of Ni(2+)相似文献   

溴酸钾氧化孔雀石绿和甲基橙褪色光度法测定水中亚硝酸根

在H3PO4介质中,利用痕量NO2-催化KBrO3氧化孔雀石绿和甲基橙褪色的反应,建立了双波长双指示剂催化动力学光度法测定痕量NO2-的新方法。该反应在最大吸收峰505nm和615nm处,催化和非催化体系吸光度的变化与NO2-浓度呈线性关系,线性范围为0.01～0.80μg/mL,检出限为1.3×10-3μg/mL,该方法用于环境水样(自来水、雨水、延安卷烟厂废水)中痕量NO2-的测定,加标回收率为97%～110.2%.     

1-(2-噻唑)-3-(8-(5-对磺酸基苯基偶氮)喹啉)-三氮烯的合成及其与铜(Ⅱ)的显色反应

合成了新试剂1-(2-噻唑)-3-(8-(5-对磺酸基苯基偶氮)喹啉-三氮烯(TCPQT),并研究了其与Cu2+的显色反应。结果表明:在pH 7.5的磷酸盐缓冲溶液中,TCPQT与Cu2+形成摩尔比为1:1的紫红色络合物,该络合物在606.5nm处有一最大吸收峰,其表观摩尔吸光系数为3.36×105L.mol-1.cm-1,Cu2+的质量浓度在0～0.4μg/mL范围内符合比尔定律,相关系数r=0.9993。方法已用于测定食品中的微量铜。     

Rapid and simultaneous determination of imidazolium and pyridinium ionic liquid cations by ion-pair chromatography using a monolithic column

A method for rapid and simultaneous determination of imidazolium and pyridinium ionic liquid cations by ion-pair chromatography with ultraviolet detection was developed.Chromatographic separations were performed on a reversed-phase silica-based monolithic column using 1-heptanesulfonic acid sodium-acetonitrile as mobile phase.The effects of ion-pair reagent and acetonitrile concentration on retention of the cations were investigated.The retention times of the cations accord with carbon number rule.The method has been successfully applied to the determination of four ionic liquids synthesized by organic chemistry laboratory.     

二甲酚橙-溴酸钾体系催化动力学光度法测定微量甲醛

在硫酸介质中,溴酸钾在甲醛的催化作用下能氧化二甲酚橙褪色,其褪色程度与甲醛含量成正比,从而建立了光度法测定微量甲醛的新方法。方法的最大吸收波长为435 nm,在50℃水浴中反应10 min,甲醛含量在0～20μg/mL内呈线性关系。方法应用于废水中微量甲醛的测定,相对标准偏差为4.34%,回收率在91.0%～102.8%之间。     

Spectrophotometric,potentiometric, and conductometric studies of binary complex formation between copper(II) and three forms of vitamin B6 in aqueous solutions

This article reports the detailed study concerning the mode of binding of three forms of vitamin B₆, pyridoxamine (pm), pyridoxine (pn), and pyridoxal (pl), with Cu(II) in aqueous solutions using three independent methods: potentiometry, conductometry, and UV–vis spectroscopy. The stability constants of complexes formed between copper(II) and vitamin B₆ were investigated by potentiometric titration in 0.1 M KNO₃ ionic medium at 25 °C. While drawing the relations between molar conductance and the ratio of metal to ligand concentrations, different types of lines were obtained indicating the formation of 1 : 1 and 1 : 2 stoichiometric compounds. The stability constants have been determined using EQUID and CVEQUID computer programs and the obtained results were in agreement. The relatively high values of stability constants of Cu(II)-vitamin B₆ complexes obtained from three independent methods in comparison to those with other competing cations suggest that the complexes studied are relatively stable in aqueous solutions.     

Chloro complexes of cobalt(II) in aprotic solvents: stability and structural modifications due to solvent effect

Cobalt(II) chloro complexes were studied in aprotic solvents, namely, dimethylsulfoxide (DMSO), dimethylformamide (DMF), and propylene carbonate (PC). The measurements were performed spectrophotometrically in UV–visible–IR region at 25°C and at constant ionic strength: I = 1 mol L^?1 in DMSO and DMF, and 0.1 mol L^?1 in PC. Different models were tested and the model 1 Elleb, M, Meullemeestre, J, Schwing, MJ and Vierling, F. 1980. Inorg. Chem., 19: 2699[Crossref], [Web of Science ®] , [Google Scholar], 2 Elleb, M, Meullemeestre, J, Schwing, MJ and Vierling, F. 1982. Inorg. Chem., 21: 1477[Crossref], [Web of Science ®] , [Google Scholar], 3 Khan, MA, Meullemeestre, J, Schwing, MJ and Vierling, F. 1983. Polyhedron, 2: 459[Crossref], [Web of Science ®] , [Google Scholar], 4 Amuli, C, Meullemeestre, J, Schwing, MJ and Vierling, F. 1983. Inorg. Chem., 22: 3567[Crossref], [Web of Science ®] , [Google Scholar], i.e., that of four mononuclear successive complexes was retained. Stability constants of the identified complexes were determined and they increase inversely with the Gutmann's donor number of the solvents. Calculated electronic spectra are reported and the effect of solvents on the spectral properties are discussed. The symmetry of tetrachlorocobaltate is strictly T_d.     

Spectrophotometric Determination of Iron(III) as Azide Complexes in Aqueous Tetrahydrofuran

Abstract

A simple, sensitive and alternative method for the spectrophotometric determination of iron(III) has been established. The procedure is based on the formation of iron-azide complexes in 60% (v/v) tetrahydrofuran/ water medium. The high sensitivity obtained in this method is due to the use of an interesting absorption band not previously reported in the literature. In the recommended conditions, absorbances for the ferric complexes are measured at 400 nm where the molar absorptivity is 1.52 × 10⁴ 1 mol^?1 cm^?1. The organic solvent used increases the sensitivity and the stability of the measurements. The precision is shown by the average deviation of about 0.3%. This system obeys Beer's law and is suitable for iron(III) determination in the concentration range from 0.6 to 3.2 mg 1^?1 (ppm). The best experimental conditions were determined studying the different factors involved. The influence of various diverse ions was also studied.     

Determination of Traces Of Bismuth in Water with Polyurethane Foak Thin-Layer Spectrophotometry

Abstract

A method for the spectrophotometric determination of bismuth is described. The method is based on using polyether polyurethane foam sorbent as a favourable matrix. Sorption of the bismuth iodide complex into the foam thin layer contributed into substantial improvement of the measured absorbance value of the coloured species. In this way quite satisfactory results were achieved, the average recovery amounts to 105.25%.