碘催化的2-炔基苯胺与二硒醚的亲电环化反应

研究了碘催化的2-炔基苯胺与二硒醚的亲电环化反应. 结果表明, 在碘单质(0.2 mmol)、 2-炔基苯胺(0.2 mmol)、 二硒醚(0.1 mmol)和甲苯(2 mL)共存体系中, 反应温度为110℃时, 2-炔基苯胺与二硒醚能发生亲电环化反应, 生成相应的3-硒取代吲哚化合物, 产率为中等到良好. 该反应在无金属催化的条件下进行, 为合成官能团吲哚提供了一种新途径.     

紫外分光光度法测定硒氧化过程中二氧化硒

利用5-硝基-2,1,3-苯并苤硒脑对紫外光的吸收特性,用紫外分光光度计测定硒氧化过程中硒(Ⅳ)含量。研究了硒(Ⅳ)与4-硝基邻苯二胺(NPDA)生成5-硝基-2,1,3-苯并苤硒脑的衍生反应条件,验证了测定结果的准确性。结果表明:衍生反应适宜条件为pH2,反应温度60℃,反应时间10 min,NPDA试剂用量为硒(Ⅳ)的168倍。在0.002~0.02 g/L硒(Ⅳ)范围内,硒(Ⅳ)浓度与衍生产物5-硝基-2,1,3-苯并苤硒脑的吸光度线性关系良好。用该法测定硒氧化过程中二氧化硒含量,RSD为0.52%。硒(Ⅳ)的平均加标回收率为98.12%。本文建立的紫外分光光度法为硒含量较大的体系中硒(Ⅳ)定量分析提供了准确、便捷的测定方法,对于其它价态硒(Ⅵ价、Ⅱ价、0价)测定有借鉴作用。     

几种菌菇中硒的荧光光度测定

菌菇试样经硝酸消化及高氯酸冒烟使有机物完全分解并将硒转化为硒(Ⅳ)离子,在微酸性的盐酸介质中,使硒(Ⅳ)与1,2-二氨基萘反应生成4,5-苯基苯并硒二唑。将此化合物萃取入环己烷中,在eλx为375~380 nm及eλm为520 nm的条件下,用1 cm石英比色皿测定其荧光强度。硒检测范围在0.001~0.10 mg.L-1内,与相应荧光强度间呈线性关系。     

二碘化钐促进的β-羟基不对称硒(碲)醚的合成

二芳基二硒(碲)醚在SmI2作用下, Se-Se(Te-Te)键还原断裂生成的硒(碲)负离子与环氧化物反应, 得到β-羟基不对称硒(碲)醚。     

用气相色谱法研究苯并苤硒脑的光解现象

以硒和2,3-二氨基萘(DAN)相互作用生成苯并苤硒脑(简称硒络物)为基本反应,用光度法、荧光法和气相色谱法测定痕量硒的方法已被广泛采用,而有关硒络物的光解性质,近年来才有一些作者揭示了这一现象。但是对此问题仍然报道不多。     

合成二苄基二硒醚的新方法

苯骈三氮唑和胺(伯、仲胺: 芳胺、杂环胺或杂环芳胺)、苯甲醛发生Mannich反应, 生成N-取代-1-苯骈三氮唑基苄胺, 它与硒氢化钠反应生成二苄基二硒醚, 反应条件温和, 产率高, 胺和苯骈三氮唑均可回收再利用。     

HPLC-DRC-ICP-MS测定富硒蔬菜中的硒形态

建立了高效液相色谱-动态反应池-电感耦合等离子体质谱(HPLC-DRC-ICP-MS)联用测定硒代胱氨酸(SeCys2)、甲基硒代半光氨酸(MeSeCys)、亚硒酸盐(SeIV)、硒代蛋氨酸(SeMet)和硒酸盐(SeVI)的方法。样品通过胃蛋白酶提取,采用Hamilton PRP X-100色谱柱(250 mm×4.6 mm,10μm),使用5 mmol/L的柠檬酸溶液(pH 4.7)作为流动相,在10 min内可以完全分离5种硒形态。在80Se质量数下,采用甲烷作为DRC反应气,可有效消除40Ar40Ar+对80Se的干扰,提高检测灵敏度。电感耦合等离子体质谱(ICP-MS)检测,各硒形态的线性相关系数均大于0.9990,Se(IV)、Se(VI)、SeMet、SeCys2、MeSeCys的定量限分别为5,10,10,5,5μg/kg,5种硒形态的加标回收率在80.1%～99.2%之间,可满足蔬菜中硒形态定量分析。     

阴离子交换色谱-电感耦合等离子体质谱法测定长期汞暴露人群硒干预后血清中的小分子硒形态

建立了阴离子交换高效液相色谱-电感耦合等离子体质谱联用测定不同形态硒的在线分离检测方法,并将其应用于长期汞暴露人群血清中小分子硒的形态研究.流动相A为0.5 mmol/L柠檬酸铵-2%(V/V)甲醇(pH 3.7),流动相B为100 mmol/L柠檬酸铵-2%(V/V)甲醇(pH 8.0);采用93%A-7%B时,硒代...     

氢氧化铯催化O,O-二烷基-Se-芳基磷酸酯的合成

在催化量氢氧化铯存在下,O,O-二烷基膦酸酯与二芳基二硒醚在DMSO中、室温、空气氛中反应,高收率得到磷酸硒酯.反应机理为氢氧化铯与O,O-二烷基膦酸酯反应生成的(RO)2P-(O)Cs+,(RO)2P-(O)Cs+亲核进攻ArSeSeAr生成磷酸硒酯和ArSe-Cs+,后者在水存在下,被氧化得到ArSeSeAr和氢氧化铯.这方法为合成磷酸硒酯提供了一条简便有效的路径.     

硒催化2-氨基苄醇氧化羰基化合成1,4-二氢-2H-3,1-苯并噁嗪-2-酮

1,4-二氢-2H-3,1-苯并噁嗪-2-酮作为一种重要的母体骨架广泛存在于生物活性化合物中。此外,在有机合成中它可作为经受热脱羧生成氮杂-邻二亚甲基苯的有效工具。文献报道的合成1,4-二氢-2H-3,1-苯并噁嗪-2-酮的方法有：2-氨基苄醇与光气或其替代物反应,钯或硫催化的2-氨基苄醇与 CO的羰基化反应,钯或硒催化的2-硝基苄醇与 CO的羰基化反应,钯催化的2-叠氮基苄醇直接羰基化反应或2-叠氮基苄醇的氮杂-维悌希(aza-Wittig)/杂累积多烯调节的环合反应,苯并呋喃酮的胺解-霍夫曼重排反应,硼氢化锂还原1,2-二氢-3,1-苯并噁嗪-2,4-二酮,以及2-羟甲基苯基氨基甲酸酯的分子内亲核取代反应。上述合成方法存在原料毒性高或成本高且来源不便、原子经济性低、有腐蚀性废物或 CO2排放、CO利用率低、催化剂昂贵且难以循环使用、反应步骤较多等缺陷,因此发展绿色、高效、经济的合成新途径具有重要意义。本文采用廉价易得的非金属硒作催化剂,用 CO作羰基化试剂, O2作氧化剂,通过硒催化2-氨基苄醇的氧化羰基化反应直接合成了目标产物1,4-二氢-2H-3,1-苯并噁嗪-2-酮。通过考察反应时间、反应温度、催化剂硒的用量、助催化剂种类及用量、CO和 O2的比例及溶剂种类等影响因素,得到了优化的反应条件,目标产物收率最高可达87%。实验证实,该 Se/CO催化体系具有相转移催化功能。反应前硒以粉末形式存在于反应体系中,为多相体系;反应开始后,硒粉参与羰基化反应形成可溶活性化合物,从而成为均相体系;反应完成后硒粉经氧化可重新从反应介质中沉淀析出,又变为多相体系。因此,该体系既实现了高效的均相催化反应,又便于催化剂分离回收,且回收的硒可重复使用,其催化活性基本保持不变。结合相关文献,我们提出了该反应的机理：在助催化剂三乙胺存在下,硒首先与 CO反应原位生成羰基硒,然后羰基硒先后接受2-氨基苄醇中氨基和羟基的亲核进攻生成目标产物,同时释放出硒化氢,硒化氢再被 O2氧化为硒,从而进入下一轮催化循环反应。总之,我们成功开发出一条绿色、高效、经济的1,4-二氢-2H-3,1-苯并噁嗪-2-酮合成新途径。用廉价易得且能循环使用的硒替代贵金属钯作催化剂,用 CO替代剧毒光气或其衍生物作羰基化试剂, O2作氧化剂,硒催化的2-氨基苄醇氧化羰基化反应可顺利进行,以87%的良好收率得到目标产物,具有成本低、原子经济性高、CO利用率高、步骤简短、无腐蚀性废物或温室气体 CO2排放、无光气使用及环境相对友好等优点。     

Impact of alkali treatment on physico-chemical,thermal, structural and tensile properties of Carica papaya bark fibers

This study aims to examine the effect of sodium hydroxide (NaOH) treatment on the physico-chemical properties, structure, thermal, tensile and surface topography of Carica papaya fibers (CPFs). The surface of raw CPFs was modified by soaking with 5% NaOH solution for 15, 30, 45, 60, 75 and 90?min. The results of thermo-gravimetric analysis revealed that the optimum treatment time for alkali treatment was 60?min. It was found that the alkali treatment improved the properties of the CPFs. The results of TGA, FT-IR, XRD and AFM suggest that the treated CPF is a suitable alternative as reinforcement in polymer composites.     

Chemometric and trend analysis of water quality of the South Chennai lakes: an integrated environmental study

In order to bring out the nature of the factors influencing lake water composition, multivariate statistical analysis and trend analysis were performed based on the hydrochemical data of the study area, namely, South Chennai. Change in land use pattern and settlements along the banks of the lakes alters the quality and quantity of the surface water. In the present study, the R‐mode factor analysis and cluster analysis were applied to the geochemical parameters of the water to identify the factors affecting the chemical composition of the lake water. Dendograms of both the seasons give three major clusters, reflecting the groups of unpolluted to moderately polluted, polluted, and heavily polluted stations. The movement of stations from one cluster to another clearly brings out the seasonal variation in the chemical composition of the lake water. The complex hydrochemical data of the surface water were interpreted by condensing them into three major factors. Factor score analysis was used successfully to delineate the stations under study and the role of the contributing factors, and the nature of factors responsible for the variation in chemical composition of the water has been clearly brought out. Results of trend analysis using ArcGIS clearly indicate that the trend in water quality is deteriorating at a faster rate in the eastern part of the study area. It is understood that although natural shifts probably can account for some of the variation, it is most likely that human activities play a major role in affecting the water quality on a regional scale. Copyright © 2014 John Wiley & Sons, Ltd.     

On-line fermentation gas analysis: Error analysis and application of mass spectrometry

On-line fermentation gas analysis is of general interest because it permits the determination of metabolic rates in almost any biological process using living organisms. The consumption and production of gases (O₂, CO₂, CH₄, etc.) and volatile compounds may be determined without causing any risk of infection. Elemental balancing permits the determination of other metabolic rates if the stoichiometry is known. This was studied with the production of poly-β-hydroxybutyrate (PHB) by Alcaligenes latus. Estimations were based on the measurement of gas partial pressure and flow-rates, pH and alkali consumption rate. Experiments with a small quadrupole mass spectrometer showed unacceptable error propagation. Therefore, dynamic error propagation for all rates was studied using simulation. It was found that, for example, a 1% relative offset-calibration error for oxygen can result in an error in PHB estimation of > 50%. It is suggested that this culture is used in combination with elemental balancing for thorough tests of the accuracy of on-line gas analysis equipment. An on-line process gas analyser based on a quadrupole mass spectrometer (Balzers PGM 407) gave the following precision values (abs. vol.?%) during cultivation of Bacillus subtilis: nitrogen (m/z 14), 0.024; oxygen (m/z 32), 0.020; argon (m/z 40), 0.0011; and carbon dioxide (m/z 44), 0.0034. These values, combined with automatic recalibration, would be sufficient for reasonable estimation of PHB, biomass and substrates.     

Determination of rank by augmentation (DRAUG)

Determining the rank of a chemical matrix is the first step in many multivariate, chemometric studies. Rank is defined as the minimum number of linearly independent factors after deletion of factors that contribute to random, nonlinear, uncorrelated errors. Adding a matrix of rank 1 to a data matrix not only increases the rank by one unit but also perturbs the primary factor axes, having little effect on the secondary axes associated with the random errors in the measurements. The primary rank of a data matrix can be determined by comparing the residual variances obtained from principal component analysis (PCA) of the original data matrix to those obtained from an augmented matrix. The ratio of the residual variances between adjacent factor levels represents a Fisher ratio that can be used to distinguish the primary factors (chemical as well as instrumental factors) from the secondary factors (experimental errors). The results gleaned from model studies as well as those from experimental studies are used to illustrate the efficacy of the proposed methodology. The method is independent of the nature of the error distribution. Limitations and precautions are discussed. An algorithm, written in MATLAB format, is included. Copyright © 2011 John Wiley & Sons, Ltd.     

新材料的发展与分析化学

文章介绍了新材料的重要性及发展方向,分析化学在新材料研制中起着耳目的作用,另一方面新材料也为分析化学的进展提供了课题与条件。微量分析、微区分析、表面分析是此领域中的重点。在未来的发展中,分析化学在材料的发展中的地位不会改变,并期待着分析灵敏度与空间分辩率的进一步提高。     

用局部拟合主成分回归计算光度分析法测定黄连生物碱

针对具有样本数据非无匀分布和非线性特点的光度分析问题，提聘种局部拟合 主成分回归法，用于中药多组分计算测定。该方法根据待测样本与各已知样本光度 分析数据的欧式距离确定相应的权值，将部分权值较大的样本组成校正集，并用分 段线性拟合算法建立待测样本的校正预测模型，将其用于分析黄连的药根碱、巴巴 亭和小檗碱等三种生物碱，所得预测均方根误差分别为0.023,0.0400和0.052，优 于主成分回归法、偏最小二乘法以及人工神经元网络法所得结果。这表明，本方法 用于中药光度分析能获得较为准确的计算分析结果。     

Determination of Mercury in Geological Materials by Continuous-Flow,Cold-Vapor,Atomic Absorption Spectrophotometry

Abstract

To determine mercury in geological materials, samples are digested with nitric acid and sodium dichromate in a closed teflon vessel. After bringing to a constant weight, the digest is mixed with air and a sodium chloride-hydroxylamine hydrochloride-sulfuric acid solution and then Hg(II) is reduced to Hg with stannous chloride in a continuous flow manifold. The mercury vapor is then separated and measured using cold vapor atomic absorption spectrophotometry (CV-AAS). For a 100 mg sample the limit of detection is 20 parts per billion (ppb) Hg in sample. To obtain a 1% absorption signal, the described method requires 0.21 ppb Hg solution (equal to 16 ppb in sample). Precision is acceptable at less than 1.2% RSD for a 10 ppb Hg aqueous standard. Accuracy is demonstrated by the results of the analysis of standard reference materials. Several elements do interfere but the effect is minimal because either the digestion procedure does not dissolve them (e.g., Au or Pt) or the; are normally of low abundance (e.g., Se or Te).     

双嘧达莫的荧光光谱分析法

以荧光光谱法研究了双嘧达莫在溴化十六烷基三甲基铵(CTMAB)、β_环糊精 (β_CD)、十二烷基硫酸钠 (SDS)等介质体系中的荧光性质 ,发现CTMAB、SDS和 β_CD对双嘧达莫均有不同程度的荧光增敏作用 ,提出了在CTMAB、SDS和 β_CD水溶液中测定双嘧达莫的荧光光谱分析法 ;该法灵敏度高 ,检出限低(3.20×10 -9mol/L) ,在6.40×10 -8～3.20×10 -6mol/L范围内荧光强度与双嘧达莫的浓度呈良好线性关系     

区分化学分析法与仪器分析法适用性的实践教学探索

根据方法原理,分析化学的常用分析方法可分为化学分析法和仪器分析法。高灵敏度、高选择性、高自动化、数字化和智能化已成为分析化学的发展方向,仪器分析法成为了分析化学发展的主流和热点。因此,在校本科生往往忽视化学分析法的重要作用以及适用范围,陷入仪器分析法为万能分析方法的误区。本文选用络合滴定法和原子吸收光谱法分别对常量含铅样品进行测试,通过考察测试结果的相对误差大小,探索了化学分析法和仪器分析法的适用范围,从而纠正了在校本科生的唯仪器分析法的错误观念。