Analysis of phenolic acids and flavonoids in honey

Honey is rich in phenolic acids and flavonoids, which exhibit a wide range of biological effects and act as natural antioxidants. The analysis of polyphenols has been regarded as a very promising way of studying floral and geographical origins of honeys. This review surveys recent literature on determination of these active compounds in honey. The analytical procedure to determine individual phenolic compounds involves their extraction from the sample matrix, analytical separation and quantification. We pay particular attention to sample pre-treatment and separation techniques (e.g., high-performance liquid chromatography and electrophoresis).     

微流控芯片分析化学实验室

以作者课题组近10年所开展的系统研究工作为基础, 介绍微流控芯片分析化学实验室操作单元构建及系统整体集成, 并特别关注芯片分析化学实验室在分子水平、细胞水平和模式生物水平的应用, 在科学研究层面上证明了这种置于芯片上的分析化学实验室的可行性, 显示了其在生物医学领域广阔的应用前景.     

Orthogonal array optimization of microwave-assisted derivatization for determination of trace amphetamine and methamphetamine using negative chemical ionization gas chromatography–mass spectrometry

An orthogonal array design (OAD) was applied to optimize microwave-assisted derivatization (MAD) for analysis of trace amphetamine (AM) and methamphetamine (MA) by negative chemical ionization gas chromatography–mass spectrometry (NCI GC–MS). The 2,3,4,5,6-pentafluorobenzoyl chloride (PFBC) was used as a derivatization reagent. Experimental factors including solvent, microwave power, and irradiation time at four-levels were studied in 16 trials by OAD₁₆ (4⁴). The significance of these factors was investigated using analysis of variance (ANOVA) and percent contribution (PC). Solvent is statistically demonstrated a chief factor; microwave power and irradiation time are secondary factors. Under the optimum condition, calibration curve of AM is linear over a range from 0.01 to 100 ng mL⁻¹ with correlation coefficient 0.9988, and MA from 0.1 to 1000 ng mL⁻¹ with correlation coefficient 0.9951. The limit of detection (LOD) is 1.20 pg mL⁻¹ for AM and 13.04 pg mL⁻¹ for MA. An applicability of the method was tested by analyzing urine samples from amphetamine-type stimulants (ATS)-abusing suspects. Consequently, the OAD method not only optimizes the MAD condition for determination of trace AM and MA, but identifies the effects of factor solvent, microwave power and irradiation time on the MAD performance.     

Gas chromatography–mass spectrometry screening methods for select UV filters,synthetic musks,alkylphenols, an antimicrobial agent,and an insect repellent in fish

Two screening methods have been developed for simultaneous determination of ten extensively used personal care products (PCPs) and two alkylphenol surfactants in fish. The methods consisted of extraction, clean-up, derivatization and analysis by gas chromatography–mass spectrometry with selected ion monitoring (GC–SIM–MS) or gas chromatography–tandem mass spectrometry (GC–MS/MS) techniques. Among solvents tested to assess recovery of target compounds from 1-g tissue homogenates, acetone was selected as optimal for extracting compounds with dissimilar physicochemical properties from fish tissue. Initial experiments confirmed that GC–SIM–MS could be applied for analysis of lean fillet tissue (<1% lipid) without gel-permeation chromatography (GPC), and this approach was applied to assess the presence of target analytes in fish fillets collected from a regional effluent-dominated stream in Texas, USA. Benzophenone, galaxolide, tonalide, and triclosan were detected in 11 of 11 environmental samples at concentrations ranging from; 37 to 90, 234 to 970, 26 to 97, and 17 to 31 ng/g, respectively. However, performance of this analytical approach declined appreciably with increasing lipid content of analyzed tissues. Successful analysis of samples with increased lipid content was enabled by adding GPC to the sample preparation protocol and monitoring analytes with tandem mass spectrometry. Both analytical approaches were validated using fortified fillet tissue collected from locations expected to be minimally impacted by anthropogenic influences. Average analyte recoveries ranged from 87% to 114% with RSDs <11% and from 54% to 107% with RSDs <20% for fish tissue containing <1% and 4.9% lipid, respectively. Statistically derived method detection limits (MDLs) for GC–SIM–MS and GC–MS/MS methodologies ranged from 2.4 to 16 ng/g, and 5.1 to 397 ng/g, respectively.     

偏振能量色散X射线荧光光谱法测定地质样品中18种元素

利用偏振能量色散X射线荧光光谱仪分析了硅酸盐基体样品. 选取岩石、土壤、水系沉积物等国家一级标准物质, 采用镶边粉末压片方法, 选择Al2O3偏振靶、 Mo、 Co二级靶, 在真空状态下对K、 Ca、 Ti、 Cr、 Mn、 Fe、 Ni、 Cu、 Zn、 Ga、 As、 Rb、 Sr、 Y、 Zr、 Nb、 Ba、 Pb等18种元素进行选择激发和探测, 所有元素的校正选用扩展的康普顿散射校正模型. 各元素的检出限为0.4～10.9 μg/g;除了As元素外, 均达到了1:25万多目标地球化学调查规范的要求. 根据60个地质调查多目标考核样品的分析结果, 采用Rousseau(2001)所提出的相对不确定度计算方法, 对所建立的方法进行了评估.     

金属材料分析(Ⅱ)

评述了2006～2007年两年间, 金属材料分析领域的国内现状与进展概况. 内容包括: 称量分析法;滴定分析法;分子光谱分析(分光光度法、催化动力学分光光度法);原子光谱分析(原子吸收光谱法、原子荧光光谱法、原子发射光谱法、质谱分析法、 X-射线荧光光谱法);电化学分析;金属中气体分析;原位分析;标准分析方法制定与标准物质(标准样品)研制;不确定度评定等在金属材料分析中的应用进展.参考文献420篇.     

甲醇钠引发的环氧乙烷开环聚合反应过程

运用密度泛函理论(DFT)的Dmol3方法, 计算了甲醇钠引发的环氧乙烷开环聚合的反应过程. 并运用前线轨道理论对该聚合反应的各步反应历程进行了分析. 计算结果表明, 链引发为无能垒的放热反应, 放出的能量达到92.560 kJ·mol-1, 而链增长过程则需越过100.951 kJ·mol-1的反应能垒, 链增长物种与环氧乙烷的前线轨道相对称, 可以使开环聚合反应继续进行下去. 当向反应体系中加入草酸、磷酸等质子酸时, 会立即发生链终止反应. 此外, 还对链增长过渡态的合理性进行了确认, 绘出了相应的反应势能曲线.     

Optimizing product assortment under customer-driven demand substitution

The problem of product assortment and inventory planning under customer-driven demand substitution is analyzed and a mathematical model for this problem is provided in this paper. Realistic issues in a retail context such as supplier selection, shelf space constraints, and poor quality procurement are also taken into account. The performance of three modified models, one that neglects customers’ substitution behavior, another that excludes supplier selection decision, and one that ignores shelf space limitations, are analyzed separately with computational experiments. The results of the analysis demonstrate that neglecting customer-driven substitution or excluding supplier selection or ignoring shelf space limitations may lead to significantly inefficient assortments. The effects of demand variability and substitution cost on optimal assortment and supplier selection decisions as well as on the optimal revenue are also investigated. The main contribution of this paper is the development of a practical and flexible model to aid retailers in finding optimal assortments to maximize the expected profit.     

Non-cooperative competition among revenue maximizing service providers with demand learning

This paper recognizes that in many decision environments in which revenue optimization is attempted, an actual demand curve and its parameters are generally unobservable. Herein, we describe the dynamics of demand as a continuous time differential equation based on an evolutionary game theory perspective. We then observe realized sales data to obtain estimates of parameters that govern the evolution of demand; these are refined on a discrete time scale. The resulting model takes the form of a differential variational inequality. We present an algorithm based on a gap function for the differential variational inequality and report its numerical performance for an example revenue optimization problem.     

DEA–DA for bankruptcy-based performance assessment: Misclassification analysis of Japanese construction industry

This study describes a practical use of Data Envelopment Analysis–Discriminant Analysis (DEA–DA) for bankruptcy-based performance assessment. DEA–DA is useful for classifying non-default and default firms based upon their financial performance. However, when we apply DEA–DA to a data set on corporate bankruptcy, we usually face three problems. First, there is a sample imbalance problem because the number of default firms is often limited. In contrast, we can easily obtain a large number of non-default firms. Second, there is a computational problem to deal with a large data set. We need to consider a computational strategy to reduce the dimension of a large data set. Finally, we need to consider data alignment because the location of default firms may exist within that of non-default firms. This study discusses a simultaneous occurrence of the three problems from the perspective of Japanese industrial policy on construction business. To handle the three problems, this study combines DEA–DA with principal component analysis to reduce the computational burden and then alters DEA–DA weights to address both the sample imbalance problem and the location problem. This study also discusses a combined use between DEA–DA and rank sum tests to examine statistically hypotheses related to bankruptcy assessment. As an important application, we apply the proposed approach to the Japanese construction industry and discuss why many Japanese construction firms are misclassified.