Validation and use of three complementary analytical methods (LC–FLS, LC–MS/MS and ICP–MS) to evaluate the pharmacokinetics, biodistribution and stability of motexafin gadolinium in plasma and tissues

Liquid chromatography–fluorescence (LC–FLS), liquid chromatography–tandem mass spectrometry (LC–MS/MS) and inductively coupled plasma–mass spectrometry (ICP-MS) methods were developed and validated for the evaluation of motexafin gadolinium (MGd, Xcytrin) pharmacokinetics and biodistribution in plasma and tissues. The LC–FLS method exhibited the greatest sensitivity (0.0057 μg mL⁻¹), and was used for pharmacokinetic, biodistribution, and protein binding studies with small sample sizes or low MGd concentrations. The LC–MS/MS method, which exhibited a short run time and excellent selectivity, was used for routine clinical plasma sample analysis. The ICP–MS method, which measured total Gd, was used in conjunction with LC methods to assess MGd stability in plasma. All three methods were validated using human plasma. The LC–FLS method was also validated using plasma, liver and kidneys from mice and rats. All three methods were shown to be accurate, precise and robust for each matrix validated. For three mice, the mean (standard deviation) concentration of MGd in plasma/tissues taken 5 hr after dosing with 23 mg kg⁻¹ MGd was determined by LC–FLS as follows: plasma (0.025±0.002 μg mL⁻¹), liver (2.89±0.45 μg g⁻¹), and kidney (6.09±1.05 μg g⁻¹). Plasma samples from a subset of patients with brain metastases from extracranial tumors were analyzed using both LC–MS/MS and ICP–MS methods. For a representative patient, ≥90% of the total Gd in plasma was accounted for as MGd over the first hour post dosing. By 24 hr post dosing, 63% of total Gd was accounted for as MGd, indicating some metabolism of MGd.     

Effect of growth temperature on the ZnO nanowires prepared by thermal heating of Zn powders

ZnO nanowires have been synthesized by heating Zn powders under nitrogen (N₂) gas atmosphere. The influence of the growth temperature on the morphology, structure, and photoluminescence (PL) properties of ZnO nanowires has been investigated. At the higher-temperature growth process, thinner nanowires have been obtained. Interestingly, it is observed that the variation of growth temperature has significantly affected the photoluminescence spectra of the ZnO nanowires, showing an enhancement in the relative intensity of the green to UV emission bands with the increase of the growth temperature. In addition, the oxygen sensing properties of the as-synthesized ZnO nanowires were tested.     

Temperature-controlled growth and photoluminescence of AlN nanowires

By varying the substrate temperature in the range of 800-1000 °C, the conditions for the synthesis of AlN nanowires were optimized. Al powders were heated under flowing ammonia gas. The samples were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and photoluminescence (PL) spectroscopy. Based on the absence of tip particles, the growth mechanism of AlN nanowires was considered to follow a vapor-solid process. The overall intensity of the PL spectra was increased by increasing the synthesis temperature, whereas their shapes were changed by varying the synthesis temperature. The associated emission mechanisms are discussed.     

Molecular dynamics simulation of solvent-polymer interdiffusion: Fickian diffusion

The interdiffusion of a solvent into a polymer melt has been studied using large scale molecular dynamics and Monte Carlo simulation techniques. The solvent concentration profile and weight gain by the polymer have been measured as a function of time. The weight gain is found to scale as t(1/2), which is expected for Fickian diffusion. The concentration profiles are fit very well assuming Fick's second law with a constant diffusivity. The diffusivity found from fitting Fick's second law is found to be independent of time and equal to the self-diffusion constant in the dilute solvent limit. We separately calculated the diffusivity as a function of concentration using the Darken equation and found that the diffusivity is essentially constant for the concentration range relevant for interdiffusion.     

Hydrogen absorption in LaNi4.9Fe0.1

The magnetic properties of LaNi_4.9Fe_0.1 and its hydride have been studied by making Mössbauer and magnetic susceptibility measurements. ⁵⁷Fe Mössbauer spectroscopy shows a small increase in the isomer shift after hydriding. An increase in the magnetic susceptibility after hydriding was observed.     

封装Fe(Ⅲ),Ni(Ⅱ)和Cu(Ⅱ)的N,N'-双邻羟苯亚甲基-1,2-苯二胺络合物的Y分子筛催化4-氯-3-甲基苯酚氧化反应

将Fe(Ⅲ),Ni(Ⅲ)和Cu(Ⅱ)与N,N'-双邻羟苯亚甲基-1,2-苯二胺配位的络合物封装在Y分子筛内,作为多相类Fenton的高级氧化过程的催化剂,用于降解4-氯-3-甲基苯酚(PCMC).采用粉末X射线衍射、热重、N2吸附-脱附、红外光谱、元素分析和扫描电镜对所制催化剂的物化性质进行了表征,并考察了H2O2的初始浓度、催化剂用量、温度和pH值等因素对模型有机污染物降解的影响.结果表明,在Fe(Ⅲ),Ni(Ⅲ)和Cu(Ⅱ)催化剂作用下,在较低的酸性pH值、催化剂用量0.1 g、H2O2的初始浓度0.35 mmol/L的条件下,于50℃反应120 min几乎可以完全去除PCMC.同时还考察了所制PCMC降解催化剂的重复使用性能,提出了可能的催化剂失活机理,也研究了PCMC氧化过程中可能的中间产物和动力学.     

Rheological characteristics of municipal thickened excess activated sludge (TEAS): impacts of pH,temperature, solid concentration and polymer dose

Rheological characterization of sludge is known to be an essential tool to optimize flow, mixing and other process parameters in wastewater treatment plants. This study deals with the characterization of thickened excess activated sludge in comparison to raw primary sludge and excess activated sludge. The effects of key parameters (total solid concentration, temperature, and pH) on the rheology and flow behavior of thickened excess activated sludge were studied. The rheological investigations were carried out for total solid concentration range of 0.9–3.7 %w/w, temperature range of 23–55 °C, and pH range of 3.6–10.0. Different rheological model equations were fitted to the experimental data. The model equations with better fitting were used to calculate the yield stress, apparent, zero-rate, infinite-rate viscosities, flow consistency index, and flow index. The decrease in concentration from 3.7 to 3.1 %w/w resulted in a drastic reduction of yield stress from 27.6 to 11.0 Pa, while a further reduction of yield stress to 1.3 Pa was observed as solid concentration was reduced to 1.3 %w/w. The viscosity at higher shear rate (>600 s^?1) decreased from 0.05 Pa·s down to 0.008 Pa·s when the total solid concentration was reduced from 3.7 to 0.9 %. Yield stress decreased from 20.1 Pa down to 8.3 Pa for the Bingham plastic model when the temperature was raised from 25 to 55 °C. Activation energy and viscosity also showed decreasing trends with increasing temperature. Yield stress of thickened excess activated sludge increased from a value of 6.0 Pa to 8.3 Pa when the pH was increased from 3.6 to 10.0. The effect of polymer dose on the rheological behavior of the thickening of excess activated sludge was also investigated, and the optimum polymer dosage for enhanced thickener performance was determined to be 1.3 kg/ton DS.     

Photochemistry of 4‐ and 5‐ phenyl substituted isoxazoles

5‐Phenylisoxazole ( 4 ) and 4‐phenylisoxazole ( 22 ) underwent phototransposition to 5‐phenyloxazole ( 5 ) and 4‐phenyloxazole ( 24 ) respectively. Labeling with deuterium or methyl confirmed that these phototranspositions occurred via the P₄ pathway which involves only interchange of the N2 and C3 ring position. Thus, 4‐deuterio‐5‐phenylisoxazole ( 4‐4d ), 4‐methyl‐5‐phenylisoxazole ( 10 ), and 5‐methyl‐4‐phenylisoxazole ( 23 ) phototransposed to 4‐deuterio‐5‐phenyloxazole ( 5‐4d ), 4‐methyl‐5‐phenyloxazole ( 11 ), and 5‐methyl‐4‐phenyloxazole ( 25 ) respectively. In addition to phototransposition, isoxazoles 4, 10 , and 23 also underwent photo‐ring cleavage to yield benzoylacetonitrile (9), α‐benzoylpropionitrile ( 15 ), and aceto‐α‐phenylacetonitrile ( 26 ) respectively. Irradiation of 5‐phenyl‐3‐(trifluoromethyl)isoxazole ( 16 ) in acetonitrile led to 5‐phenyl‐2‐(trifluoromethyl)oxazole ( 17 ), the P₄ phototransposition product. Irradiation of 16 in methanol led to a substantial decrease in the yield of 17 and to the formation of a mixture of (E) and (Z)‐2‐methoxy‐2‐(trifluoromethyl)‐3‐benzoylaziridines 18a and 18b .     

Beyond potentiometry: robust electrochemical ion sensor concepts in view of remote chemical sensing

For about 100 years, potentiometry with ion-selective electrodes has been one of the dominating electroanalytical techniques. While great advances in terms of selective chemistries and materials have been achieved in recent years, the basic manner in which ion-selective membranes are used has not fundamentally changed. The potential readings are directly co-dependent on the potential at the reference electrode, which requires maintenance and for which very few accepted alternatives have been proposed. Fouling or clogging of the exposed electrode surfaces will lead to changes in the observed potential. At the same time, the Nernst equation predicts quite small potential changes, on the order of millivolts for concentration changes on the order of a factor two, making frequent recalibration, accurate temperature control and electrode maintenance key requirements of routine analytical measurements. While the relatively advanced selective materials developed for ion-selective sensors would be highly attractive for low power remote sensing application, one should consider solutions beyond classical potentiometry to make this technology practically feasible. This paper evaluates some recent examples that may be attractive solutions to the stated problems that face potentiometric measurements. These include high-amplitude sensing approaches, with sensitivities that are an order of magnitude larger than predicted by the Nernst equation; backside calibration potentiometry, where knowledge of the magnitude of the potential is irrelevant and the system is evaluated from the backside of the membrane; controlled current coulometry with ion-selective membranes, an attractive technique for calibration-free reagent delivery without the need for standards or volumetry; localized electrochemical titrations at ion-selective membranes, making it possible to design sensors that directly monitor parameters such as total acidity for which volumetric techniques were traditionally used; and controlled potential coulometry, where all ions of interest are selectively transferred into the ion-selective organic phase, forming a calibration-free technique that would be exquisitely suitable for remote sensing applications.