NP Separation Research Articles

Comparison of Nanoparticles and Single-Layer Centrifugation for Separation of Dead from Live Stallion Spermatozoa.

The goal of this study was to compare the efficacy of coated iron-core nanoparticles and single-layer centrifugation for separation of dead from live stallion spermatozoa. Our hypothesis was that nanoparticles would bind to dead sperm and allow for separation from live sperm using a magnet, resulting in a population of spermatozoa with a high percentage of total and progressive motility. Treatment Group 1 was an untreated control. Treatment Group 2 (nanoparticles, NP) utilized sperm incubated with nanoparticles followed by application of a magnet to remove dead sperm adhered to the coated nanoparticles. Treatment Group 3 (single-layer centrifugation, SLC) layered sperm above EquiPure™ followed by centrifugation. Semen samples were subsequently evaluated for sperm motility parameters, plasma membrane integrity, acrosome status, and morphology. The SLC technique yielded higher (p < 0.05) progressive motility (76 ± 9.2%) than the NP separation technique (59 ± 12.2%) or the untreated control (47.3 ± 5.1%). However, the total number of sperm recovered was higher (p < 0.05) in the NP technique (526.2 ± 96.6 × 106) than the SLC procedure (211.7 ± 70 × 106), yielding a higher total number of progressively motile sperm (317.6 ± 109 × 106) recovered using the NP technique than the SLC technique (157.8 ± 43.6 × 106). The percentage of live, acrosome intact sperm recovered was higher for SLC than NP. In summary, the SLC technique yielded a higher percentage of sperm motility, intact plasma membranes, and acrosome integrity, but yielded lower total sperm than with the nanoparticle separation technique.

Separation of neptunium and plutonium with neutral phosphorus ligands: A theoretical perspective

Effective treatment of the transuranic neptunium and plutonium from nuclear waste is of great importance and remains a challenge for developing advanced nuclear fuel cycles. Currently, novel ligands for efficient separation of actinides need to be designed urgently. Neutral extractants containing phosphorus have shown great potential for actinides separation. In this paper, we systematically explored the extraction and separation performances of neptunium(IV,V,VI) and plutonium(IV) by three phosphorus derivatives, di(1-methyl-heptyl) methyl phosphonate (P350), tri-iso-amyl phosphate (TiAP), and tributyl phosphate (TBP) by density functional theory (DFT). The outcomes showed that these neutral phosphorus reagents act as monodentate ligands through the PO group for all the extraction complexes. According to bonding nature analysis, the P350 ligand has the strongest complexing ability to the studied actinide cations. In addition, these ligands show a preference to coordination with Pu4+ and NpO22+ over Np4+ and NpO2+, respectively. As expected, the thermodynamic analysis demonstrated the potential application of these neutral extractants in Np and Pu separation, among which the P350 ligand is more promising than TBP and TiAP in acid solution system. This work can help to further understand the separation mechanism of Np/Pu with neutral phosphorus reagents and provide insight into the development of highly efficient extractants in recovery of Np and Pu.

Optimization of Methods for Determination of the Encapsulation Efficiency of Doxorubicin in the Nanoparticles Based on Poly(lactic-co-glycolic acid) (PLGA)

Introduction . Drug encapsulation efficiency (EE) is the important parameter of the nanoparticle-based drug formulations. Generally, the methods for evaluation of the EE are based on separation of the free and NP-bound fractions of the drug; however, applicability of these methods for a particulate formulation needs careful consideration. Aim. The purpose of the study was to optimize the procedure for evaluation of the EE for a nanoparticle-based drug formulation taking doxorubicin loaded in the PLGA nanoparticles (PLGA-Dox NP) as a model formulation. Materials and methods. The PLGA-Dox NP were prepared by a “double emulsion” method at pH of the external aqueous phase of 7.4 or 6.4. The NP size and size distribution (PDI) were determined by photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM). For the EE evaluation of doxorubicin, the NP were separated by centrifugation (CF), ultrafiltration (UF), or gel filtration. The efficiency of NP separation by the CF method was evaluated by the PLGA content in the supernatant by capillary electrophoresis (CZE). Results and discussion. The average hydrodynamic diameter of the PLGA-Dox/7.4 and PLGA-Dox/6.4 NP (FCS) was 103 ± 10 nm and 141 ± 8 nm, respectively. According to the TEM data, the main fraction of the NP averaged 50 ± 16 nm. The EE of doxorubicin, determined after the NP separation by centrifugation at 48254.g, was 78.9 ± 1.8 % for the PLGA-Dox/6.4 and 91.5 ± 0.9 % for the PLGA-Dox/7.4 NP with the residual PLGA content in the supernatant of ~5 %. At lower acceleration the NP separation was incomplete leading to underestimation of the EE. Also, the ultrafiltration method using the filters with the NMWL of 50 and 100 kDa enabled the reliable NP separation with the minimal doxorubicin adsorption on the filter (<4 %). Separation of the NP by gel filtration led to the underestimation of the EE due to considerable desorption of doxorubicin from the NP surface. Conclusion. The optimal analytical procedures for evaluation of the EE of doxorubicin in the PLGA NP are based on the NP separation by CF at 48254×g and UF using filters with NMWL of 50 and 100 kDa.

Analysis of the Possibility of Using Carbamide for Separation of U and Pu in Extractive Processing of SNF

Behavior of carbamide in HNO3 solutions on Pt and SnO2 electrodes was studied. It was found that the oxidation rate of Co(NH2)2 on the SnO2 electrode is approximately two orders of magnitude lower than that on the Pt electrode. The electrochemical reduction of U(VI) in a cell having no diaphragm on a Ti (cathode)–SbO2 (anode) pair of electrodes was examined at its concentration of 10 to 100 g/L in HNO3 solutions (0.5–2.0 M) containing carbamide (5–30 g/L). It was found that the concentration of these components affects the completeness and rate of U(IV) formation and the current efficiency. It was shown that the reduction efficiency decreases in the presence of technetium ions, and, after the current is switched off, the already formed U(IV) is oxidized to U(VI). The rate of this process grows with increasing concentration of Te and HNO3. The electrochemical behavior of carbamide on an insulated Ti cathode was examined in aqueous nitric acid solutions. It was found that, in this case, the carbamide solutions acquire on being subjected to electrolysis reducing properties toward Pu(IV) and Np(VI). A laboratory installation of mixers-settlers, assembled in accordance with the technological scheme of the first cycle of SNF processing at RT-1 plant was used to perform experiments with the use of electrochemically processed carbamide as a re-extractive agent in the procedure of Pu and Np separation from uranium. It was found that a high rate of U purification to remove Np is reached in this case, but a satisfactory mutual separation of U and Pu is not provided.

Differentiation of metallic and dielectric nanoparticles in solution by single-nanoparticle collision events at the nanoelectrode

In this work, we demonstrate a highly effective method to generate and detect single-nanoparticle (NP) collision events on a nanoelectrode in aqueous solutions. The nanoelectrode of a nanopore–nanoelectrode nanopipette is first employed to accumulate NPs in solution by dielectrophoresis (DEP). Instead of using amperometric methods, the continuous individual NP collision events on the nanoelectrode are sensitively detected by monitoring the open-circuit potential changes of the nanoelectrode. Metallic gold NPs (GNPs) and insulating polystyrene (PS) NPs with various sizes are used as the model NPs. Due to the higher conductivity and polarizability of GNPs, the collision motion of a GNP is different from that of a PS NP. The difference is distinct in the shape of the transient potential change and its first time derivative detected by the nanoelectrode. Therefore, the collision events by metallic and insulating NPs on a nanoelectrode can be differentiated based on their polarizability. DEP induced NP separation and cluster formation can also be probed in detail in the concentrated mixture of PS NPs and GNPs.

Dynamic tuning of plasmon resonance in the visible using graphene.

We report active electrical tuning of plasmon resonance of silver nanoprisms (Ag NPs) in the visible spectrum. Ag NPs are placed in close proximity to graphene which leads to additional tunable loss for the plasmon resonance. The ionic gating of graphene modifies its Fermi level from 0.2 to 1 eV, which then affects the absorption of graphene due to Pauli blocking. Plasmon resonance frequency and linewidth of Ag NPs can be reversibly shifted by 20 and 35 meV, respectively. The coupled graphene-Ag NPs system can be classically described by a damped harmonic oscillator model. Atomic layer deposition allows for controlling the graphene-Ag NP separation with atomic-level precision to optimize coupling between them.

Size determination and quantification of engineered cerium oxide nanoparticles by flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry

Facing the lack of studies on characterization and quantification of cerium oxide nanoparticles (CeO2 NPs), whose consumption and release is greatly increasing, this work proposes a method for their sizing and quantification by Flow Field-flow Fractionation (FFFF) coupled to Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Two modalities of FFFF (Asymmetric Flow- and Hollow Fiber-Flow Field Flow Fractionation, AF4 and HF5, respectively) are compared, and their advantages and limitations discussed. Experimental conditions (carrier composition, pH, ionic strength, crossflow and carrier flow rates) are studied in detail in terms of NP separation, recovery, and repeatability. Size characterization of CeO2 NPs was addressed by different approaches. In the absence of feasible size standards of CeO2 NPs, suspensions of Ag, Au, and SiO2 NPs of known size were investigated. Ag and Au NPs failed to show a comparable behavior to that of the CeO2 NPs, whereas the use of SiO2 NPs provided size estimations in agreement to those predicted by the theory. The latter approach was thus used for characterizing the size of CeO2 NPs in a commercial suspension. Results were in adequate concordance with those achieved by transmission electron microscopy, X-ray diffraction and dynamic light scattering. The quantification of CeO2 NPs in the commercial suspension by AF4-ICP-MS required the use of a CeO2 NPs standards, since the use of ionic cerium resulted in low recoveries (99±9% vs. 73±7%, respectively). A limit of detection of 0.9μgL−1 CeO2 corresponding to a number concentration of 1.8×1012L−1 for NPs of 5nm was achieved for an injection volume of 100μL.

An improved PUREX process in technetium separation by stepwise reduction

An improved PUREX process in Tc separation is introduced in this paper. Experiments including we did and done by other investigators are cited in this paper to testify the feasibility of the process. The scheme of this process is as follows: First, to extract U, Pu and most Tc, Np into the organic phase, so the concentration of Tc in the high level liquid waste (HLLW) may be very low, which can alleviate the burden of Tc treatment in HLLW vitrification. Second, in the Pu and Np separation stage to reduce or complex Pu and Np using acetohydroxamic acid, this step separates Pu and Np from the organic phase. Next, to separate Tc from U, it can be realized easily by reducing Tc to lower valance using reductant such as hydrazine or quadrivalence U. By this technology, we may resolve the problems caused by Tc remained in the HLLW such as a long time surveillance of HLLW condensate or the risk of Tc transferring into the biosphere, and meanwhile the over-consumption of reductant in the U/Pu splitting stage can be avoided.

Comprehensive two-dimensional normal-phase (adsorption)-reversed-phase liquid chromatography.

A comprehensive two-dimensional HPLC system has been developed. It is based on the use of a microbore silica column operated in normal-phase (adsorption) mode (NP) in the first dimension and a monolithic type C18 column operated in reversed-phase (RP) mode in the second dimension. The interface was a 10-port, 2-position valve equipped with two storage loops. The first column was operated at a flow rate of 20 microL/min in isocratic mode, while the monolithic column flow rate was 4 mL/min and was operated in gradient mode. The sample loops had a volume of 20 microL each, and the analysis time in the second dimension was 1 min. In this way, every fraction from the first dimension was transferred on-line to the second dimension switching the automated valve every minute. A photodiode array detector has been used after the secondary column. The use of normal- and reversed-phase mode in the two dimensions can be helpful in the separation of complex mixtures of a natural origin that contain uncharged molecules of comparable dimension, different in polarity and hydrophobicity. The use of a microbore column in the first dimension permits the injection of a small volume in the secondary column, making the transfer of incompatible solvents from the first to the second dimension possible. Since the mobile phase in the NP separation is always stronger than the mobile phase at the head of the secondary column operated in RP mode, the initial eluent strength is important in order to obtain an effective focusing of the sample. The use of a monolithic type column in the second dimension permits the performance of very fast analysis operating at higher flow rates without loss of resolution, due to a higher permeability and increased mass-transfer properties in comparison to conventional particulate columns. Due to the brief reconditioning time necessary for monolithic columns, repetitive gradients can be carried out, extending the field of application to mixtures that contain components with different polarities. The utility of the system has been demonstrated in the analysis of the oxygen heterocyclic fraction of cold-pressed lemon oil, made up of coumarins and psoralens. These components may contain hydroxyl, methoxyl, isopentenyl, isopentenyloxyl, and geranyloxyl groups and oxygen-containing modification of the terpenoid side-chain groups, such as epoxides or vicinal diol groups. The relative location of the components in the 2D plane varied in relation to their chemical structure and allowed positive peak identification. The UV spectra recorded with the photodiode array detector supplied additional information that was used for the characterization of the studied sample.

Local round robin test for determination of aromatics in diesel fuels by HPLC.

Determination of aromatics in diesel fuels by HPLC is covered by European Standard EN 12916 (April 2000). The Standard is based on former standards IP 391/90 and IP 391/95. The method used for measurements is NP HPLC and separation is performed on silica or modified silica columns with RI detection. The precision of the method was checked by determining the repeatability and reproducibility. The content of aromatics was measured in a number of commercial samples. The measurements have been performed in three different laboratories and under different working and instrumental conditions. Satisfactory agreement was established for repeatability and was slightly poorer for reproducibility. The content of polyaromatics is within the tolerance range (IP 590/99) and the content of tricyclic and higher aromatics (tri+) is close to the limit of quantitition in some samples. Clear differences in the content of polycyclic aromatics in domestic diesel and eurodiesel fuels were observed. The results have confirmed the ruggedness and robustness of the measuring method.

Reduction of Neptunium(VI) by Butyraldehyde Isomers in Nitric Acid Solution

The kinetics of the reaction between Np(VI) and butyraldehyde isomers in nitric acid solution was studied to find flow-sheet conditions of the Np separation process from U and Pu. Iso-butyraldehyde was found to have a higher reduction rate than n-butyraldehyde. The former reduction rate at T = 283 to 323 K is described by the following equation:.The latter reduction rate is described by the following equation:.

Kinetics of Reduction of Np(V) to Np(IV) by Platinum Black as Reduction Catalyst.

In order to simplify the disposal procedure of high level radioactive waste produced by spent fuel reprocessing, it is necessary to separate trans-uranium elements (TRH) from high level liquid waste (HLLW). Neptunium (Np) (V) is the dominant Np oxidation state in HLLW. Since extractability is low, its separation is extremely difficult. However, valence control of Np(V) to (IV) or (VI) allows Np separation. In a previous study on reduction kinetics of Np(V) to (IV) by hydroxylammonium in nitric acid solution, the activation energy was reported to be 105 kJ/mol(1). This value suggested that the rate of Np(V) reduction was very slow at room temperature. Although, the coexistence of platinum black with hydroxylammonium nitrate was found to give a remarkable increase in the reduction rate of Np(V) in nitric acid solution(2). In the present study, the kinetics and mechanism of the reduction reaction by platinum (Pt) black catalyst are studied, and the rate constant at room temperature is determined.

Mössbauer spectroscopy and x-ray diffraction studies of neptunium intermetallics under high pressure†

The magnetic properties of intermetallic compounds of the light actinides vary from primary local moment behaviour through itinerant electron magnetism to non-magnetic behaviour. A dominant parameter separation of the actinide ions which experimentally can be varied by the microscopic magnetic behaviour we performed Mössbauer experiments on NpAl 2, NpOs 2, NpCo 2Si 2, and NpAs using the 60 keV transition in 237Np. The magnetic hyperfine field B hf and the isomer shift S, which are a measure of the ordered magnetic moment and the s-electrondensity at the nucleus, respectively, as well as the magnetic ordering temperatures have been determined at various pressures up to 70 kbar and in the temperature range from 1.6 K to 77 K. In addition, the lattice parameter variation of NpAl 2 was measured up to 100 kbar at room temperature by X-ray diffraction. We obtained the following results: 1. In the cubic Laves phase compounds NpAl 2 and NpOs 2 with a NpNp distance at ambient pressure of 3.371 Å and 3.258 Å, respectively, we observed a strong decrease to B hf and Curie temperature with pressure indicating a progressive delocalization of the 5f electrons. This is markedly confirmed by the isomer shift. In addition , line broadenings are observed which point towards fluctuations phenomena and show that the delocalization process is of a dynamical nature [1–3]. 2. The X-ray measurements demonstrate an increase of the compressibility of NpAl 2 by a factor of 5 when a pressure of 80 kbar is applied. This behaviour further supports the picture of 5f delocalization with reduced atomic volume. A collapse of volume on account of 5f delocalization 3. has been predicted theoretically for Am metal [4], but could not yet be experimentally verified for this element. 4. In NpCo 2Si 2 which has a tetragonal structure and a nearest neighbour distance of 3.877 Å the magnetic hyperfine field remains constant under pressure. It indicates that in this compound the 5f electrons are well localized. The Néel temperature T N increases with smaller volume. The variation of T N can be explained quantitatively in terms of the rigid spin model of Ruderman-Kittel-Arrott [5, 6] 5. NpAs which has an even larger NpNp separation of 4.128 Å shows a complex hyperfine pattern at 70 kbar consisting of several subspectra. Two different lattice structures coexist: The NaCl type structure and unknown high pressure phase. The hyperfine field belonging to the former is only slightly (∼4%) reduced when pressure (70 kbar) is applied and illustrates its highly localized property. The subspectrum of the latter structure gives a reduction of B hf of ∼16% with respect to the values of the NaCl phase.