深色食用油脂中过氧化值的测定

目的 比较手动滴定法和电位滴定法对过氧化值的检测结果, 提高过氧化值测定的准确性, 探索测定深色油脂中过氧化值的适宜方法。方法 用手动滴定法和电位滴定法分别测定深色油脂和浅色油脂的过氧化值, 对检测结果进行对比, 选择最优的检测方法, 并进行方法学验证。结果 当样品为浅色样品时, 2种方法测定过氧化值的差异小, 但当样品为深色样品时, 只能用电位滴定的方法来测定, 手动滴定无法判断终点。电位滴定法加标回收实验的回收率为97.55%~104.84%, 相对标准偏差为0.9%~2.2%, 满足实验要求。结论 相比手动滴定法, 电位滴定方法更适用于食用油脂中过氧化值的测定。     

Investigation of the Complexes Formed between PARP1 Inhibitors and PARP1 G-Quadruplex at the Gene Promoter Region

DNA repair inhibitors are one of the latest additions to cancer chemotherapy. In general, chemotherapy produces DNA damage but tumoral cells may become resistant if enzymes involved in DNA repair are overexpressed and are able to reverse DNA damage. One of the most successful drugs based on modulating DNA repair are the poly(ADP-ribose) polymerase 1 (PARP1) inhibitors. Several PARP1 inhibitors have been recently developed and approved for clinical treatments. We envisaged that PARP inhibition could be potentiated by simultaneously modulating the expression of PARP 1 and the enzyme activity, by a two-pronged strategy. A noncanonical G-quadruplex-forming sequence within the PARP1 promoter has been recently identified. In this study, we explored the potential binding of clinically approved PARP1 inhibitors to the G-quadruplex structure found at the gene promoter region. The results obtained by NMR, CD, and fluorescence titration confirmed by molecular modeling demonstrated that two out the four PARP1 inhibitors studied are capable of forming defined complexes with the PARP1 G-quadruplex. These results open the possibility of exploring the development of better G-quadruplex binders that, in turn, may also inhibit the enzyme.     

增强剂YQ1210在瓦楞纸板回用过程中的应用及其电荷分析

运用正交实验对增强剂YQ1210在瓦楞纸板回用过程中的增强效果进行了初步研究.研究结果表明,当YQ1210用量为0.5%,温度55℃,反应时间120min,pH值为5时,增强效果最佳.同时,利用胶体滴定法分析了添加不同用量YQ1210时纸料的电荷特性,结果表明,当YQ1210用量为0.5%时,纸料呈现较弱的阴离子性,接近电中性,絮聚作用明显.     

Carbon and sulphur on Pd(111) and Pt(111): Experimental problems during cleaning of the substrates and impact of sulphur on the redox properties of CeOx in the CeOx/Pd(111) system

The X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and CO titration has been used to detect common impurities like carbon and sulphur on Pd(111) and Pt(111) surfaces. Different experimental problems are discussed and practical tips for the cleaning of Pd(111) and Pt(111) are given. A mechanism for the carbon oxidation on closed packed platinum group metals like Pt(111) and Pd(111) is presented. The bulk carbon concentration of Pd(111) was estimated based on the Langmuir-McLean theorem. Additionally it was shown that the titration with CO and subsequent XPS measurement is a powerful yet convenient method for quantitative detection of impurities and ceria coverage determination. A CeO_x/Pd(111) inverse model system was prepared by evaporation of cerium in an oxygen atmosphere. The comparative study has shown that sulphur contamination changes the redox properties of the CeO_x in the CeO_x/Pd(111) system.     

SPS制备纳米晶Bi_(0.75)Er_(0.25)O_(1.5)固体电解质

以分析纯Bi2O3和Er2O3为原料,采用反向滴定共沉淀法合成Bi和Er的氢氧化物前驱体,并对共沉淀的pH值条件进行了分析。将该前驱体在500℃焙烧3h后得到Bi0.75Er0.25O1.5的纳米粉体,高温XRD结果表明该粉体主要为β相,谢乐公式计算平均晶粒尺寸为10nm,并且随温度升高在650℃转变为δ相。通过热力学计算,确定了SPS下烧结Bi0.75Er0.25O1.5陶瓷适宜的温度和氧分压条件,最后在测试温度为500℃保温1min得到了相对密度达到96%的δ相纳米晶的Bi0.75Er0.25O1.5陶瓷,平均晶粒尺寸为18nm。     

微型碱式滴定管的制备及其在铅和铋含量测定中的应用

利用自制的微型碱式滴定管进行了酸碱滴定和配位滴定的微型试验研究。通过酸碱滴定试验,将自制的各种规格的微型碱式滴定管与常规碱式滴定管的分析结果进行了比较,优选出最佳装置,并将其应用于常量铅、铋的测定。结果表明,用微型滴定管所得测定结果的准确度和精密度与常量滴定法相当,并克服了常量碱式滴定管近终点液滴不易控制,废液排放量大及试剂用量大等缺点,可节省大量试剂和时间,同时大大减轻了铅等试剂对环境的污染。     

Control of particle size and carboxyl group distribution in soap‐free emulsion copolymerization of methyl methacrylate–ethyl acrylate–acrylic acid

Polymer microspheres with narrow size distribution and with carboxyl groups on their surfaces were synthesized by soap‐free emulsion polymerization of methyl methacrylate (MMA), ethyl acrylate (EA), and acrylic acid (AA), and the distribution of –COOH in the latex was determined by conductometric titration. Effects of ingredients on polymerization, latex particle size (D_p), and its distribution, and the distribution of –COOH were investigated. Results showed that monomer conversion and the amount of embedded –COOH (E_a) decreased, and D_p increased with increasing amounts of NH₄HCO₃. The amounts of surface –COOH (S_a) and water –COOH (F_a) and the number of –COOH on each square centimeter of the particles' surface (S_d) increased with increasing amounts of NH₄HCO₃ and AA. With the increase of initiator (APS) and AA, D_p deceased. E_a increased with the increase of AA. F_a increased and then remained constant, and S_d decreased with the increase of initiator. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 433–438, 2004     

中和滴定在调味品检测中的误差来源与误差分析

在调味品分析中，中和滴定是很重要的分析方法之一，本文依据理论，分析实际，对中和滴定的误差来源进行讨论。     

LiMn2O4正极材料中锰的价态分析

研究了采用计算法测定锂离子电池正极材料LiMn2O4中锰的价态的方法及测定条件。用过硫酸铵将低价锰氧化成MnO-4,以硫酸亚铁铵作滴定剂测定锰的总含量;同样以硫酸亚铁铵作滴定剂测定Mn3 和Mn4 的含量;再用乙酰丙酮作络合剂,在Mn3 存在的条件,准确测定Mn4 的含量,通过计算得出其中Mn2 、Mn3 和Mn4 各自含量,并且研究了烧结温度与锰的价态变化关系。本法对锂离子电池正极材料LiMn2O4研制有一定的指导作用。     

Comparison of techniques for chromium sesquioxide analysis in marker studies

Titrimetric, atomic absorption and plasma emission spectrometry methods are compared in the estimation of chromium from an alkaline fusion solubilisation of chromium sesquioxide (Cr₂O₃) digestibility marker in rat faeces. Considerable differences in the between-batch precision for the methods were noted. The ferrous ammonium sulphate titration showed the least imprecision (0.67% RSD) compared with 2.1% RSD for the inductively coupled plasma emission spectrometry and 4.7% RSD and 5% RSD for the atomic absorption methods of the nitrous oxide-acetylene and air-acetylene flames respectively. The atomic absorption methods were found to be highly sensitive to interferents, chromium oxidation state and changes in flame chemistry with respect to operating conditions.