Studies on Liquid‐Liquid Extraction and Recovery of Bismuth(III) from Succinate Media Using 2‐Octylaminopyridine in Chloroform

A procedure is described for the liquid‐liquid extraction and recovery of bismuth(III) from succinate solution using 2‐octylaminopyridine (2‐OAP) as an extractant. The quantitative extraction of bismuth(III) occurs from 0.004 to 0.007 M sodium succinate solution of pH 2.5‐10 using 0.036 M 2‐OAP in chloroform. The extracted metal ion has been recovered by stripping with (3 × 10 mL) 0.5 M nitric acid. The log‐log plot of distribution ratio versus succinate concentration and distribution ratio versus 2‐OAP concentration gave slopes of 2.0 and 0.9, respectively, indicating a metal‐succinate ratio of 1:2 and a metal: 2‐OAP ratio of 1:1. The ion pair complex has a high distribution ratio in chloroform, while other solvents are poor. The extractants are stable towards prolonged acid contacts and there is no loss in its extraction efficiency even after recycling ten times. The extraction behaviour of some commonly associated metal ions, namely Ga(III), Cd(II), Zn(II), Cr(VI), Cu(II), Ba(II), Sb(III), Sn(IV), Tl(I) and Pb(II), has also been investigated. Based on partition data, conditions have been identified for attaining some separations of bismuth(III) from other metal ions; these conditions are extended for the recovery of pure bismuth from ore and alloys. Thermodynamic quantities for the extraction process were calculated.     

Determination of Trace Manganese by Square‐Wave Stripping Voltammetry

A novel method of determining trace manganese by square‐wave stripping voltammetry with simultaneous plating mercury electrode is described in this paper. Well‐defined stripping peaks of manganese are obtained in H₃BO₄‐NaOH buffer (pH 8.0) and peak currents are in good linear relationship with manganese concentrations in two ranges: from 0.36 nM to 36 nM and from 73 nM to 909 nM. The obtained detection limit is 0.18 nM and relative standard deviation is 2.3% (n=7) under a predeposition time of 90 s. This proposed method has been used for the determination of trace manganese in real plasma samples with satisfiable results and good matching with the results of graphite furnace atomic absorption spectrometry.     

Development of effervescence-assisted switchable polarity solvent homogeneous liquid-phase microextraction for the determination of permethrin and deltamethrin in water samples prior to gas chromatography–flame ionization detection

An effervescent tablet-assisted switchable polarity solvent–based homogeneous liquid-phase microextraction combined with gas chromatography with flame ionization detection has been conducted for the separation, preconcentration, and detection of permethrin and deltamethrin in the river water specimens. Triethylamine (TEA) was utilized as the switchable polarity solvent in this method. The switching process was carried out by the dissolution of an effervescent tablet including an effervescency agent (sodium carbonate) and a proton donor agent (citric acid). Changing the pH of the specimen solution enhanced the conversion of TEA into protonated triethylamine carbonate through the tablet that generated carbon dioxide bubbles in situ. Finally, the addition of sodium hydroxide changed the ionization state of TEA and separated the two phases. Influential factors in the extraction were investigated. According to optimal situations, the limit of detection and the limit of quantification were 0.16 and 0.5 μg L⁻¹ for permethrin and 0.03 and 0.1 μg L⁻¹ for deltamethrin, respectively. The preconcentration factor was 194 in river water samples and inter- and intra-day precision (relative standard deviation %; n = 5) was <5%. The extraction recovery was obtained in the range of 93.0%–97% for permethrin and deltamethrin in water samples.     

Exact meta-analysis of several independent progressively type-II censored data

Exact inference for the case when multiple independent progressively Type-II censored samples are pooled is considered. Two representations for the marginal distributions of the resulting pooled order statistics are given, a direct method and an iterative method. The coverage probabilities and expected widths of exact nonparametric confidence intervals for quantiles are compared for various scenarios with one or more independent samples.     

Vortex‐assisted liquid–liquid micro‐extraction and high‐performance liquid chromatography for a higher sensitivity methyl methacrylate determination in biological matrices

A vortex‐assisted liquid–liquid micro‐extraction coupled with high‐performance liquid chromatography, with UV–vis, is proposed to pre‐concentrate methyl methacrylate and to improve separation in biological matrices. The use of 1‐octanol as extracting phase, its volume, the need for a dispersant agent, the agitation conditions and the cooling time before phase separation were evaluated. In optimum conditions, enrichment factors of 20 (±0.5) and enrichment recovery of 99% were obtained. The straightforward association of this extraction process with the HPLC method, previously regulated by the International Organization for Standardization, afforded a detection limit of 122 ng/mL and a quantification limit of 370 ng/mL. The within‐batch precision, relative standard deviation, was 3% for a sample with 1.49 µg/mL and 4% for a sample with 13.4 µg/mL. The results showed a between batch‐precision of 21% for experiments performed on five different days, for a sample with a concentration of 1.10 µg/mL in methyl methacrylate. Copyright © 2013 John Wiley & Sons, Ltd.     

用于计算机配色的反射光谱数据质量评估方法研究

基础色样的反射光谱数据质量是影响计算机配色结果的重要因素之一。目前评价配色反射光谱数据质量的方法有反射光谱检测法和K/S检测法,但这两种方法需检测每种基础色样和各个波长的反射率与K/S值,检测过程过于复杂,故不适用于光谱数据质量的快速直观检测。本文使用45°/0°和d/8°几何条件的分光光度计测量以铜版纸和银卡纸为基材的胶印油墨基础色样反射光谱数据,基于光谱检测法优化获取基础色样反射光谱数据的几何条件,提出了一种明度色度对比检测法；并对比分析了反射光谱检测法,K/S检测法和明度色度对比检测法。结果表明,45°/0°和 d/8°几何条件均可用于铜版纸基础色样反射光谱数据的测量,但45°/0°几何条件不符合银卡纸基础色样反射光谱数据的测量要求；而对于d/8°分光光度计,在包含镜面反射时,银卡纸为基材的透明白反射率小于各基色墨反射率,且青墨与品红墨反射率分别在浓度为60%开始出现异常交叉,从而导致高浓度区域光谱质量较差；而在明度色度对比检测图中,青墨与品红墨样条与参考铜版纸基础数据偏离更加明显。故须选择大于或等于各基色墨反射率的透明白,基础色样中需约束青墨与品红墨的最大浓度；以漫反射特性较好的铜版纸作为配色基材时,明度色度对比检测法检测效果较现有两种检测法更为直观。     

Crown Ether/Carbon Nanotubes Based Biperiden Disposable Potentiometric Sensor

Sensitive disposable sensors have been constructed for potentiometric determination of Biperiden hydrochloride (BPHCl) based on multi‐walled carbon nanotubes–polyvinylchloride (MWNTs–PVC) composite in presence of dibenzo 24‐crown‐8‐ ether as a molecular receptor. Electrode matrix composition was optimized on the basis of the nature of the electroactive material, ionic sites, membrane plasticizer, and nanomaterial. The fabricated sensors showed improved selectivity and sensitivity towards biperiden hydrochloride with Nernstian cationic compliance of 59.8±1.1 mV decade⁻¹ in the concentration range from 10⁻⁶ to 10⁻² mol L⁻¹. Modification with carbon nanotubes promote electron‐transfer processes and enhanced the stability of potential reading, response time and shelf lifetime of sensors. The proposed method was applied for potentiometric assay of BPHCl in dosage formulation and biological fluids under batch and flow injection analysis (FIA) with average recoveries agreeable with the reported official methods.     

Strategy for the separation of concentrated samples by capillary electrophoresis

The use of concentrated samples is usually avoided during conventional separations since utilization of concentrated samples normally compromises the quality of separation. However, in case of the detection of low‐abundance components, highly concentrated samples are necessary, which leads to an extremely high concentration for high‐abundant components. This will make the separation difficult due to the serious longitudinal dispersion. Here, we developed a method to separate high concentration of components based on the modified capillary electrophoresis. The mechanism involves concentrated sample stretched into a wider zone in the higher electric field strength; the sample zone is fractionated into thin sections via a cutting effect; these thin sections are then separated. Based on this mechanism, we examined to separate an overloaded mixture of N ,N ′‐diphenylguanidine and N ,N ′‐di(o‐tolyl)guanidine. Baseline separation was achieved due to much small longitudinal dispersion. The theoretical plate numbers of peaks were around 3.5 × 10⁵ m⁻¹. The practicality of the new approach is demonstrated in the separation of a model protein mixture, containing lysozyme, bovine serum albumin, and ribonuclease A.     

Ultrasound-assisted emulsification microextraction method based on applying low density organic solvents followed by gas chromatography analysis for the determination of polycyclic aromatic hydrocarbons in water samples

In this study, a fast, simple and efficient ultrasound-assisted emulsification microextraction (USAEME) method was successfully developed based on applying low density organic solvents. Fourteen microliters of toluene was injected slowly into a 12 mL home-designed centrifuge glass vial containing an aqueous sample that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and 2 μL of separated toluene (about 4 μL) was injected into a gas chromatographic system equipped with a flame ionization detector (GC-FID) for analysis. Some polycyclic aromatic hydrocarbons (PAHs) were selected as model compounds for developing the method and evaluating its performance and to compare the efficiency of the proposed method with previously reported techniques. Several factors influencing the emulsification, extraction and collection efficiency such as the nature and volume of organic solvent, emulsification–extraction temperature, ionic strength and equilibrium and centrifugation times were investigated and optimized. Under the optimum conditions, preconcentration factors (PFs) in a range of 1776–2714 were obtained. The performance of the proposed method was studied in terms of linear dynamic range (LDRs from 0.05 to 100 μg L⁻¹), linearity (R² ≥ 0.994), precision (repeatability: RSD% ≤ 7.9, reproducibility: RSD% ≤ 14.6) and extraction percents (59.2–90.5%). Limits of detection (LODs) in the range of 0.02–0.05 μg L⁻¹ were obtained for different PAHs. The applicability of the proposed method was evaluated by the extraction and determination of PAHs from several natural water samples.