抗癌药物的电化学研究(Ⅱ)道诺霉素在DNA修饰石墨粉末微电极上的电化学行为及分析应用

研究了道诺霉素 ( DNM)在石墨粉末微电极和 DNA修饰石墨粉末微电极上的电化学行为 ,并分析了产生差别的原因。在此基础上 ,提出了测定微量 DNM的方法 ,DNM浓度在 1 .0× 1 0 - 7～ 1 .0× 1 0 - 5mol/L之间其微分脉冲伏安 ( DPV)峰电流与浓度有良好的线性关系 ,检出限为 5 .0× 1 0 - 8mol/L。采用标准加入法测定了模拟样品中的 DNM,回收率在 94%～ 1 0 8%之间 ,结果令人满意     

Determination of fluoride in complex liquid matrices by electrothermal atomic absorption spectrometry with in-furnace oxygen-assisted ashing

A new chemical method is reported for the determination of total fluoride in complex liquids and suspensions, such as fruit juices, urine, serum and blood. It is based on the formation of the A1F radical in a graphite furnace afterin situ oxygen-assisted ashing of the untreated sample. The absorbance of this radical is measured at 227.45 nm. The method is relatively easy to use and provides a low detection limit (14 ng/ml) and reasonable reproducibility (5–10%).     

Determination of mercury in soils and sediments by graphite furnace atomic absorption spectrometry with slurry sampling

A graphite furnace atomic absorption spectrometric procedure for the determination of mercury is presented, in which the samples are suspended in a solution containing hydrofluoric and nitric acids. Silver nitrate (4% m/v) and potassium permanganate (3%) are incorporated, in the order specified, and aliquots are directly introduced into the graphite furnace. A fast heating programme with no conventional pyrolysis step is used. The detection limit for mercury in a 125 mg ml⁻¹ suspension is 0.1 μg g⁻¹. Calibration is performed by using aqueous standards. The reliability of the procedure is proved by analysing certified reference materials.     

Coprecipitation with metal hydroxides for the determination of beryllium in seawater by graphite furnace atomic absorption spectrometry

Coprecipitation first with magnesium hydroxide, next with tin(IV) hydroxide is developed for the determination of traces of beryllium in sea-water. To a 200-ml sample is added a sodium hydroxide solution to form magnesium hydroxide at pH 11.5, on which beryllium is quantitatively coprecipitated. The precipitate is separated by centrifugation and dissolved in 2 ml of 12 mol/l hydrochloric acid. The resulting solution (ca. 10 ml) is mixed with 2 mg of tin (IV) carrier and the pH is adjusted to 5.0 to collect the beryllium on tin (IV) hydroxide, leaving magnesium ions in the solution. The tin (IV) hydroxide is centrifuged, dissolved in 0.1 ml of 5 mol/l hydrobromic acid, and then diluted to 1 ml with water. Magnesium is so added as to be 500 g/ml for increasing the sensitivity about four times, and the beryllium in the solution is determined by graphite furnace atomic absorption spectrometry. The experiments with synthetic seawater samples showed that pg — g amounts of beryllium can be coprecipitated on the metal hydroxides and beryllium at the low ng/1 level can be determined with reasonable precision (RSD < 10%). The detection limit of the proposed method is 0.5 ng/l of beryllium in seawater.     

Corrugated single-layer graphite sheet as a model of stepped surface of a crystal

Electronic structure calculations have been performed for flat graphite sheets and periodically distorted sheets with different values of deformation angle and hydrogen adsorption. These characteristics do not all behave monotonically with increasing deformation angle. At small deformation angles, the electrons pass from the atoms of terraces to those of edges, while at larger angles the reverse pattern is observed. The position of the Fermi level also varies nonmonotonically. The binding energy of hydrogen depends significantly on the adsorption site, and the difference can be doubled. Based on the ata obtained, it was concluded that a priori statements derived from the “general concepts” on the difference in the physicochemical properties of, for example, terrace and edge atoms on high-index facets are unreliable.     

石墨炉原子吸收法中热解涂层石墨管在无标准分析法测定环境样品中铬的应用

本文探讨了热解涂层石墨管测定铬的最佳实验条件,研究了各种酸和干扰物质的基体效应,提出用浓氨水为基体改进剂克服高氯酸的干扰。比较了各原子化温度时的理论和实验特征量。使热解涂层石墨管有可能用于无标准分析法测定各种环境样品中的铬。     

Nafion化学修饰圆盘预富集-石墨炉 原子吸收联用法对牛血超氧化物歧化酶中铜、锌分布状态的研究

本文研究了Nafion化学修饰钨丝圆盘预富集-石墨炉原子吸收(GFAAS)方法测定牛血超氧化物歧化酶(SOD)中游离态Cu～(2+)及Zn～(2+)的方法,并用GFAAS法直接测定SOD中铜、锌的总量,证实了牛血SOD中金属辅基铜、锌原子个数比为1:1,初步探讨了一定浓度的牛血SOD中Cu～(2+)、Zn～(2+)的表观离解平衡常数。为提高SOD的活性和稳定性的研究,提供了一种有效的方法。     

石墨炉原子吸收法测定生物样品中镉的几种基体改进剂的比较

本文比较了磷酸二氢铵、氟化铵、硫酸铵、氯化钯、氯铂酸以及氯铂酸与多种有机酸的混合试剂在测定ＧＢＷ猪肝标准物质中镉时基体改进效果，其中，氯铂酸的基体改进能力最强，猪肝标准物质的回收率在９０％     

蒙脱石-石墨-聚氯乙烯复合电极测定制药废水中苯酚

报道了当制药废水PH8．0时，用蒙脱石－石墨－聚氯乙烯复合电极可以直接测定苯酚的含量而不受水杨酸存在的干扰，苯酚浓度在1．0μg/mL-25.0μg/mL范围内峰电流与浓度有良好的线性关系，I＝1．262c-0.046，相关系数r=0.998，检出限为0．1μg/mL，用该方法测定模拟制药废水中苯酚，其平均回收率为101．7％。     

Surface film formation on a graphite electrode in Li‐ion batteries: AFM and XPS study

The formation of a passivation film (solid electrolyte interphase, SEI) at the surface of the negative electrode of full LiCoO₂/graphite lithium‐ion cells using LiPF₆ (1M ) in carbonate solvents as electrolyte was investigated by means of x‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The analyses were carried out at different potentials of the first and the fifth cycles, showing the potential‐dependent character of the surface‐film species formation. These species were mainly identified as Li₂CO₃ up to 3.8 V and LiF up to 4.2 V. This study shows the formation of the SEI during charging and its partial dissolution during discharge. Copyright © 2005 John Wiley & Sons, Ltd.