高分辨ICP-MS测定电子级高纯异丙醇中杂质元素

利用高分辨电感耦合等离子体质谱测定电子级高纯异丙醇中的痕量金属杂质,用膜去溶进样系统直接进样,用标准加入法进行上机检测,无需前处理、快速,避免了在样品前处理时的污染问题。高分辨电感耦合等离子体质谱可以消除多分子离子干扰,降低检出限,提高定量准确性。方法的检出限为0.45~20.79 ng/L,加标法回收率为88.2%~102.6%。方法简单,结果可靠,适用于高纯异丙醇中痕量元素的快速测定。     

Effects of Desolvating Agent Types,Ratios, and Temperature on Size and Nanostructure of Nanoparticles from α‐Lactalbumin and Ovalbumin

In this study, we compare the preparation of ovalbumin (OVA) and α‐lactalbumin (α‐LA) nanoparticles using different desolvating agents (ethanol, acetone, and methanol) and water: desolvating agent volume ratios (1:3, 1:4, 1:5, 1:10, and 1:20). Also the effects of protein solution temperature (25, 50, and 80 ℃) on the size of nanoparticles and the stability of crosslinked nanoparticles for 30 d were studied. OVA and α‐LA were shown to be good candidates for nanoparticulation and nanoparticles in the range of 60 to 230 nm were obtained. The comparison between the 2 proteins offers guidance to optimize OVA and α‐LA nanoparticle fabrication and to efficiently obtain nanoparticles with desired characteristics. The particle sizes of OVA nanoparticles were found to be in the range of 60 to 160 nm, and the particle sizes of α‐LA were between 150 and 230 nm. The sizes varied with different desolvating agents: for OVA, ethanol, and methanol both produced nanoparticles smaller than 100 nm; for α‐LA, methanol produced the smallest nanoparticles. Water: desolvating agent ratios, in the studied range, did not show a significant effect on the particle sizes for both OVA and α‐LA nanoparticles. The size and morphology of the nanoparticles were found to change when the protein solutions were heated up to 50 and 80 ℃ and cooled down before nanoparticulation and most nanoparticles had a smaller diameter.     

Regulation of Ionic Distribution and Desolvation Activation Energy Enabled by In Situ Zinc Phosphate Protective Layer toward Highly Reversible Zinc Metal Anodes

Despite the merits of high specific capacity, low cost, and high safety, the practical application of aqueous Zn metal batteries (AZMBs) is plagued by the dendritic growth and corrosion reaction of Zn metal anodes. To solve these issues, a Zn₃(PO₄)₂·4H₂O protective layer is in-situ constructed on Zn foil (Zn@ZnPO) by a simple hydrothermal method, avoiding the traditional slurry-casting process. The insulating and conformable ZnPO layer improves the wettability of Zn@ZnPO and aqueous electrolyte via decreasing the contact angle to 11.7^o. Compared with bare Zn, the Zn@ZnPO possesses a lower desolvation activation energy of 35.25 kJ mol^-1, indicating that the ZnPO fasters the desolvation of hydrated Zn²⁺ ions and thereby ameliorates their transport dynamics. Micro-morphology and structural characterization show that there are no dendrites forming on the post-cycling Zn@ZnPO anodes, and the interfacial ZnPO layer remains almost identical before and after cycles. It can be explained that the electrochemically stable ZnPO layer acts as an ionic modulator to enable the homogeneous distribution of Zn²⁺ ions, inhibiting the growth of Zn dendrites. Benefiting from these advantages, the Zn@ZnPO based symmetric and full cells deliver highly reversible Zn plating/stripping behavior and long cycling lifespans.     

Chitosan nanoparticles for prolonged delivery of timolol maleate

Timolol maleate-loaded chitosan (CS) nanoparticles were prepared by desolvation method. Experimental variables such as molecular weight of CS and amount of crosslinking agent were varied to study their effect on drug entrapment efficiency, size and release rates of nanoparticles. Chemical stability of timolol maleate (TM) and crosslinking of CS were confirmed by Fourier transform infrared spectroscopy. Differential scanning calorimetric studies were performed on drug-loaded nanoparticles to investigate crystalline nature of the drug after entrapment. Results indicated amorphous dispersion of drug in the polymer matrix. Scanning electron microscopy revealed irregularly shaped particles. Mean particle size of nanoparticles ranged between 118 and 203 nm, while zeta potential ranged between +17 and +22 mV. Entrapment efficiency of nanoparticles ranged between 47.6 and 63.0%. In-vitro release studies were performed in phosphate buffer saline of pH 7.4. A slow release of TM up to 24 h was observed. A 3² full factorial design was employed and second-order regression models were used to study the response (% drug release at 4 h). Release data as analyzed by an empirical relationship suggested that drug release deviated from the Fickian trend.     

Driving Force of Crystallization Based on Diffusion in the Boundary and the Integration Layers

Crystal growth rates are notoriously difficult to predict and even experimental data are often inconsistent. By allowing for mass and energy diffusion through the molecular and thermal layers surrounding a growing crystal and for the heat effect of crystallization, a new model of crystal growth from solution is proposed and applied to crystallization of potassium chloride from aqueous solution. The driving force for crystal growth was calculated using the solubility at the interface temperature in contrast to the conventional one based on bulk temperature. A positive heat effect at the crystal interface as well as the resistances to the mass and energy transfer processes to and from the crystal surface can reduce the conventional driving force for crystal growth by more than 20 %.     

Porous structure and reduced sensitivity of 2,2’,4,4’,6,6’-hexanitrostilbene (HNS) prepared by different solvation and desolvation methods

ABSTRACT

The sensitivity and performance of energetic materials strongly depend on their microstructure. Different solvation and desolvation methods were applied to prepare high explosive HNS with modified porous structure. Vacuum pyrolysis and a novel anti-solvent extraction method have been applied on the desolvation of the HNS?DIO (HNS = 2,2?,4,4?,6,6?-hexanitrostilbene; DIO = 1,4-dioxane) solvate to obtain porous HNS, while in the solvation process, the porous HNS was exposed to the solvent vapor generated by low vacuum or heating to form porous HNS?DIO solvates. After the desolvation of the porous HNS?DIO solvates, HNS with modified porous structure was achieved. This porous HNS and modified porous HNS reveal a reduced impact and friction sensitivity, compared to the raw HNS. The microstructures of HNS tuned by these different supramolecular assembly and disassembly methods were described and the feature of the methods was also discussed. These results highlight a new, simple, effective and controllable crystal engineering strategy for the design and optimization of the microstructure of energetic materials.     

膜去溶进样高分辨ICP-MS测定半导体级硝酸中杂质元素

利用高分辨电感耦合等离子体质谱测定半导体级高纯硝酸中的痕量金属杂质,用膜去溶进样系统直接进样,用标准加入法进行上机检测,无需前处理,快速,避免了在样品前处理时的污染问题。高分辨电感耦合等离子体质谱可以消除多分子离子干扰,降低检出限,提高定量准确性。方法的检出限为0.69～23.73ng/L,加标回收率为88.2%～106.0%,方法简单,结果可靠,适用于高纯硝酸中痕量元素的快速测定。     

Preparation and optimization of doxorubicin-loaded albumin nanoparticles using response surface methodology

Background: The objective of this work was to optimize the preparation of doxorubicin-loaded albumin nanoparticles (Dox-A-Nps) through desolvation procedures using response surface methodology (RSM). A central composite design (CCD) for four factors at five levels was used in this study.

Method: Albumin nanoparticles were prepared through a desolvation method and were optimized in the aid of CCD. Albumin concentration, amount of doxorubicin, pH values, and percentage of glutaraldehyde were selected as independent variables, particle size, zeta potential, drug loading, encapsulation efficiency, and nanoparticles yield were chosen as response variables. RSM and multiple response optimizations utilizing a quadratic polynomial equation were used to obtain an optimal formulation.

Results: The optimal formulation for Dox-A-Nps was composed of albumin concentration of 17?mg/ml, amount of doxorubicin of 2?mg/ml, pH value is 9 and percentage of glutaraldehyde of 125% of the theoretic amount, under which the optimized conditions gave rise to the actual average value of mean particle size (151?±?0.43?nm), zeta potential (?18.8?±?0.21 mV), drug loading efficiency (21.4?±?0.70%), drug entrapment efficiency (76.9?±?0.21%) and nanoparticles yield (82.0?±?0.34%). The storage stability experiments proved that Dox-A-Nps stable in 4°C over the period of 4 months. The in vitro experiments showed a burst release at the initial stage and followed by a prolonged release of Dox from albumin nanoparticles up to 60?h.

Conclusions: This study showed that the RSM-CCD method could efficiently be applied for the modeling of nanoparticles, which laid the foundation of the further research of immuno nanoparticles.     

Chitosan Nanoparticles for Prolonged Delivery of Timolol Maleate

Timolol maleate-loaded chitosan (CS) nanoparticles were prepared by desolvation method. Experimental variables such as molecular weight of CS and amount of crosslinking agent were varied to study their effect on drug entrapment efficiency, size and release rates of nanoparticles. Chemical stability of timolol maleate (TM) and crosslinking of CS were confirmed by Fourier transform infrared spectroscopy. Differential scanning calorimetric studies were performed on drug-loaded nanoparticles to investigate crystalline nature of the drug after entrapment. Results indicated amorphous dispersion of drug in the polymer matrix. Scanning electron microscopy revealed irregularly shaped particles. Mean particle size of nanoparticles ranged between 118 and 203 nm, while zeta potential ranged between +17 and +22 mV. Entrapment efficiency of nanoparticles ranged between 47.6 and 63.0%. In-vitro release studies were performed in phosphate buffer saline of pH 7.4. A slow release of TM up to 24 h was observed. A 3² full factorial design was employed and second-order regression models were used to study the response (% drug release at 4 h). Release data as analyzed by an empirical relationship suggested that drug release deviated from the Fickian trend.     

Early structural evolution of native cytochrome c after solvent removal

Electrospray ionization transfers thermally labile biomolecules, such as proteins, from solution into the gas phase, where they can be studied by mass spectrometry. Covalent bonds are generally preserved during and after the phase transition, but it is less clear to what extent noncovalent interactions are affected by the new gaseous environment. Here, we present atomic-level computational data on the structural rearrangement of native cytochrome c immediately after solvent removal. The first structural changes after desolvation occur surprisingly early, on a timescale of picoseconds. For the time segment of up to 4.2 ns investigated here, we observed no significant breaking of native noncovalent bonds; instead, we found formation of new noncovalent bonds. This generally involves charged residues on the protein surface, resulting in transiently stabilized intermediate structures with a global fold that is essentially the same as that in solution. Comparison with data from native electron capture dissociation experiments corroborates both its mechanistic postulations and our computational predictions, and suggests that global structural changes take place on a millisecond timescale not covered by our simulations.