统计模拟分光光度法测定复方消咳新片组分含量

用统计模拟分光光度法测定复方消咳新片４个组分含量。按均匀设计表制备合成样品，绘制溶液的ＵＶ－ＶＩＳ吸收曲线，获得有限但足够的实验数据，用逐步回归法构造反映该复方制剂组分在灵敏波长的吸光度－组分含量经验关系的“最优”数学模型，用改进单纯形法寻优，求出未知样品的各组分含量。磺胺甲基异恶唑、甲氧苄胺嘧啶、盐酸溴已新、枸橼酸维静宁的回收率分别为１００３％、１００４％、９９９％、９９０％，标准差分别为０９１％、１４％、１２％、３９％。     

Patterns in the precision of quantitative data from multicomponent gas chromatographic or gas chromatographic-mass spectrometric analysis

The dispersion of the quantitative results in the analysis of volatile compounds from multicomponent mixtures by different fractionation techniques (solid-phase microextraction and direct thermal desorption) followed by GC or GC-MS presents nonrandom patterns related to the existence of different factors in the fractionation process or in the chromatographic separation which affect, to a different extent, the recovery of the sample components. Statistical techniques have been used to show the relative importance of these factors. The improvement in data precision achieved by using volatile compound concentration ratios is discussed.     

To what extent can an uncertainty calculation be general?

 It is argued that results of uncertainty calculations in chemical analysis should be taken into consideration with some caution owing to their limited generality. The issue of the uncertainty in uncertainty estimation is discussed in two aspects. The first is due to the differences between procedure-oriented and result-oriented uncertainty assessments, and the second is due to the differences between the theoretical calculation of uncertainty and its quantication using the validation (experimental) data. It is shown that the uncertainty calculation for instrumental analytical methods using a regression calibration curve is result-oriented and meaningful only until the next calibration. A scheme for evaluation of the uncertainty in uncertainty calculation by statistical analysis of experimental data is given and illustrated with examples from the author's practice. Some recommendations for the design of corresponding experiments are formulated.     

Development of a fluorescence model for the determination of constants associated with binding,quenching, and Förster resonance energy transfer efficiency

Determining accurate dissociation constants for equilibrium processes involving a fluorescent mechanism can prove to be quite challenging. Typically, titration curves and nonlinear least squares fitting of the data using computer programs are employed to obtain such constants. However, these approaches only consider the total fluorescence signal and often ignore other energy transfer processes within the system. The current model considers the impact on fluorescence from equilibrium binding (viz., metal-ligand, ligand-substrate, etc.), quenching, and resonance energy transfer. This model should provide more accurate binding constant as well as insights into other photonic processes. The equations developed for this model are discussed and are applied to experimental data from titrimetric experiments. Since the experimental data are generally in excess of the number of parameters that are needed to define the system, fitting is operated in an overdetermined mode and employs error minimization (either absolute or relative) to define goodness of fit. Examples of how changes in certain parameters affect the shape of the titrimetric curve are also presented. The current model does not consider chelation-enhanced fluorescence.     

Decolorization and mineralization of yellow 5 (E102) by UV/Fe2+/H2O2 process. Optimization of the operational conditions by response surface methodology

In this study, the optimization and implementation of a homogeneous photo-Fenton process for the decolorization and mineralization of a wastewater containing highly concentrated yellow 5 (E102) dye, resulting from an industry placed in the suburbs of Medellin (Colombia), is presented. Response surface methodology was applied as a tool for the optimization of operational conditions such as initial dyestuff concentration, H₂O₂ concentration, and UV-radiation power (number of lamps). The decolorization, degradation and mineralization efficiencies were used as response variables. The following conditions were found to be optimal for decolorization and mineralization of yellow 5: UV radiation of 365 nm (4 W, one lamp), dye concentration of 200 mg/L, Fe²⁺ concentration of 1.0 mM, H₂O₂ concentration of 1.75 mL/L, treatment time of 180 min, Fe²⁺ concentration of 1 mM and pH = 3. Under these conditions (180 min), the photo-Fenton process allowed us to reach ca. 100% of color dye degradation, 99% of COD degradation, and 85% of mineralization (TOC). The scavenging effect of the Cl^– anion on the photodegradation process was also confirmed.     

Experimental and theoretical study of thermodynamic properties of levoglucosan

The heat capacity of levoglucosan was measured over the temperature range (5 to 370) K by adiabatic calorimetry. The temperatures and enthalpies of a solid-phase transition and fusion for the compound were found by DSC. The obtained results allowed us to calculate thermodynamic properties of crystalline levoglucosan in the temperature range (0 to 384) K. The enthalpy of sublimation for the low-temperature crystal phase was found from the temperature-dependent saturated vapor pressures determined by the Knudsen effusion method. The thermodynamic properties of gaseous levoglucosan were calculated by methods of statistical thermodynamics using the molecular parameters from quantum chemical calculations. The enthalpy of formation of the crystalline compound was found from the experiments in a combustion calorimeter. The gas-phase enthalpy of formation was also obtained at the G4 level of theory. The thermodynamic analysis of equilibria of levoglucosan formation from cellulose, starch, and glucose was conducted.     

Lichens biomonitoring as feasible methodology to assess air pollution in natural ecosystems: Combined study of quantitative PAHs analyses and lichen biodiversity in the Pyrenees Mountains

The air quality in the Aragón valley, in the central Pyrenees, has been assessed by evaluation of lichen biodiversity and mapped by elaboration of the Index of Air Purity (IAP) based on observations of the presence and abundance of eight kinds of lichen with different sensitivity to air pollution. The IAP values obtained have been compared with quantitative analytical measures of 16 PAHs in the lichen Evernia prunastri, because this species was associated with a wide range of traffic exposure and levels of urbanization. Analyses of PAHs were carried out by the DSASE method followed by an SPE clean-up step and GC–MS analysis. The concentration of total PAHs found in lichen samples from the Aragón valley ranged from 692 to 6420 ng g⁻¹ and the PAHs profile showed predominance of compounds with three aromatic rings. The influence of the road traffic in the area has been shown because values over the median concentration of PAHs (>1092 ng g⁻¹), percentage of combustion PAHs (>50%), and equivalent toxicity (>169) were found in lichens collected at places exposed to the influence of traffic. The combination of both methods suggests IAP as a general method for evaluating the air pollution referenced to PAHs because it can be correlated with the content of combustion PAHs and poor lichen biodiversity can be partly explained by the air pollution caused by specific PAHs. Figure Map of the air pollution level in the Aragón valley (Pyrenees) based on the Index of Air Purity (IAP) calculation (lichen biodiversity)     

选矿产品矿物自动分析的光片制备

基于扫描电子显微镜的矿物自动分析仪(Quantitative Evaluation of Minerals by Scanning Electronic Microscopy)、MLA(Mineral Liberation Analyser)和AMICS(Advanced Mineral Identification and Characterization System)可用于测定选矿产品中目的矿物的粒度和单体解离度,为确定合理的磨矿细度以及优化选矿工艺流程提供依据。环氧树脂光片的制备是矿物自动识别和测量的最关键的一环,其代表性直接关系到后续数据测量的准确性和真实性。对于金属矿产品来说,由于选矿产品中矿物颗粒粗细不均、密度差异较大,在环氧树脂胶结固化过程中矿物颗粒会产生明显的分异作用并互相黏连,造成分析结果失真。实验证明,把样品与晶质石墨混均,然后加入环氧树脂以及固化剂搅拌混合倒入圆柱状模具进行冷镶嵌,待样品固化后再沿圆柱体的纵向进行切割,并对其切割面进行粗磨、细磨、精磨以及抛光,就可以制备出样品分散性好、分布均匀、表面光滑平整的具有代表性的环氧树脂光片。     

青藏高原雪冰样品中低含量水溶金属离子分析方法对比研究

从采自青藏高原阿汝和古里雅冰川的两支冰芯中选取31个样品,分别用三种仪器对比分析K^+、Na^+、Ca^2+、Mg^2+四种水溶金属离子,寻求最佳分析方案。分析结果对比发现,电感耦合等离子体发射光谱(ICP-OES)法在K+测量中存在困难,而离子色谱(IC)法和电感耦合等离子体质谱(ICP-MS)法均能够满足要求,且分析结果具有高度的一致性,四种离子的相关系数(R2)均在0.97以上,且并未出现ICP-MS法比IC法测量值明显偏高的现象。因此,除IC法外,ICP-MS法也是检测青藏高原雪冰样品中水溶金属离子的有效手段,其测定速度更快,且可以同时进行微、痕量元素检测,适用于大批量冰芯样品的快速分析。     

Membrane lipids are both the substrates and a mechanistically responsive environment of TMEM16 scramblase proteins

Recent discoveries about functional mechanisms of proteins in the TMEM16 family of phospholipid scramblases have illuminated the dual role of the membrane as both the substrate and a mechanistically responsive environment in the wide range of physiological processes and genetic disorders in which they are implicated. This is highlighted in the review of recent findings from our collaborative investigations of molecular mechanisms of TMEM16 scramblases that emerged from iterative functional, structural, and computational experimentation. In the context of this review, we present new MD simulations and trajectory analyses motivated by the fact that new structural information about the TMEM16 scramblases is emerging from cryo-EM determinations in lipid nanodiscs. Because the functional environment of these proteins in in vivo and in in vitro is closer to flat membranes, we studied comparatively the responses of the membrane to the TMEM16 proteins in flat membranes and nanodiscs. We find that bilayer shapes in the nanodiscs are very different from those observed in the flat membrane systems, but the function-related slanting of the membrane observed at the nhTMEM16 boundary with the protein is similar in the nanodiscs and in the flat bilayers. This changes, however, in the bilayer composed of longer-tail lipids, which is thicker near the phospholipid translocation pathway, which may reflect an enhanced tendency of the long tails to penetrate the pathway and create, as shown previously, a nonconductive environment. These findings support the correspondence between the mechanistic involvement of the lipid environment in the flat membranes, and the nanodiscs. © 2019 Wiley Periodicals, Inc.