Field Enhanced Sample Injection for the CE Determination of Arsenic Compounds Using Successive Multiple Ionic Polymer Layer Coated Capillaries

A capillary electrophoresis method using indirect UV detection has been applied to the determination of arsenate [As(V)], arsenite [As(III)], monomethylarsonic acid and dimethylarsinic acid. The arsenic species were successfully separated in a successive multiple ionic polymer layer coated capillary. On-line sample preconcentration of arsenic compounds were performed by employing field enhanced sample injection. A baseline separation was achieved in a basic background solution of 10 mM 2,6-pyridinedicarboxylic acid at pH 10.3. The precision of migration time was 1.2–2.4% RSD and peak height was 8.1–12.9% RSD. The limits of detection at a S/N ratio of 3 for the four arsenic compounds were found to be 20–70 ppb, which are comparable to other on-line preconcentration techniques. The enhancement factor was improved by 230–1,500-fold.     

Factors Affecting the Performance of Capillary Isoelectric Focusing in Dynamically Coated Capillaries Using Polyethylene Oxide Polymer

Abstract

A simple, robust and reproducible capillary isoelectric focusing method using dynamically coated fused silica capillaries was developed. Simultaneous focusing and mobilization was successfully carried out using the hydrophilic polymer polyethylene oxide (PEO), which was added during sample preparation. The effects of preconditioning and anolyte and catholyte concentrations on the resolution and reproducibility of the method were optimized. Statistical screening of the significance of the effects of pressure, voltage, PEO concentration, and molecular weight on the efficiency of dynamic coating was carried out. Full-factorial design and analysis of variance (ANOVA) were used in order to determine the significance of each variable on the performance of the dynamic coat. Three response variables were selected to evaluate the method performance: migration time of a basic protein marker, migration time of an acidic protein marker, and difference in migration time between both markers. An empirically determined second order polynomial was employed to describe the relationship between the migration time and the isoelectric point under the experimental conditions studied in order to validate the method performance. The method was used under non-denaturing conditions to resolve a mixture of four standard proteins having isoelectric points covering a wide pH range (pH 3–11).     

An Ionic Molecular Glass as Electron Injection Layer for Efficient Polymer Light‐Emitting Diode

An ionic molecular glass based on a dendronized monoammonium salt has been facilely synthesized and utilized as an interfacial electron‐injection layer in a light‐emitting diode (LED). The characterization of a yellow‐green LED that involves an Al cathode and a thin layer of the new compound spin cast from a methanol solution has shown device performances comparable to those obtained with a Ba/Al cathode. Photovoltaic measurements under white light irradiation reveal that a thin layer of the new compound can significantly increase the built‐in potential and thus facilitate electron injection from an Al cathode. Furthermore, it is interesting to observe that the new ionic salt could undergo reorganization on the emissive conjugated polymer layer, which leads to the formation of nearly uniform nanoaggregates.

     

场放大进样-毛细管区带电泳法高灵敏检测三聚氰胺

建立了基于水塞联用场放大进样(FESI)的区带毛细管电泳(CZE)检测多种样品中三聚氰胺的分析方法。水塞组成为40%乙腈和60%水,水塞进入时间200 s,进水压力3 kPa。以120 mmol/L NaH2PO4缓冲液(pH 2.2)-10%甲醇为运行缓冲溶液,以0.10 mmol/L NaH2PO4(pH 2.2)-20%乙腈为样品基体溶液,进样电压20 kV,进样时间80 s,分离电压20 kV。在优化实验条件下,与普通的CZE法比较,三聚氰胺的紫外检测灵敏度提高了800倍,检出限(S/N=3)由2.0 mg/L降至2.5μg/L,线性范围为10～1 000μg/L。将该方法用于多种样品中三聚氰胺残留的检测,回收率为98%～106%,相对标准偏差(RSD,n=4)均不高于5.1%。该方法克服了紫外检测灵敏度低的缺陷,具有检测灵敏、简便易行、预处理简单、干扰少、经济环保和适用范围广等优点。     

Comparison of Sample Digestion Procedures for the Determination of Arsenic in Bottom Sediment Using Hydride Generation AAS

Certified reference materials (JMS-2 and JMS-1 – Marine sediment, LKSD-1 Lake Sediment, and STSD-1 Stream Sediment) and bottom sediment were analysed for arsenic by hydride generation atomic absorption spectrometry (HG-AAS) after digestion by different methods (microwave digestion, digestion in aluminium block, dry digestion) and different combinations of acids (HNO₃, HCl, HClO₄, H₂SO₄). The study revealed that both wet and dry digestion can be used to digest the reference materials and bottom sediment. Exceptionally satisfactory results were produced by the application of aqua regia, HNO₃ + HCl + HClO₄, and HNO₃ + HCl mixtures. Addition of Mg(NO₃)₂ during dry digestion caused an increase in arsenic recovery in the reference materials and improved the accuracy of arsenic determination in the bottom sediments.     

微波消解法测定化妆品中铅砷汞

化妆品在硝酸和过氧化氢溶液中 ,在微波电场的作用下 ,使分子产生高速的碰撞和摩擦而产生高热 ,在加压的条件下 ,由于酸的氧化及活性增加 ,可使化妆品在较短的时间内被消解 ,化妆品中铅砷汞以离子的状态存在于试液中。1　试验部分1.1　试剂与仪器氯化亚锡溶液 :2 0 0ｇ·Ｌ-1铅砷汞标准溶液的配制方法见ＧＢ7917.1.2 .3- 87ＭＫ Ⅱ型光纤压力自控微波溶样系统 ,6 0ｍｌ聚四氟乙烯消化罐 (上海新科微波技术应用研究所研制 )岛津ＡＡ 6 80 0型原子吸收光谱仪ＹＹＺ 2型冷原子测汞仪1.2　分析方法[1～ 3 ]称取均匀样品 0 .2～ 0 .5ｇ置于聚四氟…     

选用砷的189.0nm谱线改善氢化物发生原子吸收光谱法测定砷的分析性能

氢化物发生原子光谱法是测定微量砷的常用方法。由于砷的谱线发射强度低,分析线又位于紫外区,日常工作中必须采用很大的灯电流才能正常工作。但是灯电流太大会造成谱线变宽和自吸收,直接影响测定灵敏度、测定精密度和标准曲线的线性等主要分析性能。为了进一步提高砷灯的发射强度,人们在灯的发光机理方面进行了深入的研究［１～３］。本工作从改善砷的分析性能出发,在比较不同型号空心阴极灯谱线发射强度的基础上,着重考查了氢化物原子吸收法测定砷时Ａｓ１８９．０ｎｍ谱线的分析性能。１　仪器与试剂ＷＦＤＹ２型原子吸收分光光度…     

Ionic Organic Film Sensor for Determination of Phenolic Compounds

This paper describes the development of a new sensor based on an ionic organic film. The amphiphilic molecule, 4‐[(4‐decyloxyphenyl)‐ethynyl]‐1‐methylpyridinium iodide (10PyI), which has liquid‐crystalline properties, was synthesized and applied in the construction of a GCE/10PyI sensor. Analytical parameters for caffeic acid, repeatability (4.8 %), reproducibility (2.8 %), linearity (two ranges: 9.9×10^?7 to 3.8×10^?5 mol L^?1 and 4.7×10^?5 to 9.9×10^?5 mol L^?1) and detection limits (9.0×10^?7 mol L^?1 and 8.7×10^?6 mol L^?1), were determined. The method was successfully applied in the determination of total phenolic compounds (TPC) in mate herb extracts.     

Thin-Layer Chromatography of Polar and Ionic Compounds Using Active Gas Flow Over the Silica Gel Adsorbent Layer

JPC – Journal of Planar Chromatography – Modern TLC - Separation of polar and ionic substances in carbon dioxide and ammonia atmospheres on unmodified silica gel TLC plates with reduced...     

二乙基二硫代氨甲酸银体系流动注射法测定砷

本文设计了一种ＡｇＤＤＣ流动注射－分光光度法测定砷的系统。该系统采用自制的氢化物发生及吸装置，将液体流路和载气流路结合在一起。     

测定黄磷中砷方法的样品前处理的改进

标准方法(GB 7816-1998)测定黄磷中砷时,采用敞开式消解法预处理样品。实践表明该方法耗时,易引入污染,造成测定误差,而且稍有不慎易使黄磷自燃。作为改进,提出了回流冷凝消解法,即2~3 g试样于硝酸(3+2)溶液60 mL中,在160℃电热板上加热回流消解。消解完成后的试液按Ag-DDTC方法进行砷的测定。结果表明:回流冷凝消解法不仅避免了试样的自燃,而且大大缩短了试样消解时间,所测得砷结果的准确度达到原标准方法的水平。     

Ultrasonic Intensification of Sample Preparation for the Spectrophotometric Determination of Arsenic in Foodstuffs

A rapid procedure has been developed for the spectrophotometric determination of arsenic in various foodstuffs. The stimulating effect of ultrasound at the sample preparation stage has been found. The best parameters of ultrasound (frequencies from 22 to 40 kHz, intensity no less than 3.43 W/cm², treatment time 3 min) for the ultrasonic stimulation of digestion of some foodstuffs have been found.     

Separation and Determination of Amino Acids by CE Using 1-Butyl-3-methylimidazolium-Based Ionic Liquid as Background Electrolyte

Capillary electrophoresis using 1-butyl-3-methylimidazolium tetrafluoroborate as background electrolyte for the separation and determination of 11 amino acids was studied. Several parameters, such as ionic liquid concentration, pH of background electrolyte and applied voltage, were optimized. Amino acids were derived with Sanger’s reagent (2,4-dinitrofluorobenzene) and the detection was performed by an ultraviolet absorption detector at 360 nm. Under selected conditions, 11 amino acids were completely separated within 16 min. The RSD values of integrated areas and migration times are <3.03 and <1.64%, respectively. The electroosmotic flow can be influenced by imidazolium cation, and the association between the imidazolium cation and the derived amino acids plays an important role in the separation mechanism. This method not only provides an approach for the separation and determination of amino acids, but is also an extension of the ionic liquid application to capillary electrophoresis.     

The Use of Single Drop Microextraction and Field Amplified Sample Injection for CZE Determination of Homocysteine Thiolactone in Urine

Two cheap, simple and reproducible methods for the electrophoretic determination of homocysteine thiolactone (HTL) in human urine have been developed and validated. The first method utilizes off-line single drop microextraction (SDME), whereas the second one uses off-line SDME in combination with field amplified sample injection (FASI). The off-line SDME protocol consists of the following steps: urine dilution with 0.2 mol/L, pH 8.2 phosphate buffer (1:2, v/v), chloroform addition, drop formation and extraction of HTL. The pre-concentration of HTL inside a separation capillary was performed by FASI. For sample separation, the 0.1 mol/L pH 4.75 phosphate buffer served as the background electrolyte, and HTL was detected at 240 nm. A standard fused-silica capillary (effective length 55.5 cm, 75 μm id) and a separation voltage of 21 kV (~99 μA) were used. Electrophoretic separation was completed within 7 min, whereas the LOD and LOQ for HTL were 0.04 and 0.1 μmol/L urine, respectively. The calibration curve in urine was linear in the range of 0.1–0.5 μmol/L, with R² = 0.9991. The relative standard deviation of the points of the calibration curve varied from 2.4% to 14.9%. The intra- and inter-day precision and recovery were 6.4–10.2% (average 6.0% and 6.7%) and 94.9–102.7% (average 99.7% and 99.5%), respectively. The analytical procedure was successfully applied to the analysis of spiked urine samples obtained from apparently healthy volunteers.     

阻抗虚部计算聚合物电解质电导率

用交流阻抗法研究了（PEO1）10LiClO4-Al2O3和（PEO2）16LiClO4－碳酸乙烯酯（EC）两种复合物电解质体系的电导率，给出了等效电路和各拟合元件的物理意义。当阻抗谱图发生严重变形时，提出一种比较简单的计算聚合物电解质电导率的方法－－阻抗虚部最大值法。     

微波消解样品-蒸气发生-原子荧光光谱法测定石脑油中砷和汞

提出了微波消解样品-蒸气发生-原子荧光光谱法测定石脑油中砷和汞的方法.采用微波消解法处理样品,优化了微波消解条件和仪器工作条件,解决了消解液中过剩酸对测定的干扰.砷、汞的检出限分别为0.11,0.045 μg·L-1;线性范围分别在1.0～100.0,0.5～50.0 μg·L-1之间,砷和汞的相对标准偏差均小于4%,回收率分别在95.2%～97.2%,92.9%～95.2%之间.     

A Method for the Determination of Temperature inside Capillaries for Electrophoresis

Several researchers have addressed the problem of measuring the temperature inside the capillary. Terabe measured the outside temperature of the capillary with a micro thermocouple and found the temperature to be 70℃ at 25 kV for a 200 μm I.D. capillary. Unfortunately, the exact temperature was difficult to measure using Terabe's method because of an incomplete touch of the capillary with the micro thermocouple.     

HPLC Determination of Lactic Acid in Milrinone Injection and Oral Solution Using Ion-Exchange Sample Preparation Methods

Abstract

Lactic acid has been measured in Milrinone Injection and Oral Solution by HPLC using an ion-exclusion polymeric column coupled with a reversed-phase guard column. This dual-column chromato-graphy was preceded by classical ion-exchange sample preparation to eliminate interfering excipient components. The lactic acid lactate content of USP lactic acid was converted to lactic acid in processing. It was also further characterized using a TLC separation.     

离子液体单滴微萃取-高效液相色谱法测定水体中磺胺类药物

应用离子液体单滴微萃取(SDME)技术,建立了水体中7种磺胺类药物的高效液相色谱(HPLC)分析方法.考察了萃取剂种类与体积、萃取时间、搅拌速度、溶液pH值、盐浓度及萃取温度对萃取效率的影响.确定了最佳萃取条件为:利用9 μL-丁基-3-甲基咪唑六氟磷酸盐([C<,4MIM][PF<,6])离子液体作为萃取液滴,在搅拌...     

Large-Volume Sample Stacking with Polarity Switching in CE for Determination of Natural Polyphenols in Plant Extracts

A simple on-column preconcentration method for capillary electrophoretic determination of eight polyphenolic compounds (carnosic acid, cinnamic acid, caffeic acid and rosmarinic acid, quercetin, apigenin, luteolin and rutin) was devised. The method was applied for the assay of polyphenols in methanolic extract of the medicinal plant Orthosiphon Stamineus Benth. The analysis was carried out in fused silica capillaries (I.D. 50 μm, effective length 50 cm, total length 60 cm) with UV detection at 200 nm. The background electrolyte was 50 mM sodium tetraborate of pH 9.0 (adjusted with phosphoric acid). Large volume sample stacking with polarity switching was used for sensitivity enhancement. With sample injection representing 50% of capillary volume and polarity switching at 1.6 min, an average 90-fold enhancement of absorbance signal of the analytes was achieved. The calibration curves were linear (r = 0.9956–0.9994) in the range 0.2 to 1.8 μg mL^?1 of an analyte. The repeatability of migration times and peak areas was characterized by RSD values 0.11–0.57 and 1.63–5.66%, respectively. The proposed method offers favourable limits of detection (9–16 ng mL^?1) that compare well with those of LC.