Application of the interference standard method for the determination of sulfur, manganese and iron in foods by inductively coupled plasma mass spectrometry

The interference standard method (IFS) is evaluated to improve the accuracy of the determination of S, Mn and Fe in meat and grain samples by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). Due to ICP-QMS relatively low resolution, polyatomic interferences caused by ¹⁶O₂⁺, (¹⁶OH)₂⁺, ⁴⁰Ar¹⁴NH⁺, and ⁴⁰Ar¹⁶O⁺, for example, can compromise determinations at m/z 32, 34, 55, and 56, respectively. In IFS, differently from traditional internal standard methods, plasma naturally occurring species are used to correct for variations in the interference signal rather than the analyte signal. The method is based on the hypothesis that the interfering ion and the IFS probe present similar behaviors in the plasma, and that by using the analytical (analyte plus interference)/IFS signal ratio one could reduce variations due to interference and, consequently, improve accuracy. In this work, this strategy is evaluated in real sample applications and significant improvements on accuracy are observed for ³²S, ³⁴S, ⁵⁵Mn, and ⁵⁶Fe determinations. Recoveries ranging from 72% for Mn to 105% for Fe in two different standard reference materials are obtained using the ³⁸Ar probe. These analytes are successfully determined in meat and grain samples with concentrations ranging from 4.42 μg g⁻¹ for Mn in corn to 7270 μg g⁻¹ for S in chicken liver. The method is compared with other strategies such as internal standardization and mathematical correction. No instrumental modification or introduction of foreign gases is required, which is especially attractive for routine applications.     

Reexamination of the π-bond strengths within H2C=XHn systems: a theoretical study

The accurate determination of π-bond energies, D(π), in doubly-bonded species has been an important issue in theoretical chemistry. The procedure using the divalent state stabilization energy defined by Walsh has been suggested, and the procedure seems to be conceptually reasonable and applicable to all kinds of doubly-bonded species. Therefore, the aim of this study was to examine whether the procedure could be a reliable methodology for estimating the D(π) values for a variety of H(2)C=XH(n) species. To achieve a higher accuracy, the D(π) values were estimated at QCISD(T)/6-311++G(3df,2p) level of theory combined with isogyric correction. The D(π) values estimated in this work were in excellent agreement with the extant literature values. On the other hand, in determining accurate D(π) values for doubly bonded species, especially in species with lone-pair electrons such as H(2)C=O, it has been found that consideration of highly sophisticated electron correlation effects could be important. However, sufficiently accurate D(π) values have been obtainable at QCISD(T) or CCSD(T) levels with a 6-311++G(3df,2p) basis set on geometries at relatively inferior correlated levels such as MP2 and B3LYP levels with a 6-31+G(d) basis set.     

Exploration of overloaded cation exchange chromatography for monoclonal antibody purification

Cation exchange chromatography using conventional resins, having either diffusive or perfusive flow paths, operated in bind-elute mode has been commonly employed in monoclonal antibody (MAb) purification processes. In this study, the performance of diffusive and perfusive cation exchange resins (SP-Sepharose FF (SPSFF) and Poros 50HS) and a convective cation exchange membrane (Mustang S) and monolith (SO(3) Monolith) were compared. All matrices were utilized in an isocratic state under typical binding conditions with an antibody load of up to 1000 g/L of chromatographic matrix. The dynamic binding capacity of the cation exchange resins is typically below 100 g/L resin, so they were loaded beyond the point of anticipated MAb break through. All of the matrices performed similarly in that they effectively retained host cell protein and DNA during the loading and wash steps, while antibody flowed through each matrix after its dynamic binding capacity was reached. The matrices differed, though, in that conventional diffusive and perfusive chromatographic resins (SPSFF and Poros 50HS) demonstrated a higher binding capacity for high molecular weight species (HMW) than convective flow matrices (membrane and monolith); Poros 50HS displayed the highest HMW binding capacity. Further exploration of the conventional chromatographic resins in an isocratic overloaded mode demonstrated that the impurity binding capacity was well maintained on Poros 50HS, but not on SPSFF, when the operating flow rate was as high as 36 column volumes per hour. Host cell protein and HMW removal by Poros 50HS was affected by altering the loading conductivity. A higher percentage of host cell protein removal was achieved at a low conductivity of 3 mS/cm. HMW binding capacity was optimized at 5 mS/cm. Our data from runs on Poros 50HS resin also showed that leached protein A and cell culture additive such as gentamicin were able to be removed under the isocratic overloaded condition. Lastly, a MAb purification process employing protein A affinity chromatography, isocratic overloaded cation exchange chromatography using Poros 50HS and anion exchange chromatography using QSFF in flow through mode was compared with the MAb's commercial manufacturing process, which consisted of protein A affinity chromatography, cation exchange chromatography using SPSFF in bind-elute mode and anion exchange chromatography using QSFF in flow through mode. Comparable step yield and impurity clearance were obtained by the two processes.     

Spectroscopic investigation on the sonodynamic damage to proteins in the presence of berberine in vitro

In this paper, bovine serum albumin (BSA) was selected as a target molecule, and the sonodynamic damage to proteins in the presence of berberine (BER) and its mechanism were studied by means of absorption and fluorescence spectra. The results of hyperchromic effect of absorption spectra, and quenching of intrinsic fluorescence spectra indicated that the ultrasound-induced BSA molecules damage was enhanced by BER. The damage degree of BSA molecules increased with the increase in ultrasonic irradiation time and BER concentration. The results of synchronous fluorescence and three-dimensional fluorescence spectra confirmed that the synergistic effects of ultrasound and BER induced the damage of BSA molecules. The results of oxidation-extraction photometry with several reactive oxygen species (ROS) scavengers indicated that the damage of BSA molecules could be mainly due to the generation of ROS, and ¹O₂ was the major mediator of the ultrasound-induced BSA molecules damage in the presence of BER.     

Doping mode, band structure and photocatalytic mechanism of B-N-codoped TiO2

The photocatalyst B and N codoped TiO₂ (B-N-TiO₂) was prepared via the sol-gel method by using boric acid and ammonia as B and N precursors. The doping mode, band structure and photocatalytic mechanism of B-N-TiO₂ were investigated well and elucidated in detail. B-N-TiO₂ showed the narrowed band gap and thus extended the optical absorption due to interstitial N and [NOB] species in the TiO₂ crystal lattice. The coexistence of interstitial N and [NOB] species in the TiO₂ crystal lattice and surface NO_x species allowed the more efficient utilization of visible light. Simultaneously, interstitial [NOB] and N species and surface B₂O₃ and NO_x species facilitated the separation of photo generated electrons and holes and suppress their recombination effectively. Hence, B-N-TiO₂ showed a higher photocatalytic activity than pure TiO₂, N-doped TiO₂ (N-TiO₂) and B-doped TiO₂ (B-TiO₂) under both UV and visible light irradiation.     

Dynamics of stochastic and nearly stochastic two-party competitions

We introduce a stochastic model to study the problem of time evolution and outcome of simple two-party competitions or battles on a lattice where each party randomly deploys its constituents or elements to the lattice. The elements have assigned strength levels that determine how competitive or effective they are against the opponent. In our models, the elements neutralize one another when they are at the same site with a combination of strength levels and numbers determining which one gains control of the site. The competitions last until complete dominance has been established by one side by eliminating the opponents or a draw is achieved (unless the time evolution is terminated via some ad hoc condition). A Markov chain approach is used to describe the time-dependent dynamics of such competitions. The advantage of the approach is that it allows us to develop a theoretical framework for describing competitive systems where a combination of random and correlated events decide the outcome. We use the approach here for studies of highly contentious stochastic battles and for that of a battle with correlated events along with stochastic events. We present the method, a simple illustrative example on how the method works and close by considering two non-trivial cases including one with a combination of stochasticity and correlations.     

高效WO3掺杂MCF催化剂的合成及其在环戊烯选择氧化制戊二醛反应中的应用

以钨酸钠和正硅酸乙酯为前驱体直接合成高含量WO₃掺杂介孔氧化硅泡沫(MCF)催化剂. 在773 K焙烧后显示出更高的热稳定性. 小角X射线散射, N₂-物理吸附和透射电子显微镜结果表明钨物种嵌入后, 材料仍保持MCF特征的三维织构介孔特征. 紫外拉曼和紫外可见漫反射光谱结果表明钨物种主要以孤立的或者低聚态的氧化钨形式存在, 所以在氧化钨质量分数(w)低于20%时氧化钨物种能够高度分散在载体上. 在环戊烯选择氧化制戊二醛反应中, 反应16 h 后环戊烯的转化率达到100%, 戊二醛的产率达到83.5%. 催化剂重复利用实验表明催化剂的稳定性较好, 没有钨物种的脱落. 这种优异的催化性能归结于合适的氧化钨含量和高分散的钨物种.     

The effect of covalent immobilization of sialic acid on the removal of lipopolysaccharide and reactive oxygen species for polyethylene terephthalate

Polyethylene terephthalate (PET) was aminolyzed with 1,6‐diaminohexane (DAH) and then sialic acid (NANA) was immobilized via amidation onto the surface. The surface concentration of NANA was determined by 2‐thiobarbituric acid (TBA) test. The hemocompatibility of the resulting PET fabrics was evaluated based on complete blood count (CBC), coagulating times, and protein adsorption. The ability to remove lipopolysaccharide (LPS) was also determined. In addition, the effect of contacting NANA‐immobilizing PET on the suppression of reactive oxygen species (ROS) production was measured by the chemiluminescence (CL) method. The results show that by immobilizing NANA onto PET, the adhesion of platelet (PLt) was reduced, and oxidative stress was suppressed. The level of LPS was also greatly reduced. Copyright © 2010 John Wiley & Sons, Ltd.     

Silicon-29 NMR Study of Alkaline Aqueous and Alcoholic Tri-butylmethyl Ammonium (TBMA) Silicate Solutions

Silicon-29 NMR spectroscopy was used to characterize aqueous and alcoholic alkaline solutions of tri-butylmethyl ammonium (TBMA) silicates. The effect of TBMA cation on the equilibrium of silicate oligomers in aqueous alkaline silicate solutions was investigated using ²⁹Si NMR spectra. It was found that TBMA cation has a structure directing role and directs the silicate species to form minor amounts of silicate anion in the presence of high concentration of silicon. Silicon-29 NMR spectra of TBMA silicate solutions indicate that considerable changes occurred by changing the Si/TBMA ratio. The distribution of silicate species was affected by the presence of the alcohols, specifically methanol.