多波长K系数分光光度法的应用研究

同时测定混合物中相互干扰的各组分含量,在很多领域具有实际意义。本文以食品中柠檬黄、日落黄、胭脂红测定为例,讨论了多波长K系数法在混合体系中的应用,效果良好。与多波长线性回归法相比,该方法准确度高,精密度也较好。     

光度法对不同水期黄河甘宁蒙段表层沉积物中磷积累程度和交换能力的比较研究

磷是水体富营养化的主要控制因素,在外源磷输入逐步得到控制后,作为内源磷主要来源的表层沉积物对黄河水体水质的影响作用不容忽视。掌握表层沉积物中磷的积累程度以及沉积物-水界面磷的交换能力,对区域内水环境的治理和磷负荷的调控具有重要的意义。选择黄河甘宁蒙段作为研究区域,分别采集丰水期(2011.07)、枯水期(2014.05)和平水期(2014.10)表层沉积物样品,使用标准测试程序(SMT)和钼锑抗分光光度法测定样品中磷赋存形态,并在实验条件下模拟表层沉积物对磷的等温吸附及吸附动力学过程。研究发现：(1) 相比于国内主要河流表层沉积物中磷的形态特征,黄河甘宁蒙段表层沉积物中有机磷(OP)和铁/铝结合态磷(NaOH-P)含量相对较低,钙结合态磷(HCl-P)含量较高;各形态磷含量的平均值均在丰水期最高,表明丰水期表层沉积物中磷的积累程度最高,黄河甘宁蒙段水环境受到沿程农业发展的冲击较大。因此,合理使用含磷化肥和优化灌渠退水水质是未来降低黄河水体磷污染风险的发展方向。(2) 基于低磷浓度下等温吸附中各采样点表层沉积物吸附-解吸平衡浓度(EPC₀)与判断水体发生富营养化的磷浓度阈值的比较发现,研究区域所有水期大多数采样点表层沉积物发挥着“磷源”的作用,存在向上覆水释放磷的趋势,且枯水期中多数采样点的EPC₀值较高,“磷源”作用更加明显;基于L模型和F模型对高磷浓度下等温吸附的拟合参数,显示丰水期表层沉积物对磷的持留能力最强,枯水期次之,平水期最小,所有采样点表层沉积物对磷的吸附过程均易发生;基于吸附动力学曲线的变化趋势可知,所选择的各采样点磷吸附量在反应开始的12 h内迅速增大,12~48 h内吸附量逐渐增加并趋于稳定;基于伪二级动力学方程对吸附动力学过程的拟合结果,表明表层沉积物对磷吸附过程的反应速率受化学吸附控制为主;从同一水期不同采样点吸附过程中的限速步骤不同及不同水期邻近采样点吸附过程中限速步骤均为微孔扩散的结果发现,表层沉积物组成和理化性质的差异对磷吸附速率的影响大于不同水期条件下上覆水流速和流量的变化。     

电感耦合等离子体质谱法研究黄河甘宁蒙段附近居民砷暴露水平

人类砷暴露可以通过空气、饮用水和食物等途径.运用ICP-MS方法分析了四个采样点河曲(Hequ,HQ)、石嘴山(Shizuishan,SZS)、中卫(Zhongwei,ZW)和临夏(Linxia,LX)的69份当地居民发样及四个黄河过滤水样的总砷含量,探究了头发中砷水平在不同性别及年龄中的差异,并对发样中砷与水样中砷的相关性进行了分析.人发样品采用微波消解方法进行前处理,消解效果良好.结果表明,该方法准确度及精密度良好,回收率为90.1%~101.9%,RSD值为2.9%~4.2%.结果显示,该研究地区居民发样砷含量范围为0.01~1.73 μg·g-1,平均值为0.33 μg·g-1,不同采样点的砷含量顺序为ZW>HQ>LX>SZS.Kruskal Wallis检验显示该文中不同采样点发样砷含量存在显著性差异(p=0.010),说明研究地区的生活区域对居民发样砷含量具有影响,而不同性别(p=0.158)和不同年龄(p=0.159)组居民发样砷含量无明显差异,但男性发砷平均值含量高于女性,不同年龄组间呈现发样砷含量随年龄增大而下降的趋势.与文献相比,该研究发样砷含量较高于多数地区而明显低于地方性砷中毒区域.黄河水样中砷含量范围为2.31~10.41 μg·L-1.与黄河下游等地区相比砷含量较高,但未超出地表水环境Ⅲ类标准.Pearson相关性系数表明,水中砷元素与铅、铜、铬、镉等元素均具有相关性,与人发砷含量具有显著正相关.总之,采样点附近居民具有较高砷暴露风险,且该风险可能来自于工农业排放.研究结果为甘宁蒙等西北民族地区重金属污染研究提供实验数据和理论依据.     

基于三维荧光光谱结合平行因子分析对春季北黄海有色溶解有机物的研究

利用三维荧光光谱(EEMs)结合平行因子分析(PARAFAC),对我国春季北黄海海水样品的荧光光谱进行了研究和分析。结果表明,北黄海有色溶解有机物(CDOM)中的荧光溶解有机物(FDOM)可分为四个组分,其中两组为类腐殖荧光组分c1(260,315/425)和c2(295,355/490),两组为类蛋白荧光组分c3(275/310)和c4(230,290/345)。四个组分之间不同程度的线性相关性说明了它们同源相似性,类腐殖质两组分之间的相关性最高,类蛋白质两组分次之。四个荧光组分和总荧光强度在平面分布和垂直分布都呈现近岸高,远岸低的趋势,同时除去陆源输入影响,海洋自身的水团运动和生物活动也影响着北黄海CDOM的分布。聚类分析进一步说明了北黄海不同区域的总荧光强度分布特征,也体现了整体上CDOM的均一性。荧光指数FI、腐殖化指数HIX和生源指数BIX在一定程度上指示了北黄海CDOM的来源,说明近岸区域陆源的影响较大,而向海一侧则受生物活动的作用影响较大,此结论与前述荧光组分的分布规律吻合。     

物理人眼中的《千里江山图》--探索物理教学的跨学科融合

故宫博物院馆藏的北宋名画《千里江山图》通过央视《国家宝藏》栏目为普通观众所熟知.该画作被视为青绿山水画中的巨制杰构,虽历经近千年依然璀璨如初,秘密就在于其颜料全部由宝石矿物制成.本文根据物理化学原理将这些颜料的呈色机理一一揭示.这种跨界思考不仅能激发学生的学习兴趣,更能实现现代科技教育与传统文化的完美融合.     

Efficient synthesis of analogs of safflower yellow B, carthamin, and its precursor: two yellow and one red dimeric pigments in safflower petals

The synthesis of analogs (8, 12, 14) of two yellow pigments, safflower yellow B and the precursor of carthamin, and carthamin itself, a red pigment, which are produced in safflower (Carthamus tinctrious L.) petals and, which have a common dimeric quinochalcone structure, is reported. The key compound for the synthesis of these analogs, (p-hydroxycinnamoyl)filicinic acid (7) was synthesized in six steps from phloroglucinol in a total yield of 39%, which was reacted with 2,3,4,5,6-penta-O-acetyl-aldehydo-d-glucose, glyoxylic acid, and ethyl orthoformate in the presence of base to afford the corresponding analog, 8, 12, 14, in good yields, respectively. Precursor analog 12 was then converted to carthamin analog 14 by oxidative decarboxylation by treatment with potassium permanganate as well as the natural specimen.     

偏最小二乘吸光光度法测定混合染料浓度

用偏最小二乘（ＰＬＳ）及阻尼因子矩阵（ＣＰＡ）吸光光度法测定混合染料浓度，两种方法所得结果相一致，用于测定四元混合染料中单一染料，结果较为满意。     

Polymerization of molecular (yellow) arsenic

DTA studies were performed to investigate the polymerization of molecular (yellow) arsenic (y-As), in the dark and also under illumination/irradiation. The semiempirical quantum chemical CNDO/BW method for calculating the dimerization reaction pathway of two As₄ molecules was applied, and showed that the stability of y-As decreases, due to the formation of stable fragments of the polymeric phase (a-As). Using the principle of orbital symmetry conservation, it was shown that polymerization takes place most favourably from a staggered “face-to-face” configuration of As₄ molecules. Dark polymerization proceeds under activation. For a result of the initial stage of polymerization, CNDO/BW simulation predicts the formation of an As₈ dimer. The molecular cluster As₈ of D_2h symmetry forms a six-membered chairshaped ring which constitutes one of the dominating units in the polymeric phase (a-As).     

A High-affinity Activator of G551D-CFTR Chloride Channel Identified By High Throughput Screening

A stably transfected CHO cell line coexpressing G551D-CFTR and iodide-sensitive yellow fluorescent protein mutant EYFP-H148Q-I152L was successfully established and used as assay model to identify smallmolecule activators of G551D-CFTR chloride channel from 100000 diverse combinatorial compounds by high throughput screening on a customized Beckman robotic system. A bicyclooctane compound was identified to activate G551D-CFTR chloride channel with high-affinity(Kd=1.8 μmol/L). The activity of the bicyclooctane compound is G551D-CFTR-specific, reversible and non-toxic. The G551D-CFTR activator may be useful as a tool to study the mutant G551D-CFTR chloride channel structure and transport properties and as a candidate drug to cure cystic fibrosis caused by G551D-CFTR mutation,     

Formation of Methylphosphonous Acid by Alkylation of Yellow Phosphorus

Methylphosphonous acid is a key intermediate in the synthesis of phosphinic acid salts, a new class of halogen-free flame retardants. This paper describes a novel and simple synthesis of this synthon: By alkylation of elemental yellow phosphorus with methyl chloride under phase-transfer conditions, methylphosphonous acid alkali salt is formed as the main product. Most of the by-products were identified. The mechanism of the reaction is discussed.