Ultramicro determination of organic halogens using sealed tube dry combustion method

A sealed tube dry combustion method that is simple, accurate, and precise for ultramicro determination of halogens in organic compounds has been developed. Samples below 1 mg are heated at 580 °C for 1 h in an electric furnace. After the combustion and absorption of the gaseous halogen, the interior of the tube is rinsed. Subsequent titration is carried out potentiometrically with silver nitrate and yielded standard deviations of 0.21% for chlorine, 0.17% for bromine, and 0.25% for iodine.     

衬钽管石墨炉原子吸收法测定痕量镓时基体改进剂的研究及应用

提出用钒和铜混合基体改进剂衬钽管石墨炉原子吸收测定镓的方法。衬钽管使镓的灵敏度提高6倍左右,钒和铜混合基体改进剂不仅能进一步提高灵敏度,而且能提高灰化温度,降低原子化温度,增强抗干扰能力。测定 GSD 标准样品中的镓时,不需对样品进行预分离即可直接进行测定,结果与参考值相符。     

Fused silica capillary tube isotachophoresis using a multichannel photodiode array detector

Isotachophoresis carried out in a 0.25 mm i.d. fused-silica capillary tube yielded high resolution, compared with that in a fluorinated ethylene-propylene polymer tube. The use of an ultraviolet-visible multichannel spectrophotometer with photodiode array as detector together with a cross flow cell (volume 0.01 μl) was investigated. The system was successfully applied to the analysis of cationic dyes such as neutral red, bismarck brown, and basic fuchsine.     

Determination of gallium by graphite furnace atomic absorption spectrometry with combined use of a tungsten-coated L'vov platform tube and a chemical modification technique

Tungsten-coated non-pyrolytic graphite (NPG), pyrolytic graphite (PG) and pyrolytic L'vov platform graphite (PPG) tubes were prepared, and their analytical performances were compared. The coating process simply involved injecting 100 μl of a sodium tungstate solution (0.01 mol l⁻¹) into each graphite tube, followed by heating according to a temperature programme similar to an atomisation cycle for the determination of gallium. This procedure for coating was repeated at least 12, 25, and 7 times towards NPG, PG, and PPG tubes, respectively. Among these tubes, the tungsten-coated PPG tube showed excellent performance for the determination of gallium. By combined use of a chemical modifier such as aluminium(III) or nickel(II) a detection limit (3σ) of 6 pg and sensitivity (1% absorption) of 3–4 pg were achieved. The practical potential of the proposed technique was demonstrated for the determination of gallium in several samples of alloys and fresh water.     

纳米科技研究中的若干新热点

讨论了纳米科技在各个领域不同于常规材料的优越性和它在各个范畴内的研究热点 ,了解它的发展趋势。     

热解涂层石墨管性能测试及其若干问题探讨

用石墨炉原子吸收光谱仪对国产热解涂层石墨管的使用寿命,灵敏度,精度等性能指标进行测试,并针对正常状态,原子化温度过高,载气不纯等几种不同条例下测试对石墨性能的影响进行了讨论,得出了对实际应用有参考价值的结论。测试时提界定较严格,选定典型的难熔金属元素Ｖ作为被测元素,有较强的代表性。     

用原子捕获技术提高火焰原子吸收光谱法的灵敏度

采用简易的石英原子捕获器，使Ｃｕ，Ａｇ，Ａｕ，Ｚｎ，Ｃｄ，Ｐｂ，Ｓｂ，Ｂｉ等易挥发元素在空气－乙炔火焰原子吸收光谱法中的灵敏度提高了３～５倍，并有较好的精密度，相对标准偏差在１％左右，方法中用此技术测定了标准物质中Ｐｂ、Ｃｄ的含量，获得了满意的结果，它较之石墨炉原子吸收光地具有快速，简便的特点，具有较大的实用价值。     

Ionic liquid‐based headspace in‐tube liquid‐phase microextraction coupled with CE for sensitive detection of phenols

An ionic liquid‐based headspace in‐tube liquid‐phase microextraction (IL‐HS‐ITLPME) in‐line coupled with CE is proposed. The method is capable of quantifying trace amounts of phenols in environmental water samples. In the newly developed method, simply by placing a capillary injected with ionic liquids (IL) in the HS above the aqueous sample, volatile phenols were extracted into the IL acceptor phase in the capillary. After extraction, electrophoresis of the phenols in the capillary was carried out. Extraction parameters such as the extraction time, extraction temperature, ionic strength, volume of the sample solution, and IL types were systematically investigated. Under the optimized conditions, enrichment factors for four phenols were from 1510 to 1985. The proposed method provided a good linearity, low limits of detection (below 5.0 ng/mL), and good repeatability of the extractions (RSDs below 6.7%, n = 6). This method was then utilized to analyze two real environmental samples of Xiaoxi Lake and tap water, obtaining acceptable recoveries and precisions. Compared with the usual HS‐ITLPME for CE, IL‐HS‐ITLPME‐CE is a simple, low cost, fast, and environmentally friendly preconcentration technique.     

Electrochemically controlled fiber‐in‐tube solid‐phase microextraction method for the determination of trace amounts of antipsychotic drugs in biological samples

In this study, a novel ‘fiber‐in‐tube’ configuration was applied to electrochemically controlled fiber‐in‐tube solid‐phase microextraction of antipsychotic drugs (perphenazine and chlorpromazine) from biological samples. To prepare an electrochemically controlled fiber‐in‐tube solid‐phase microextraction column, first eight stainless‐steel wires were placed into the stainless‐steel column. Then, a nanostructured Cu‐Cr‐Al ternary layered double hydroxide/polythiophene coating was prepared on the inner surface of the stainless‐steel tube and on the surfaces of the stainless‐steel wires by a facile in situ electrodeposition method. The nanostructured coating exhibited enhanced long lifetime, good mechanical stability, high porosity, and large specific surface area compared with polythiophene and Cu‐Cr‐Al layered double hydroxide coatings. Under the optimal conditions, the limits of detection were in the range of 0.07–0.8 μg/L. This method showed good linearity for perphenazine and chlorpromazine in the ranges of 0.3–300 and 0.2–300 μg/L, respectively, with coefficients of determination more than 0.9982. The inter‐ and intra‐assay precisions (RSD%, n = 3) were in the ranges of 3.0–5.1 and 2.5–4.5% at three concentration levels of 5, 25 and 50 μg/L, respectively. Finally, the method was applied for the analysis of the drugs in human urine and plasma samples.     

Measurement of bubble size distribution in protein foam fractionation column using capillary probe with photoelectric sensors

Bubble size is a key variable for predicting the ability to separate and concentrate proteins in a foam fraction ation process. It is used to characterize not only the bubble-specific interfacial a rea but also coalescence of bubbles in the foam phase. This article describes the development of a photoelectric method for measuring the bubble size distribution in both bubble and foam columns for concentrating proteins. The method uses a vacuum to withdraw a stream of gas-liquid dispersion from the bubble or foam column through a capillary tube with a funnel-shaped inlet. The resulting sample bubble cylinders are detected, and their lengths are calculated by using two pairs of infrared photoelectric sensors that are connected with a high-speed data acquisition system controlled by a microcomputer. The bubble size distributions in the bubble column 12 and 1 cm below the interface and in the foam phase 1 cm above the interface are obtained in a continuous foam fractionation process for concentrating ovalbumin. The effects of certain operating conditions such as the feed protein concentration, superficial gas velocity, liquid flow rate, and solution pH are investigated. The results may prove to be helpful in understanding the mechanisms controlling the foam fractionation of proteins.