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61.
Graphite arc emission spectrometry has become possible as a result of the invention of novel types of optical spectrometers
with Echelle-optics and semiconductor array detectors, and by the application of electronically controlled, high current arc
generators. An optimization of the excitation parameters to boron carbide analysis is reported here, measuring background
corrected line intensities that were integrated for the time of total evaporation of 5 mg boron carbide sample with or without
added chemical modifiers. The following set of experimental conditions were compared with respect of analytical sensitivity
and precision: (A) no modifier, Ar + O2 (20%), 16 A; (B) sample + graphite powder (1 + 1), Ar + O2 (20%), 16 A; (C) sample + CaF2 (1 + 1), Ar, 25 A; (D) sample + CaF2 + graphite powder (1 + 1 + 1), Ar, 25 A. The graphite powder modifier resulted in improved precision in general, and the
CaF2 was effective as a plasma ionization buffer and fluorinating agent. The best compromise was found under conditions B, when
oxygen was present in the discharge atmosphere. This is likely due to the stepwise conversion of the boron carbide matrix
to the more volatile boron oxide. Under conditions B, detection limits in the ranges of 0.3–9 μg g−1 for Al, Ca, Cr, Cu, Fe, Mg, Mn and Si and that of 18–38 μg g−1 for Ti, W, and Zr were attained. Average RSDs of 10.2 and 9.7% were found, respectively, without and with internal referencing
to boron. 相似文献
62.
Domínguez-González R Moreda-Piñeiro A Bermejo-Barrera A Bermejo-Barrera P 《Talanta》2005,66(4):937-942
A new method using diluted reagents (nitric and hydrochloric acids and oxygen peroxide) and ultrasound energy to assist metals acid leaching with from edible seaweed was optimized. The method uses a first sonication at high temperature with hydrochloric acid as a previous stage to an ultrasound-assisted acid leaching with 7 ml of an acid solution containing nitric acid, hydrochloric acid and hydrogen peroxide at concentrations of 3.7, 3.0 and 3.0 M, respectively. Optimum conditions for the first sonication step were ultrasound energy at 17 kHz, sonication temperature at 65 °C, an acid volume of 2 ml, an hydrochloric acid concentration of 6.0 M and a sonication time of 10 min. It has been found that the first sonication stage at high temperature with hydrochloric acid is necessary to obtain quantitative recoveries for As, Ba, Fe and V. Otherwise quantitative recoveries were reached for the other elements investigated (Ca, K, Na, Mg, Cd, Cr, Cu, Mn, Ni, Pb and Zn). The repeatability of the ultrasound-assisted acid leaching method was around 10% for all elements. Adequate limit of detection and limit of quantification were reached by using inductively coupled plasma-optical emission spectrometry (ICP-OES) for measurements. The method resulted accurate after analysing several seaweed certified reference materials (IAEA-140/TM, NIES-03 and NIES-09). The method was finally applied to the multi-element determination in edible seaweed samples. 相似文献
63.
The fast trace analysis method used to monitor 2,3,7,8-TCDD in stack gas during the incineration of the waste from Seveso is described. The sampling of volatile organic compounds from flue gases, distributed between all three aggregation states, is based on a micromethod developed for the trace analysis of water using a specially dimensioned adsorptive charcoal filter (1.5 mg charcoal). In conjunction with subsequent GC/MS measurements the rapid “fast cycle trace analysis” ensured specific 2,3,7,8-TCDD detection down to 100 pg per m3 flue gas in cycle times of about 1–2 hours. 相似文献
64.
65.
Effrosyni Zafeiraki Rastislav Sabo Konstantinos M. Kasiotis Kyriaki Machera Lucia Sabov Tom Majchrk 《Molecules (Basel, Switzerland)》2022,27(19)
Bees in search of diet sources intensively fly within a radius of up to 3 km, encountering nectar, pollen, and water sources which are potentially contaminated. Consequently, their products can provide valuable information about potential pollution. In the current study, 27 macro and trace elements, including the most hazardous ones, were measured in bees, honey, wax, pollen, and larvae, obtained from seven explicitly industrial areas in eastern regions of Slovakia, using a validated ICP-MS method. All the analysed elements were detected at least in one matrix. The detected concentrations of toxic elements, such as Hg, Pb, and Cd were in some cases higher in wax and bee samples, compared with honey, larvae, and pollen. In particular, Pb and Hg maximum concentrations were detected in the wax samples from Poša (3193 µg/kg) and Strážske_A (90 μg/kg). In addition, adult bees accumulated more elements than larvae, while wax and adult bees seemed more suitable for monitoring macro and trace elements in the surrounding environment. Statistical analysis emphasizing bees and wax correlated Cd with the Strážske area, possibly attributed to the intensified industrial activity in this region. 相似文献
66.
梅州地区几种蔬菜中硒含量的初步调查 总被引:1,自引:0,他引:1
采用原子荧光光度法测定了梅州地区种植的5种农作物生菜、西洋菜、春菜、番薯叶和茶树菇中微量元素硒的含量,为人们在饮食过程中摄入适量的硒,保障人体健康提供参考。 相似文献
67.
正向成像技术是正向计算与反演相结合的密度重建技术的基础。为了正确获取闪光照相面光源下复杂客体的正向计算数值图像,提出了面光源点源化的思想,并用窗口化的探测系统模糊、径迹法等技术得到了更加准确的、含系统模糊的正向投影矩阵以及方程。利用含系统模糊的正向投影方程计算实验客体的正向投影,获得了与实验结果一致的边界信息。含系统模糊的正向投影方程和逆问题求解的约束共轭梯度法合成了整体密度重建方法。整体密度重建方法应用于FTO客体的模拟图像和实验图像,都能够将模糊控制在1~2个像素。 相似文献
68.
69.
复眼照明系统利用复眼透镜,可实现高亮度和较好的亮度均匀性,并且有较成熟的偏振处理方法,在投影系统特别是基于偏振光的投影系统中能提供比光棒照明系统更加高的亮度和好的均匀性的画面,使得光能利用率和图像均匀性有了较大的提高。在对复眼照明系统的原理进行分析的基础上,设计了一种用于投影光机的复眼照明系统,并用Matlab对该系统进行了光线追迹的仿真程序设计。对复眼照明系统的光线追迹进行了仿真。实际应用证明,在LCoS中采用本方案设计的照明系统比光棒照明系统具有更高的亮度和更好的均匀性。 相似文献
70.
糖尿病大鼠微量元素与动脉血栓形成的关系 总被引:1,自引:0,他引:1
为研究糖尿病大鼠微量元素的含量变化及其与动脉血栓形成的关系,用链脲佐菌素(STZ)诱导出糖尿病大鼠模型,三氯化铁(FeCl3)造颈总动脉血栓后,测定血糖、胰岛素(INS)、6-酮-前列腺素F1α(6-K-PGF1α)、血栓素B2(TXB2)、内皮素(ET1)以及全血微量元素镁、锌含量。结果表明,①与正常对照组比,糖尿病大鼠的血糖、TXB2、ET1和锌的含量、ρ(TXB2)/ρ(6-K-PGF1α)、(T/P)比值及血栓质量增加(P〈0.05),INS含量降低(P〈0.001),镁和6-K-PGF1α含量无改变(P〉0.05);②糖尿病组的TXB2与糖、锌(P=0.001)、胰岛素正相关(P=0.003),ET1仅与锌正相关(P=0.096),6-K-PGF1α与镁、锌无相关关系。提示:①糖尿病大鼠血管内皮功能受损,血液处于T/P失衡的高凝状态,更易形成动脉血栓;②糖和锌代谢紊乱在T/P失衡和内皮功能损伤中有重要作用。 相似文献