The use of boric acid as a modifier for the determination of trace amount of indium in high purity antimony by electrothermal atomic absorption is described. It was found that the negative influence of the hydrofluoric acid, used for the digestion could not be eliminated by using stabilized temperature platform furnace (STPF) alone. Due to the high dissociation energy (D0 = 506 kJ mol−1) of indium fluoride, it is difficult to dissociate in the gas phase and hence is lost. In presence of HF (used for the dissolution of antimony), the universal Pd-Mg modifier does not work satisfactorily. Additionally, rising corrosion and reduced tube lifetime were observed when the acid digested (HF-HNO3) antimony solution was injected in to the platform. Improvement in platform life and elimination of interferences were achieved by the addition of boric acid as a chemical modifier together with ruthenium coating of the platform. Corrosive changes of the transversely heated graphite atomizer (THGA) platform surface were examined by scanning electron microscopy. The standard addition method was applied. A characteristic mass of 36 pg was obtained. The detection limit of the proposed method is around 0.04 μg g−1. The developed method was applied to the determination of indium in real samples. The data obtained by this method were in good agreement with those obtained by ICP-MS. 相似文献
The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions.
The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential
and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated
sheath are made. 相似文献
The hepatitis B surface antigen manufactured by recombinant DNA technology is extracted from the culture media by density gradient centrifugation using cesium salts. Cesium is considered to be toxic, because it affects active ion transport by blocking potassium channels. The residual trace levels of cesium in hepatitis B vaccine samples are determined by suppressed ion chromatography. Hepatitis B vaccines contain various buffer salts, aluminum-containing adjuvants, proteins and traces of iron. The polyvalent cations (Al3+, Fe3+) and proteins degrade the chromatographic performance in terms of decreased retention time and poor reproducibility. Different sample preparation approaches were evaluated with the aim of eliminating these foulants: (1) filtration, (2) digestion and (3) digestion-protein precipitation. Quantitative elimination of these foulants was achieved in the digestion-protein precipitation sample clean-up approach. Cesium was separated on the IonPac CS17 column with suppressed conductivity detection. The results of the ion chromatography (IC) method were compared with ICP-MS analysis. The precision of determination was better than 6.5% (relative standard deviation) with a method detection limit of 45 ng mL−1. The expanded uncertainty in the measurement at 95% confidence level (coverage factor 2) is better than 16.3%.
The hot rotating compound systems formed in heavy ion collisions are studied using the statistical theory with a view to determine
the spin and temperature dependence of nuclear shapes. Shape transitions are observed for these systems at particular spin
values. The neutron and proton separation energies for heavier high spin systems have been evaluated. Results are presented
for
70170
Yb and
78194
Pt. 相似文献
Summary A sensitive procedure for the determination of cobalt in high-purity aluminium using DPCSV through adsorptive accumulation of Co(DMG)2 on HMDE in triethanolamine + NH4OH buffer is described. Analysis of NBS SRM C-1257 and a reactor grade aluminium sample is reported. Prior to the determination, cobalt was separated from Al and Ni on AG-1 X8 resin in 9 mol/l HCl. The results have been cross-validated by INAA. 相似文献
A neutron activation analysis procedure has been developed for the indirect determination of phosphorus as orthophosphate at ppb levels, via the formation of antimonyl phosphomolybdic acid. The complex is adsorbed on Sephadex G-25 resin and the antimony is estimated through NAA, allowing the determination of phosphorus. The procedure provides an easy method to adopt for the routine determination of phosphorus at 10 ng ml–1 levels with good precision, in water samples. 相似文献
40 MeV -particles have been used to determine oxygen impurity at ppm levels in silicon, copper, and stainless steel, through the radiochemical separation of18F from the matrix. The separation of18F has been carried out by two techniques, viz.(1) distillation of H2SiF6 and (2) precipitation of KBF4 and some modification has been applied in the separation, depending on the nature of interferences from the matrix. Instrumental approach was also carried out to determine the oxygen impurity at 100 ppm in Si matrix because this approach is not possible in Cu and stainless steel samples due to matrix activity. 相似文献
Elucidating single-atom effects on the fundamental properties of nanoparticles is challenging because single-atom modifications are typically accompanied by appreciable changes to the overall particle's structure. Herein, we report the synthesis of a [Cu58H20PET36(PPh3)4]2+ ( Cu58 ; PET: phenylethanethiolate; PPh3: triphenylphosphine) nanocluster—an atomically precise nanoparticle—that can be transformed into the surface-defective analog [Cu57H20PET36(PPh3)4]+ ( Cu57 ). Both nanoclusters are virtually identical, with five concentric metal shells, save for one missing surface copper atom in Cu57 . Remarkably, the loss of this single surface atom drastically alters the reactivity of the nanocluster. In contrast to Cu58 , Cu57 shows promising activity for click chemistry, particularly photoinduced [3+2] azide-alkyne cycloaddition (AAC), which is attributed to the active catalytic site in Cu57 after the removal of one surface copper atom. Our study not only presents a unique system for uncovering the effect of a single-surface atom modification on nanoparticle properties but also showcases single-atom surface modification as a powerful means for designing nanoparticle catalysts. 相似文献