Effect on silicon atomization of tungsten-assisted modification of atomic-absorption spectrometer graphite furnaces

The influence of a tungsten-assisted modification to a tubular graphite furnace in an atomic absorption spectrometer on the Si atomization signal characteristics is studied. A hypothesis is proposed that explains a shift of Si atomization peaks for the modified furnaces compared with the standard ones. Some advantages of the standard tubular graphite furnaces modified by tungsten and the prospects for their application are demonstrated. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 13–17, January–February, 2008.     

复合改性剂对氢氧化镁的表面改性研究

采用硬脂酸钠/油酸钠/聚乙二醇6 000复配表面活性剂为改性剂,对氢氧化镁进行改性研究.通过改性前后氢氧化镁粉体的吸油值及其在液体石蜡中的吸光度等性能来评价氢氧化镁的改性效果,从而确定最佳改性条件,同时采用红外谱图研究了表面改性分子与氢氧化镁表面的作用机理.正交实验结果表明,在表面改性剂的质量分数为9％,硬脂酸钠/油酸钠/聚乙二醇6 000的配料比为2：2：1（质量比）,改性温度为60℃,改性时间为100 min条件下制备的产品性能优良,在石蜡中分散性良好,红外光谱显示表面改性剂分子在氢氧化镁表面发生化学吸附.     

浅谈石灰改良膨胀土路基的施工工艺

简述了基底处理方法及结果检测,介绍了原状膨胀土及改良剂(石灰)的性质,对石灰改良膨胀土路基的几个主要控制要素进行了分析。     

Selectivity of amylose tris(3,5-dimethylphenyl-carbamate) chiral stationary phase as a function of its structure altered by changing concentration of ethanol or 2-propanol mobile-phase modifier

In a previous publication, solid-state NMR data showed that the structure of Chiralpak AD chiral stationary phase (CSP) was altered by changing the concentration of ethanol or 2-propanol modifier in the chromatographic mobile phase. This present paper reports the effect of the CSP structural change on chiral selectivity alpha. The enantiomers of a series of compounds were chromatographed using ethanol or 2-propanol in various concentrations as mobile-phase modifier and the alpha values were determined. Changes of alpha were observed for some enantiomeric pairs when ethanol and 2-propanol concentrations were varied. These data correlate with previous findings on the structural changes of the CSP. Not every enantiomeric pair showed changes in alpha as the alcohol concentration was varied, indicating that the chiral selectivity depends not only on the CSP's structure, but also on the structures of the analytes.     

禾草灵对映体在纤维素-三(3,5-二甲基苯基氨基甲酸酯)手性固定相上的拆分

将纤维素-三(3,5-二甲基苯基氨基甲酸酯)(CDMPC)涂敷于自制的球形氨丙基硅胶上,制备了手性固定相.在正相条件下,用高效液相色谱法在该固定相上直接拆分了农药禾草灵的外消旋体,并系统地选用了多种二元及三元流动相体系对样品进行拆分.实验结果表明,流动相中不同的醇类改性剂及其含量的不同对样品保留时间和立体选择性有不同程度的影响,选用异丙醇改性剂时样品的拆分效果较好,在三元流动相体系正己烷/异丙醇/乙醇中可以实现对禾草灵外消旋体快速有效的拆分.     

Determination of Total Selenium Content in Cereals and Bakery Products by Flow Injection Hydride Generation Graphite Furnace Atomic Absorption Spectrometry Applying in-situ Trapping on Iridium-Treated Graphite Platforms

A flow injection hydride generation graphite furnace atomic absorption spectrometric (FI-HG-GFAAS) method was applied to the determination of Se in Se-doped and undoped cereals and bakery products. For the purpose of doping, the soils used for the cultivation of the cereals were dosed with Se-doped foliar fertilizers. The samples were dissolved in a mixture of HNO₃ and H₂O₂ solutions using microwave-assisted digestion. The decomposition of H₂Se generated from the sample solutions and the trapping of elemental Se were performed at a temperature of 300°C on an Ir-pretreated integrated graphite platform of a transversally heated graphite atomizer (THGA). For release of the trapped Se within a fairly short atomization time (5s), an atomization temperature of 2200°C was observed to be optimal. The overall efficiency of hydride generation, transport and trapping was 86%.The upper limit of the linear dynamic range of calibration was 10µgL^–1, which corresponds to 0.5µgg^–1 for solid samples. Recovery of the samples spiked with Se^VI solutions was found to be 93±6% on average. The relative standard deviation of the determinations was less than 8%. The limit of detection was found to be 0.06µgL^–1, corresponding to 3ngg^–1 for solid samples. The accuracy of the method was verified with the use of IAEA-155 (whey powder) certified reference material. End-capped THGA tubes resulted in an extension of the linear calibration range compared to that of standard THGAs.The Se content in bakery products made of undoped cereals ranged from 7.7 to 68ngg^–1 (wet weight) in 18 samples, whereas the Se content of the corresponding cereals was found to be below 100ngg^–1 (wet weight). The Se level of cereals grown on soils treated with Se-doped fertilizers ranged from 128 to 1046ngg^–1 (wet weight), and it depended linearly on the Se concentration of the corresponding foliar fertilizer.     

Determination of Nickel and Palladium in Environmental Samples by Low Temperature ETV-ICP-OES Coupled with Liquid-liquid Extraction with Dimethylglyoxime as Both Extractant and Chemical Modifier

A novel method for the determination of nickel and palladium in environmental samples by low temperature ETV-ICP-OES with dimethylglyoxime(DMG)as both the extractant and chemical modifier has been developed.In this study,it was found that nickel and palladium can form complexes with dimethylglyoxime(0.05%,mass fraction)at pH 6.0 and can be extracted into chloroform quantitatively.The complexes can be evaporated into plasma at a suita-ble temperature(1400 ℃)for ICP-OES detection.Under the optimized conditions,the detection limits of nickel and palladium are 0.48 and 0.40 ng/mL,respectively,while the RSD values are separately 5.0% and 3.1%(ρ=50 ng/mL,n=7).The proposed method was applied to the determination of the target analytes in environmental samples with satisfactory results.     

Cloud point extraction for the determination of lead and cadmium in urine by graphite furnace atomic absorption spectrometry with multivariate optimization using Box–Behnken design

Cloud point extraction (CPE) is proposed as a pre-concentration procedure for the determination of Pb and Cd in undigested urine by graphite furnace atomic absorption spectrometry (GF AAS). Aliquots of 0.5 mL urine were acidified with HCl and the chelating agent ammonium O,O-diethyl dithiophosphate (DDTP) was added along with the non-ionic surfactant Triton X-114 at the optimized concentrations. Phase separation was achieved by heating the mixture to 50 °C for 15 min. The surfactant-rich phase was analyzed by GF AAS, employing the optimized pyrolysis temperatures of 900 °C for Pb and 800 °C for Cd, using a graphite tube with a platform treated with 500 μg Ru as permanent modifier. The reagent concentrations for CPE (HCl, DDTP and Triton X-114) were optimized using a Box–Behnken design. The response surfaces and the optimum values were very similar for aqueous solutions and for the urine samples, demonstrating that aqueous standards submitted to CPE could be used for calibration. Detection limits of 40 and 2 ng L^− 1 for Pb and Cd, respectively, were obtained along with an enhancement factor of 16 for both analytes. Three control urine samples were analyzed using this approach, and good agreement was obtained at a 95% statistical confidence level between the certified and determined values. Five real samples have also been analyzed before and after spiking with Pb and Cd, resulting in recoveries ranging from 97 to 118%.     

石墨炉原子吸收光谱法测定生物样品中微量锗

采用钼酸铵浸渍处理石墨管 ,研究了苯基荧光酮为螯合剂 ,四氯化碳为萃取剂 ,N ,N 二甲基甲酰胺 (DMF)为反萃取剂的萃取富集锗的新方法 ,用硝酸镍作为基体改进剂 ,石墨炉原子吸收光谱法直接测定各种生物样品中微量锗。方法绝对灵敏度 (1%吸收 )为 1.67× 10 - 11g ,相对标准偏差 3.5 4 %～ 6.15 % ,回收率为 96%～ 10 2 %