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821.
Keliana D. Santos 《Talanta》2010,80(5):1999-109
A boron-doped diamond (BDD) electrode was used for the electroanalytical determination of estriol hormone in a pharmaceutical product and a urine sample taken during pregnancy by square-wave voltammetry. The optimized experimental conditions were: (1) a supporting electrolyte solution of NaOH at a pH of 12.0, and (2) a frequency of 20 Hz, a pulse height of 30 mV and a scan increment of 2 mV (for the square-wave parameters). The analytical curve was linear in the concentration range of 2.0 × 10−7 to 2.0 × 10−5 mol L−1 (r = 0.9994), with a detection limit of 1.7 × 10−7 mol L−1 and quantification limit of 8.5 × 10−7 mol L−1. Recoveries of estriol were in the range of 98.6-101.0%, for the pharmaceutical sample, and 100.2-103.4% for the urine sample, indicating no significant matrix interference effects on the analytical results. The accuracy of the electroanalytical methodology proposed was compared to that of the radioimmunoassay method. The values for the relative error between the proposed and standard methods were −7.29% for the determination of estriol in the commercial product and −4.98% in a urine sample taken during pregnancy. The results obtained suggest a reliable and interesting alternative method for electroanalytical determination of estriol in pharmaceutical products and urine samples taken during pregnancy using a boron-doped diamond electrode. 相似文献
822.
We describe direct polymer attachment to hydrogen and deuterium-terminated diamond (HTD and DTD) surfaces using a radical initiator (di-tert-amyl peroxide, DTAP), a reactive monomer (styrene) and a crosslinking agent (divinylbenzene, DVB) to create polystyrene encapsulated diamond. Chemisorbed polystyrene is sulfonated with sulfuric acid in acetic acid. Surface changes were followed by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). Finally, both polystyrene-modified DTD and sulfonated styrene-modified DTD were used in solid phase extraction (SPE). Percent recovery and column capacity were investigated for both phenyl (polystyrene) and sulfonic acid treated polystyrene SPE columns. These diamond-based SPE supports are stable under basic conditions, which is not the case for silica-based SPE supports. 相似文献
823.
Isarita Martins Larissa de Souza Canaes Keity Margareth Doretto Susanne Rath 《Electroanalysis》2010,22(4):455-462
The applicability of boron‐doped diamond (BDD) as a working electrode in an amperometric cell, coupled to HPLC, was demonstrated, for determining benzodiazepines in pharmaceutical preparations. The separation of the benzodiazepines was achieved using a Waters XTerra RP18 column (250×4.6 mm, 5 μm) with a mobile phase sodium phosphate (pH 3.5; 0.10 mol L?1)‐acetonitrile (65 : 35, v/v) at flow of 1.2 mL min?1. The measurements were performed in a system 871 Advanced Bioscan (Metrohm) with a BDD (8000 ppm) adapted to the thin layer mode cell. Stainless steel and platinum wire were used as reference and auxiliary electrodes, respectively. The cell was operated in pulse mode, using ?1.9 V as initial potential. The method presented linearity, repeatability and ruggedness and it represents a novel, alternative electroanalytical method for benzodiazepines determination. 相似文献
824.
K. Fabisiak M. Szreiber C. Uniszkiewicz T. Runka D. Kasprowicz 《Crystal Research and Technology》2010,45(2):167-172
Thin polycrystalline diamond films were synthesized on silicon substrate by Hot Filament Chemical Vapor Deposition (HF CVD) technique from a mixture of hydrogen and different content of methyl alcohol. A comparative study on the Electron Paramagnetic Resonance (EPR), Raman spectroscopy and Scanning Electron Microscopy (SEM) were performed. It was shown that EPR signal, Raman spectra and morphology, studied by SEM, strongly depend on the ratio of CH3OH/H2 in the HF CVD reactor. The peak‐to‐peak line‐width in EPR signal varies from 0.09 to 0.8 mT depending on diamond quality. The Raman spectra of our diamond film showed, except well defined diamond Raman lines positioned at 1332 cm‐1 with different Full Width at Half Maximum (FWHM), a broad band having maximum at around 1530 cm‐1 which is characteristic for amorphous carbon phase. The obtained results show that EPR, SEM and Raman spectroscopy yield complementary results about the defects present in CVD diamond films. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
825.
826.
山东蒙阴金刚石多晶的显微红外光谱研究及其成因意义 总被引:2,自引:0,他引:2
山东蒙阴金刚石多晶可划分为多角刻面状和浑圆状金刚石多晶两大类,它们的显微红外光谱研究结果表明,金刚石多晶中的氮含量较低,介于16.69~72.81μg.g-1之间,且同一金刚石多晶的不同金刚石晶粒(或部位)中的氮含量不相同;刻面状金刚石多晶均为ⅠaAB型,且A心的浓度大于B心的浓度。浑圆状金刚石多晶也多为ⅠaAB型,但具有更高浓度的B心,且存在少数同时包含单替代氮、A心和B心的浑圆状金刚石多晶;金刚石多晶不是在金刚石颗粒的成核阶段所形成的,而是在金刚石长大期间或金刚石颗粒形成后的某个特殊条件下聚集而成;山东蒙阴金刚石多晶可能形成于氮浓度较低的较深部地幔。同时,多角刻面状金刚石多晶的形成时间稍晚于金刚石单晶体,浑圆状金刚石多晶的形成时间明显早于金刚石单晶体。 相似文献
827.
采用高分辨透射电镜、紫外和可见光Raman光谱及循环伏安法研究了1000 ℃下退火不同时间的硼掺杂纳米金刚石薄膜的微结构和电化学性能. 结果表明,随退火时间的延长,薄膜中纳米金刚石晶粒尺寸逐渐减小.当退火时间为0.5 h时, 金刚石晶粒尺寸由未退火样品的约15 nm减小为约8 nm, 金刚石相含量增加;当退火时间为2.0 h时,金刚石晶粒减小为2—3 nm, 此时晶界增多,金刚石相含量减少;退火时间为2.5 h时纳米金刚石晶粒尺寸和金刚石相含量又略有上升.晶粒尺寸和金刚石相含量的变化表明薄膜在退火过程中发生了金刚石和非晶碳相的相互转变.可见光Raman光谱测试结果表明,不同退火时间下, G峰位置变化趋势与ID/IG值变化一致,说明薄膜内sp2碳团簇较大时, 非晶石墨相的有序化程度较高.退火0.5, 1.0, 1.5和2.0 h时, 电极表面进行准可逆电化学反应,而未退火和退火时间为2.5 h时电极表面进行不可逆电化学反应.退火有利于提高薄膜电极的传质效率, 退火0.5 h时薄膜电极的传质效率最高,催化氧化性能最好.较小的晶粒尺寸、 较高的金刚石相含量以及纳米金刚石晶粒的均匀分布有利于提高电极表面反应的可逆性和催化氧化性能. 相似文献
828.
829.
在室温条件下, 利用金刚石对顶砧超高压实验技术, 对液态的正庚烷进行了原位高压拉曼光谱研究, 采用红宝石荧光压标测压, 实验的最高压力为20.78 GPa。实验中发现, 当压力达到1.2 GPa左右时, 原本透明的样品腔内有小晶粒形成, 此时测量的拉曼谱上发现有许多新的拉曼峰出现。因此, 我们判断正庚烷在此压力下发生了一次相变; 当压力增加到3 GPa左右时, 在92.42 cm-1和2913.6 cm-1处又出现了2个新的拉曼峰, 并且拉曼频移随压力变化的曲线出现拐点, 我们推测在此压力下正庚烷可能又发生第二次相变; 当压力高于14.5 GPa时, 正庚烷发生了第三次压致相变; 而当压力介于7.5~14.5 GPa之间正庚烷处于两相共存的状态。我们给出了液体正庚烷在高压下的相变序列为: 液相-旋转相Ⅲ-旋转相Ⅳ-结晶相。该研究结果为进一步理解和研究其他正烷烃在高压下的结构、物理和化学特性提供了理论基础。 相似文献
830.
《Optimization》2012,61(7):895-917
Generalized geometric programming (GGP) problems occur frequently in engineering design and management, but most existing methods for solving GGP actually only consider continuous variables. This article presents a new branch-and-bound algorithm for globally solving GGP problems with discrete variables. For minimizing the problem, an equivalent monotonic optimization problem (P) with discrete variables is presented by exploiting the special structure of GGP. In the algorithm, the lower bounds are computed by solving ordinary linear programming problems that are derived via a linearization technique. In contrast to pure branch-and-bound methods, the algorithm can perform a domain reduction cut per iteration by using the monotonicity of problem (P), which can suppress the rapid growth of branching tree in the branch-and-bound search so that the performance of the algorithm is further improved. Computational results for several sample examples and small randomly generated problems are reported to vindicate our conclusions. 相似文献