离子色谱法测定聚合物材料中铬(Ⅵ)含量

采用离子色谱法测定聚合物材料中的铬(Ⅵ)含量。取粒径小于250μm的聚合物样品用0.5mol·L-1氢氧化钠溶液提取3h。分取适量提取液经过滤及RP柱净化后,通过IonPac AG19保护柱及DIONEX IonPac AS19阴离子分离柱分离,先后用25mmol·L-1和50mmol·L-1的氢氧化钠溶液淋洗分离柱,采用抑制电导检测器检测。铬(Ⅵ)的质量浓度在0.10~10.0mg·L-1范围内与其峰面积呈线性关系,检出限(3s/k)为7mg·kg-1。对聚氯乙烯(PVC)样品连续测定8次,测定值的相对标准偏差为9.2%。用标准加入法进行方法的回收试验,测得回收率在95.2%~105%之间。     

离子色谱法测定烟气脱硫石膏中半水亚硫酸钙的含量

用离子色谱法测定了烟气脱硫石膏中亚硫酸根的含量,并以此换算成半水亚硫酸钙的质量分数。半水亚硫酸钙在盐酸和氯化亚锡溶液中转化为二氧化硫,二氧化硫被吸收液吸收。吸收液经0.22μm的滤膜过滤后,分取25μL进样,经AS9-HC型分离柱和AG9-HC型保护柱分离,以8mmol·L-1碳酸钠-2mmol·L-1碳酸氢钠溶液为流动相进行淋洗,采用电导检测器进行检测。亚硫酸盐的质量浓度在1.00~100mg·L-1范围内与其峰面积呈线性关系,检出限(3S/N)为0.05mg·L-1。以烟气脱硫石膏样品为基体进行加标回收试验,所得回收率为97.4%和101%,测定值的相对标准偏差(n=6)在0.35%~1.4%之间。     

流动注射双柱-在线固相萃取分离-紫外分光光度法测定乳制品中三聚氰胺的含量

于在线固相萃取分离-紫外分光光度法测定乳制品中三聚氰胺(ML)含量的FIA系统中,引入了双柱结构(自制的PCX1柱和PCX2柱),并采用异步注射分析模式。调节乳制品样品酸度为pH 4.5。样品进入FIA系统后先后经过如下过程:流经PCX柱富集ML;用甲醇-水(75+25)溶液清洗150s,除去吸附在柱上的其他杂质;用氨水-甲醇-水(1+25+74)混合液洗脱ML(洗脱时间PCX1柱为36s,PCX2柱为34s);洗脱液经采样环(体积60μL)采样,0.3mol·L-1氯化铵溶液作载流,推动采样环中"样品塞"流至流通池,于237nm处进行光度检测。测得ML的质量浓度在0.50~40.0mg·L-1内与相应的吸光度呈线性关系,检出限(3s/k)为0.21mg·L-1。加标回收率在98.1%~108%之间,测定值的相对标准偏差(n=11)依次为4.2%,0.87%。     

高效液相色谱法测定植物果实中儿茶素、表儿茶素和原花青素B_2

提出了高效液相色谱法测定植物果实中儿茶素、表儿茶素和原花青素B2。样品经乙醇(6+4)溶液索氏提取后,用固相萃取技术对提取液进行净化。以SinoChrom ODS C18色谱柱为分离柱,以乙腈-0.1%(φ)磷酸溶液(15+85)为流动相进行洗脱,检测波长为280nm。3种目标分析物质量浓度的线性范围为5.0~100.0mg·L-1,方法的检出限(3S/N)在1.03~2.38mg·L-1之间。对样品进行加标回收试验,回收率在83.6%~98.5%之间,测定值的相对标准偏差(n=3)在0.4%~2.1%之间。     

高效液相色谱法测定橡胶制品中2-巯基苯并噻唑

采用高效液相色谱法测定橡胶制品中2-巯基苯并噻唑的含量。样品经丙酮超声提取两次。采用C18反相色谱柱为分离柱,以甲醇-0.01mol·L-1磷酸二氢钠(80+20)溶液为流动相,在检测波长320nm处进行测定。2-巯基苯并噻唑的质量浓度在0.10~10.0mg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)为0.54mg·kg-1。在0.10,2.0,10.0mg·L-1等3个浓度水平进行加标回收试验,回收率在85.3%~95.4%之间,测定值的相对标准偏差(n=6)在3.1%~5.6%之间。     

高效液相色谱法测定染发剂中2-硝基-p-苯二胺

应用高效液相色谱法测定了染发剂中2-硝基-p-苯二胺的含量。样品用乙醇-水(1+1)混合溶液提取后,经水系C18色谱柱分离,以(A)10mol·L-1柠檬酸缓冲溶液-10mol·L-1辛烷磺酸钠溶液(pH 2.6)与(B)乙腈以体积比75比25组成的混合溶液为流动相进行等度洗脱,用二极管阵列检测器于410nm检测。2-硝基-p-苯二胺的线性范围为2.4～240mg·L-1,检出限(3S/N)为0.7mg·L-1。以染发剂样品为基体,进行加标回收试验,回收率在90.4%～99.4%之间,相对标准偏差(n=6)在0.35%～3.0%之间。     

高效液相色谱法测定保健食品中α-硫辛酸含量

提出了高效液相色谱法测定保健食品中α-硫辛酸含量的方法。样品用乙腈-水(4+6,预调至pH 3.5)混合液超声提取25min,以C18色谱柱为分离柱,以上述乙腈-水混合液为流动相,在波长210nm处进行测定。α-硫辛酸质量浓度在20.0~500mg·L-1范围内与峰面积呈线性关系,方法检出限(3S/N)和测定下限(10S/N)分别为0.80mg·L-1和2.7mg·L-1。以空白样品为基体进行加标回收试验,所得回收率在91.5%~98.7%之间,相对标准偏差(n=5)小于5.0%。     

液液萃取-高效液相色谱法同时测定水基胶中17种邻苯二甲酸酯类物质的残留量

采用液液萃取-高效液相色谱法同时测定水基胶中17种邻苯二甲酸酯类物质的残留量。水基胶样品经水分散后,用乙酸乙酯萃取,萃取液离心后,取上层清液过0.45μm有机相滤膜。以DIONEX Acclaim explosives E2柱为分离柱,以不同体积比的乙腈和水的混合溶液为流动相进行梯度洗脱,在检测波长220nm处进行测定。17种邻苯二甲酸酯的质量浓度均在0.4~20.0mg·L-1范围内与峰面积呈线性关系,方法的检出限(3s)在0.024~0.114mg·L-1之间,测定下限(10s)在0.079~0.379mg·L-1之间。加标回收率在89.7%~101%之间,测定值的相对标准偏差(n=5)小于6.0%。     

离子色谱法测定水果和蔬菜中2,4-二氯苯氧乙酸的含量

采用离子色谱法测定水果和蔬菜中2,4-二氯苯氧乙酸的含量。水果或蔬菜样品10.0g经0.2mol·L-1硫酸溶液10.0 mL提取后,用二氯甲烷10.0 mL萃取,二氯甲烷层再用35mmol·L-1氢氧化钾溶液5.00mL反萃取,取水相,经AG-19保护柱及AS-19阴离子分离柱分离,以35mmol·L-1氢氧化钾溶液淋洗色谱柱,所得淋出液采用抑制电导检测器检测。2,4-二氯苯氧乙酸的质量浓度在5.0mg·L-1以内与其峰面积呈线性关系,检出限(3S/N)为0.05 mg·L-1。加标回收率在93.6%~105%之间,测定值的相对标准偏差(n=6)在2.1%~5.5%之间。     

高效液相色谱法测定抗癫痫类中成药中6种非法添加的化学药物

应用高效液相色谱法测定抗癫痫类中成药中苯巴比妥、苯妥英钠、卡马西平、氯硝西泮、丙戊酸钠和地西泮等6种非法添加的化学药物的含量。中成药样品经甲醇提取,所得提取液以Kromasil C18色谱柱为分离柱,用(A)0.01mol·L-1磷酸二氢钾溶液(用磷酸调至pH 2.5)-乙腈(90+10)混合溶液和(B)乙腈两者的不同比例的混合液作为流动相进行梯度洗脱,在检测波长210nm处进行测定。丙戊酸钠的质量浓度为200~4 000mg·L-1,其余5种化合物均在5~100mg·L-1范围内与各相应峰面积之间呈线性关系,方法的检出限(3S/N)在1~20mg·L-1之间。以空白样品为基体进行加标回收试验,所得回收率在98.0%~103%之间,测定值的相对标准偏差(n=6)在0.41%~1.9%之间。     

非那雄胺合成工艺改进

非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Synthesis of phenolic components of Grains of Paradise

Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared.     

Acid hydrolysis of carboxymethylcellulose of low degree of substitution

Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.     

Study of hydration of two cements of different strengths

Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, M_o, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700^oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date.     

Estimation of Kinetic Parameters of Thermal Oxidation of Ilmenite

The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of hematite Fe₂O₃. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the best fitting experimental data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanism of action of base-catalyzed oxygenation of phenol derivatives

Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6.     

氯氧化镁生成热的研究

用氧化镁氯化镁水溶液制备了8水合氯氧化镁[nMg(OH)2·MgCl2·8H2O], 并测定了其在盐酸中的溶解热, 实验结果表明, 氯氧化镁溶解热与n值呈线性关系, 根据溶解热求出5Mg(OH)2·MgCl2·8H2O和3Mg(OH)2·MgCl2·8H2O的生成热分别为-7727.1和5888.1kJ·mol^1^-。     

化学计量中不确定度评定研究进展

测量不确定度是表征合理地赋予被测量之值的分散性的参数。本文针对化学计量不确定度评定基础模型仅适用于线性模型、概率分布为正态分布或缩放位移t分布等局限,介绍了近年来不确定度评定的研究热点:蒙特卡罗方法(Monte Carlo Method,MCM),不确定度评定的来源、评定概念、评估方法及其发展过程,扩大了测量不确定度评定与表示的适用范围。