改性Pd/C催化氢化蒎烯的研究

报道了Pd/C催化剂用于蒎烯氢化制蒎烷的研究结果 ,得到了氢化反应的适宜条件。重点考察了修饰剂对催化剂活性和选择性的影响。     

平台石墨炉原子吸收法直接测定全血中痕量锗

研究了基体改进及其用量，锗的灰化和原子化温度以及６种共存离子的干扰，采用锶和硝酸铵混合液作基体改进剂，锗的灵敏度高，提高了方法的选择性，样品不需消化与分离，可采用平台石墨炉法直接测定血样中的痕量锗。     

抗坏血酸作基体改进剂石墨炉原子吸收光谱法测水中铷

提出了以抗坏血酸作基体改进剂石墨炉原子吸收光谱测定水中铷的新方法.本法特征量为4.6pg Rb,检出限(3s)为 0.27μg·L~(-1)样品加标回收率为95%～110%.方法简便、快速、结果准确可靠.     

平台石墨炉原子吸收法直接测定高温镍基合金中硒

研究了基体改进剂及其用量,硒的灰化、原子化和出现温度,以及近20种共存离子的干扰。采用镍和钯混合液作基体改进剂,硒的灵敏度高,抗干扰能力强,不需要分离样品基体,可以采用平台石墨炉法直接测定高温镍基合金中硒。     

On the uniforming of the atomization process for inorganic and organic mercury in graphite furnace atomic absorption spectrometry

The analytical performance of Pd, Au, Rh, Ir and their mixtures used as chemical modifiers has been investigated for mercury determination by graphite furnace atomic absorption spectrometry. The aim of this work was to evaluate whether chemical modification assures uniform atomization of analyte independent of its chemical form; mercury was used for this study. The investigations were performed for mercury introduced in the form of inorganic Hg(II) or organic PhHg(I). The best conditions, i.e. maximum pyrolysis temperature (450 °C), lowest temperature for atomization (1100 °C), provided almost the same sensitivity for both forms of mercury when a thermally reduced mixed modifier composed of Pd/Rh was used. The accuracy of the selected conditions was evaluated by a recovery test for various natural waters.     

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.     

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%.     

Effect of Transition Element Ions on the Catalytic Activity of Titanium Dioxide during Chemical Deposition of Metallic Copper

We have established the high catalytic activity of TiO₂, modified by Pd²⁺, Cu²⁺, Fe³⁺, and Co²⁺ ions, in reduction of Cu²⁺ ions by formaldehyde in solution. We propose a likely scheme for the electronic processes that occur, including injection of electrons from the reducing agent into the conduction band and formation of metallic nanoparticles on the surface that effectively catalyze deposition of metallic copper.     

The determination of total Se in urine and serum by graphite furnace atomic absorption spectrometry using Ir as permanent modifier and in situ oxidation for complete trimethylselenonium recovery

The present work evaluated the use of iridium (Ir) as permanent modifier for the determination of total selenium in urine and serum by graphite furnace atomic absorption spectrometry. Concerning urine, the presence of trimethylselenonium (TMSe⁺) was especially considered. Pyrolysis and atomization temperatures of 1,000 and 2,100°C, respectively, were used. For nondigested urine and serum samples, 0.2% v/v HNO₃ and Triton X-100 were used as diluents, respectively, and the same initial platform Ir treatment was effective for up to 1,100 atomization cycles. Good precision [less than 5% relative standard deviation (RSD)] can be achieved with the proposed method. Low TMSe⁺ recovery was observed for nondigested urine samples. Thus, if this species is to be considered in urine analysis, a previous external mineralization step was found to be necessary. Alternatively, an in situ oxidation treatment was developed. Detection limits of 8, 10, and 7 μg l⁻¹ were obtained after dilution, microwave-assisted digestion, and in situ oxidation procedures, respectively. The accuracy of the method was validated by the analysis of certified reference or commercial quality control materials and spiked samples.     

Combined effect of organic modifier concentration and column temperature on retention in reversed-phase ion-pair liquid chromatography

Summary The retention behavior of phenylamine and naphthylamine sulphonic acid was evaluated in reversed-phase ion-pair liquid chromatography as a function of organic modifier concentration and column temperature. It has been observed that the logarithm of capacity factors decrease linearly with organic modifier concentration, and there is a good linear relationship between the intercept and slope for this relationship. Phenylamine and naphthylamine sulphonic acid retention decreases with increase in column temperature. A linear dependence of lnk _ip on the reciprocal of the absolute temperature, the Van't Hoff plot, was observed over the column temperature range studied, and the standard enhalpic change (H^o) for these sulphonic acid transfers from the mobile phaser to the stationary phase was determined. H^o was dependent on the solute structure and in the range from 2.5 Kcal/mol to 5.5 Kcal/mol, which is close to that observed in RP-HPLC. The enthalpy/entropy compensation effect was evaluated by plotting lnk _ip(T) vs. –H^o, and the apparent differences in retention mechanisms between the analytes were observed, which may arise from the significant differences in their configuration, hydrophobicity and the charges of the solutes as well as the complex retention processes of RP-IPC.